Abstracts - Plasma Québec

Transcription

Plasma Quebec’16; 1 et 2 juin 2016 à l’Université de Montréal.
Radio-frequency Magnetron sputtering of ferroelectric Hf0.5Zr0.5O2 films;
Processing and characterization
F. Ambriz-Vargas1, R. Nouar2, A. Sarkissian2, R.Thomas1 and A. Ruediger1
1
Nanoelectronics-Nanophotonics, INRS-Énergie Matériaux et Télécommunications,
2
Plasmionique Inc.
1650 Lionel-Boulet, Varennes, Québec, J3X1S2, Canada
Recently, ferroelectric thin films for non-volatile semiconductor memory application was
restricted to perovskite and Aurivillius class of materials. However, these multifunctional
oxides suffer from lack of CMOS compatibility due to poor interfacing with silicon and
electrical degradation under forming gas treatment. These issues along with the inability
to down scale further preventing its use in high density memories [1]. Recent studies
showed that the ferroelectricity of Hf0.5Zr0.5O2 films may provide the solution to this
problem, according to the following reasons:
1. High compatibility with CMOS technology, nowadays the semiconductor
industry uses the binary oxide of HfO2 and ZrO2 as a high-k dielectric material for
the replacement of SiO2 in advanced semiconductor devices [2].
2. High scalability, the large band gap (Eg >5eV) of Hf0.5Zr0.5O2 films ensure more
than 1eV band offset with respect to metal or semiconductor, allowing for a
thickness reduction below 10 nm with low leakage current [3].
3. Good ferroelectric properties in ultrathin form (thickness below 3nm),
contrary to conventional perovskite materials, where ferroelectricity disappears
below a certain thickness (~ 2 nm), in these material ferroelectricity disappears
above a critical thickness (~10 nm) [3].
Owing to the importance of Hf0.5Zr0.5O2 films to the semiconductor industry, the present
work reports the radio-frequency magnetron sputtering deposition of Hf0.5Zr0.5O2 on
Pt/Al2O3/SiO2/Si substrates, where sstructural, compositional and morphological
evolutions were studied as a function of various processing parameters and thicknesses to
understand the formation of Hf0.5Zr0.5O2 and its ferroelectric properties. Such a study will
be instructive in understanding the thickness dependent ferroelectric properties of
Hf0.5Zr0.5O2.
References
1.
2.
3.
Martin, D., et al., Downscaling ferroelectric field effect transistors by using
ferroelectric Si-doped HfO2. Solid-State Electronics, 2013. 88: p. 65-68.
Müller, J., et al., Ferroelectric Zr0.5Hf0.5O2 thin films for nonvolatile memory
applications. Applied Physics Letters, 2011. 99(11): p. 112901.
Cho, D.-Y., H.-S. Jung, and C.S. Hwang, Structural properties and electronic structure
ofHfO2-ZrO2composite films. Physical Review B, 2010. 82(9).
Characterization of fibrillary structures appearing on polymeric surfaces after
femtosecond laser micromachining
.
Y. Assaf, A-M Kietzig; Department of Chemical Engineering, McGill University
Laser micromachining is a fast and contactless method to alter the topology, and thus the
properties, of a material’s surface. With the emergence of femtosecond (fs) laser technology, this
technique now allows the modification of target surfaces at the nanoscale. It has recently been
shown that, under certain circumstances, superhydrophobic fibrillary structures appear on fs
textured poly(tetrafluoro ethylene) (PTFE). Other than exhibiting altered wetting properties,
these structures also offer a much larger surface area and porosity when compared to the base
material. If these structures could be functionalized, reproduced on different polymers, or have
their properties controlled, they could be used in a very wide range of applications such as selfcleaning materials and biomedical devices. Unfortunately, current fs laser-polymer interaction
theory does not explain how and why these structures form or what their properties are. Most of
the uncertainty stems from the fact that polymers exhibit non-linear optical effects and tend to
undergo photochemical reactions during machining.
In this work, a parametric study of surface structure formation with respect to fs laser
machining parameters was conducted for a selection of different polymers. First, the standard
laser ablation models were fit against machining data for each material. Thus, several parameters
of interest such as ablation threshold fluence and incubation coefficients were obtained.
Afterwards, the polymers had their surface modified by laser area ablation and several types of
microstructures were observed and imaged. With the help of fractal and lacunarity analysis of the
images, the different structures were quantitatively compared and classified. Through that
process, fibrillary structures were confirmed to form on several polymers other than PTFE under
different conditions. As a next step, the evolution of the surface optical properties of the different
polymers as a function of machining parameters was tracked using UV-VIS spectrophotometry.
These experiments showed that the formation of such structures was accompanied with a large
increase in absorption as well as a transition from non-linear to linear light absorption for some
materials. Crystallographic measurements were further carried out in order to determine if this is
due to a local increase in crystallinity at the surface of the samples. Finally, the evolution in
chemical composition and bonding structure of the different polymers as a function of machining
parameters was also tracked using XPS. These experiments showed that the fibrillary
microstructure is susceptible to oxidation at high fluence and that polymers with high oxygen
content are less likely to form such a structure.
In conclusion, this work involved a wide parametric study of the ablation behavior of
several polymers during fs laser machining. The conditions under which different
microstructures are formed were identified for a selection of different thermoplastics. These
structures were then characterized both optically and chemically. Through these experiments, the
intrinsic physico-chemical properties of a polymer that dictate its final surface structure were
identified. Therefore, our work significantly contributes to the material selection process when
intending to machine a polymer with fs lasers for a specific application.
The Effect of Surface Chemistry on Monocyte
Adhesion to Plasma Deposited Functional Organic
Coatings
Sara Babaei1, Natalie Fekete2, Corinne A. Hoesli2, Pierre-Luc Girard-Lauriault1
1
Plasma Processing Laboratory, Department of Chemical Engineering, McGill University, Montreal, QC,
H3A 0C5, Canada
2
Stem Cell Bioprocessing Laboratory, Department of Chemical Engineering, McGill University, Montreal,
QC, H3A 0C5, Canada
Monocytes play a crucial role in inflammatory responses to implanted biomaterials. It has
been reported that the behavior of cells on a biomaterial is influenced by both their intrinsic
phenotype and their extracellular environment. Therefore, monocyte adhesion to a
biomaterial may present different characteristics and may be significantly influenced by the
chemical nature and physical microstructure of the biomaterial. In this contribution, different
plasma deposited functional organic coatings were prepared by low-pressure plasma copolymerization of binary gas mixtures constituted of a hydrocarbon (ethylene or butadiene)
and a heteroatom containing gas (ammonia or carbon dioxide) in order to deposit either
nitrogen or oxygen containing coatings. The coated surfaces were characterized using various
techniques including x-ray photon spectroscopy and ultraviolet-visible spectroscopy. The
surface charge and stability of the coatings were measured by use of electro kinetic analyser
and profilometer, respectively. The U937 myeloid cell line and NB4 promyelocytic cell line
were cultured for a period of 1h on plasma polymerized coatings with varying surface
chemistry and surface charge using cell culture medium with and without fetal bovine serum
before cell adhesion was assessed by optical microscopy. The results showed that the nitrogen
and oxygen content of the plasma polymers control the adhesion of U937 and NB4 cell lines
to the coatings, where above a threshold, the surface shows affinity towards these cell lines
irrespective of the culture medium used.
Colloque Plasma-Québec, Université de Montréal, 1-2 Juin 2016
Pulseur nanoseconde haute tension-haute fréquence à compression magnétique
pour la génération de plasma à pression atmosphérique
V. Baillard,a M.D.G. Evans,a,b, J.M. Bergthorson,b S. Coulombe,a
aPlasma
Processing Laboratory, Département de génie chimique, Université McGill
bAlternative
Fuels Laboratory, Département de génie mécanique, Université McGill
Les activités de recherche sur les décharges électroluminescentes entretenues par l’application
d’impulsions courtes à forte tension se sont intensifiées, et en particulier pour les applications en combustion
assistée par plasma1 (CAP) et en allumage de flamme2. La CAP s’effectue dans des mélanges de carburants et
d’oxydants à des pressions de quelques dizaines d’atmosphères. Ces conditions d’opération imposent des
seuils de tension élevés et la nécessité de produire des décharges non-thermiques de grands volumes impose
des contraintes sur la durée des impulsions. Les générateurs d’impulsions courtes (10-1000 ns) à forte
amplitude de tension permettent d’obtenir cette réactivité chimique à basse température. Ces générateurs
permettent également de contrôler la quantité d’énergie injectée dans la décharge et de minimiser la
conversion en énergie thermique. Cette affiche présente les travaux menés sur l’élaboration et la construction
d’une nouvelle source d’impulsions courtes à haute tension et haute fréquence, utilisant la technologie de
compression magnétique pour l’application à la génération de plasma non-thermique à haute pression.
Le principe physique à l’œuvre dans le générateur d’impulsions est la très forte variation de
l’inductance à un temps spécifique d’application de tension qu’offre un inducteur à cœur ferromagnétique3
(∆L/L > 1000). Ces inducteurs sont ici utilisés comme interrupteurs non-conventionnels pour transférer
l’énergie de chaque impulsion à travers les différentes sections de l’appareil. Le circuit est construit en trois
parties. La section à Basse Tension utilise des transistors IGBT pour décharger un condensateur de 1 mF à une
fréquence fixe, qui délivre une impulsion de courant de quelques μs et de plus de 150 A. La section de
Compression Magnétique transforme cette impulsion en augmentant sa tension et en réduisant sa durée par
l’utilisation de transformateurs saturables. Enfin, la section de Haute Tension double la tension de l’impulsion
finale, tout en effectuant une dernière étape de compression magnétique, et l’applique à la charge en fin de
ligne.
Des expériences furent menées avec une charge de 3000 Ω, en y appliquant des impulsions de plus de
20 kV, à une fréquence de plusieurs dizaines de kHz. La durée totale à mi-hauteur de l’impulsion est de moins
de 150 ns, pour toute la gamme de tension disponible.
Références
1. S. Nagaraja, T. Li, J. A. Sutton, I. V Adamovich, V. Yang, Proc. Combust. Inst. 35 (2015) 1–22.
2. D. R. Singleton, A. Kuthi, J. M. Sanders, M. A. Gundersen, A. Simone, S. J. Pendleton, IEEE Trans. Dielectr. Electr. Insul. 18
(2011) 1084–1090.
3. W. C. Nunnally, Los Alamos, Magnetic Switches and Circuits (1982)
Caractérisation de la génération de bulles lors de l’ablation laser des nanoparticules d’or
en solution
A. Berchtikou, Esen Sokullu, Marc Andre Gauthier and T. Ozaki
Institut national de la recherche scientifique – Centre Energie, Matériaux et Telécommunications, 1650 Lionel-Boulet, Varennes,
Québec J3X 1S2, Canada
Author e-mail address:[email protected]
Résume
Le principe du traitement par choc laser consiste à induire un effet purement mécanique
dans un matériau à partir de la détente d’un plasma généré à sa surface par un
rayonnement laser impulsionnel (quelques ns et quelques GW/cm2). L’énergie laser est
absorbée dans une très faible épaisseur du matériau (nanoparticules d’or) à traiter qui est
rapidement vaporisée et ionisée. La détente de cette vapeur partiellement ionisée
provoque alors, par effet de recul, une pression qui est appliquée à la surface
nanoparticules d’or. L’expansion du plasma dans les liquides est accompagnée par la
production de bulles qui sont formées lors de la vaporisation du liquide en contact avec le
plasma chaud. Ces bulles coalescent très rapidement pour produire une grosse bulle
unique appelée bulle de cavitation. Il a été découvert que le rayon de la bulle de
cavitation ainsi que son temps de vie étaient dépendants de l’énergie laser, de l’épaisseur
de la cible et sa concentration.
Laser-induced Breakdown Spectroscopy for Efficient High-order Harmonic
Generation
M. A. Fareed, A. Berchtikou, N. Thiré, S. Mondal, B. E. Schmidt, F. Légaré, and T. Ozaki
Institut national de la recherche scientifique – Centre Energie, Matériaux et Telécommunications, 1650 Lionel-Boulet, Varennes, Québec J3X
1S2, Canada
Author e-mail address: [email protected]
High-order harmonic generation from laser-ablated plumes has been demonstrated to be an
efficient technique to generate ultrashort pulses of extreme ultraviolet radiations with high
photon flux [1,2]. In this technique, a heating pulse (called prepulse) is used to ablate plasma
plume from the surface of a solid material. Then this plasma is cooled down for few tens of
nanoseconds to produce the neutrals in the plasma plume. Finally, an ultrashort laser pulse
(called main pulse) irradiates this plume to generate high-order harmonics [3].
For the laser-ablation, information of the laser-ablated species is essential to study the
characteristics of high-order harmonics generated with the main pulse. Then, density of the laserablated species is controlled by changing laser-ablation parameters to produce high-order
harmonic with high photon flux. We use laser-induced breakdown spectroscopy to study the
characteristics of laser-ablated plumes and then find optimum laser-ablation parameters to
generate efficient high-order harmonics.
In this work, we present our results of high-order harmonics from laser-ablated graphite plume.
Information of the laser-ablated species is collected with the time-resolved laser-induced
breakdown spectroscopy and high-order harmonic flux is optimized for different main pulse
wavelengths ranging from 0.8 µm to 1.71 µm. We have observed that by choosing appropriate
laser-ablation parameters, we can generate highly efficient sub-100 eV high-order harmonics
from diatomic carbon molecules that are ablated with the prepulse from solid graphite
target [4,5].
References
[1]
[2]
[3]
[4]
[5]
R. A. Ganeev, L. B. Elouga Bom, J. Abdul-Hadi, M. Wong, J. Brichta, V. Bhardwaj, and T. Ozaki, Phys. Rev. Lett. 102,
013903 (2009).
T. Ozaki, R. A. Ganeev, M. Suzuki, and H. Kuroda, in (In Tech, 2010).
R. A. Ganeev, M. Suzuki, M. Baba, H. Kuroda, and T. Ozaki, Opt. Lett. 30, 768 (2005).
M. A. Fareed, S. Mondal, Y. Pertot, and T. Ozaki, J. Phys. B At. Mol. Opt. Phys. 49, 035604 (2016).
M. A. Fareed, N. Thiré, S. Mondal, B. E. Schmidt, F. Légaré, and T. Ozaki, Appl. Phys. Lett. 108, 124104 (2016).
Effects of irradiation parameters on femtosecond laser micromachining of metals
S Biswas, A-M Kietzig
Department of Chemical Engineering, McGill University, 3610 University Street, Montreal, Quebec,
Canada H3A OC5
Abstract: Over the years, femtosecond (fs) laser micromachining has evolved as a novel and versatile
technique for modifying optical, chemical and other material properties by creating various types of
microstructures on a material. The microstructures are formed as a result of the laser-material
interaction and ablation mechanisms that are governed by the material properties, the laser beam
parameters and the micromachining parameters. Several reports already exist elaborating on the effects
of scanning velocity, number of pulses, number of overscans, laser fluence and pulse width. However,
reports on the effects of repetition rate are hard to find and the existing ones are mostly based on single
spot experiments and compare the ablation depth and ablation rate between wide repetition ranges. Our
work thus contributes to the current state of knowledge with investigating microstructure formation in
line and area scans at 1 and 10 kHz repetition rate. A Ti: sapphire laser system having a maximum
output power of 4 W and operating at a wavelength of 800 nm, repetition rate of 1 kHz and pulse
duration of <100 fs was used to micromachine square patches on Titanium (Ti) and Copper (Cu)
samples in air. In total, three processing parameters (the power, the scanning velocity and the line
overlap) were varied, and various types of microstructures (e.g. ripples, bumps, holes and chaotic
microstructures) were obtained. The accumulated fluence over a single line scan (F∑pulse,max) and the
total fluence over the irradiated area patch (F∑line,max) were calculated. The structure types were
categorized based on scanning electron microscopy images. The different types of microstructures were
plotted as a function of F∑line,max versus F∑pulse,max. These plots were compared to results previously
obtained from micromachining the same materials at 10 kHz repetition rate (Ahmmed, Ling et al.
2015)
On Cu, the microstructures were obtained at slightly higher accumulated fluence values when
micromachined at 1 kHz than at 10 kHz repetition rate, in contrast to the microstructures obtained on
Ti, which were obtained at lower accumulated fluence. Our results indicate that the effect of repetition
rate on the micromachining outcome depends on the underlying material characteristics, such as the
thermal conductivity and the resolidification time. Ti has a low thermal conductivity and a long
resolidification time due to which the laser-induced melt layer persists for longer than in the case of Cu.
When micromachined at 10 kHz, where the consecutive pulses arrive 10 times faster than at 1 kHz, the
melt layer acts as a liquid dielectric for the subsequent pulses thereby increasing the threshold value.
Whereas, when micromachined at 1 kHz, the subsequent pulses arrive after the resolidification has
already taken place. In Cu, however, due to its high thermal conductivity and long resolidification time,
the metal-dielectric like phase transition is not observed and thereby increasing the repetition rate
decreases the ablation threshold.
In conclusion, the effect of repetition rate on micromachining has been shown by comparing the
microstructures produced at two different repetition rates. The significant differences in the
micromachining outcome at the two repetition rates have been explained on the basis of a combined
effect of the repetition rate and the material properties.
References
Ahmmed, K. M. T., et al. (2015). "Introducing a new optimization tool for femtosecond laser-induced surface
texturing on titanium, stainless steel, aluminum and copper." Optics and Lasers in Engineering 66: 258-268.
Eichstädt, J., et al. (2013). "Determination of irradiation parameters for laser-induced periodic surface
structures." Applied Surface Science 264: 79-87.
Transition de basses à hautes fréquences d’une décharge à
barrière diélectrique en hélium à pression atmosphérique
Jean-Sébastien Boisvert1,2, Joëlle Margot1 et Françoise Massines2
1Département de Physique, Université de Montréal, 2900 Blvd Édouard-Montpetit, H3T
1J4, Montréal (Qc), Canada
2PROMES-CNRS, Rambla de la Thermodynamique, 66100, Perpignan, France
Courriel: [email protected]
Les décharges à barrière diélectrique sont reconnues pour pouvoir générer des
décharges homogènes à la pression atmosphérique. Dans une configuration plan-plan
(avec 2 mm d’épaisseur de gaz) et avec une barrière diélectrique sur chaque électrode,
une décharge homogène peut être générée lorsque la tension appliquée sur le gaz est
suffisante. Par exemple, c’est le cas lorsque l'onde d'excitation sinusoïdale est d'une
fréquence de 25 kHz et que l'espace gazeux est rempli d'hélium dans un mélange de
Penning avec de l'azote. Ces conditions permettent de produire une décharge
luminescente (APGD), typique pour une excitation de basses fréquences. Dans les
mêmes conditions, lorsque la fréquence est de 13,56 MHz, dans la plage des hautes
fréquences, la nature de la décharge est complètement différente. On parle plutôt d'un
plasma continu fluctuant entre deux gaines oscillantes. Ce comportement est identifié à
une décharge capacitive (CCRF) dans le régime α.
Dans cette contribution, nous étudions la transition au cours de laquelle la décharge
passe d'une APGD en basse fréquence à une décharge en régime RF-α. L'imagerie rapide
est utilisée comme diagnostic principal pour visualiser cette transition. À partir de 100
kHz, la décharge n'est plus purement en régime luminescent. Cette transition survient
lorsque le temps de pause entre deux demi-périodes d'oscillation est trop court pour
que les pertes par recombinaisons soient significatives dans la colonne positive. Ce
comportement donne lieu à un mode hybride qui est maintenu jusqu'à environ 5 MHz,
fréquence à partir de laquelle la décharge montre clairement un régime RF-α. De plus,
lorsque la fréquence se situe dans la plage des moyennes fréquences (0,3 à 3 MHz) le
mode Ω peut être maintenu pour de faible tension appliquée.
La spectroscopie d'émission optique est utilisée pour comparer les différents régimes
de décharge obtenus. Alors que les régimes luminescent et RF-α sont très semblables, le
spectre de la décharge en régime Ω est très différent. Plus précisément, le rapport des
émissions d'hélium sur celles des impuretés (majoritairement OH, N2 et N2+) est
beaucoup plus faible dans ce régime qu'en régime luminescent et RF-α. Ce qui indique
que le rôle des électrons énergétiques par rapport au rôle des atomes dans un état
métastable est significativement plus faible en régime Ω. Autrement dit, la température
électronique devrait y être plus faible.
Spatio-Temporal Confinement of Airy Bullets
Domenico Bongiovanni1, Benjamin Wetzel1, Yi Hu2, Zhigang Chen2,3 and Roberto Morandotti1
1
INRS-EMT, 1650 Blvd. Lionel-Boulet, Varennes, Québec J3X 1S2, Canada
The MOE Key Laboratory of Weak-Light Nonlinear Photonics, TEDA Applied Physics Institute and School of
Physics, Nankai University, Tianjin 300457, China
3
Department of Physics & Astronomy, San Francisco State University, San Francisco, CA 94132, USA
2
Interest in Airy beams has steadily increased over the last few years due, to their peculiar characteristics,
such as accelerating propagation trajectories featuring non-dispersion along with self-healing properties.
These beams are relevant for both fundamental optics research and for practical applications in several
fields including, for instance, the generation of curved plasma channels and optical trapping. The
trajectory followed by a propagating Airy beam is parabolic and the beam does not undergo diffraction
along one or two spatial dimensions. Similarly, an optical pulse featured by an Airy temporal profile is
not affected by dispersion during its propagation (i.e. its temporal shape remains unchanged). Combining
such confinements, both in time and space, it is possible to generate a 3D-confined accelerating optical
beam, which does not diffract/disperse along any coordinate; such a wave packet is called
Airy Bullet (AB). We present a numerical study of AB dynamics, providing a technique capable of
optimizing the power features associated to the spatio-temporal confinement of the bullet. In particular,
we show that by reshaping the initial spatio-temporal spectrum of the AB we can obtain a maximal
overlap with the spectral content of the main lobe, resulting in overall enhancement of the spatio-temporal
energy confinement and peak intensity of the bullet.
Modèle collisionnel radiatif dépendant du temps pour l’hélium
C.Boukandou Mombo,∗ J.Claustre, R. Jbilat, F. Vidal, and J-P. Matte
Institut National de la Recherche Scientifique-Centre Énergie, Matériaux et Télécommunications,
1650 boul. Lionel Boulet, Varennes, Québec, Canada J3X 1S2
Un modèle collisionnel radiatif (MCR) est un outil servant à la description des plasmas. Il permet
entre autre d’avoir une meilleure compréhension de leur physique et l’optimisation de leurs paramètres
expérimentaux. La solution du MCR permet de connaître la fonction de distribution électronique en
énergie, les densités des différents états atomiques excités ainsi que les densités des ions atomiques
et moléculaires présents dans le plasma.
À cet effet, dans le but de mieux comprendre la physique de l’hélium en présence de sources
variant rapidement dans le temps, nous avons développé un MCR en 0-D (sans dépendance spatiale)
dépendant du temps. Celui-ci résout l’équation de Boltzmann temporelle pour décrire la cinétique
des électrons créés lors de la décharge, un ensemble d’équations de taux pour déterminer les populations des 42 premiers niveaux excités de l’atome d’hélium, des ions atomiques He+ , des ions
∗
moléculaires He+
2 et des excimers He2 . Il considère également tous les processus collisionnels im-
pliquant les électrons (ionisation, recombinaison, excitation, collisions superélastiques et élastiques,
diffusion ambipolaire, etc.) et les processus radiatifs.
Les résultats obtenus avec ce modèle sont illustrés à travers deux exemples. Le premier est une
comparaison des densités de métastables obtenues numériquement avec celles mesurées expérimentalement. Le deuxième exemple concerne un problème de post-décharge. Dans ce dernier cas, nous
montrons que la densité de métastables peut fortement augmenter dans ce régime.
[1] L.L Alves, G. Gousset, and C.M. Ferreira, A collisional-radiative model for microwave discharges in
Helium at low and intermediate pressures 25, 1713 (1992).
[2] M. Santos, C. Noël, T. Belmonte, and L. L. Alves, Microwave capillary plasmas in helium at atmospheric
pressure, 47, 265201 (2014).
∗
[email protected]
Spatial Mapping of Nanoplasmonic-Induced Photothermal Effects
in the THz Regime
Holger Breitenborn,1,* Anna Mazhorova,1 Rafik Naccache,2 Matteo Clerici,3 Larousse Khosravi Khorashad,4
Alexander O. Govorov,4 Luca Razzari,1 Fiorenzo Vetrone,1,5 Roberto Morandotti1,*
INRS-EMT, 1650 Boulevard Lionel-Boulet, Varennes, Québec J3X 1S2, Canada; 2Department of Chemistry and Biochemistry, Concordia
University, Montréal, Québec H4B 1R6, Canada; 3School of Engineering, University of Glasgow, Glasgow, G12 8LT, United Kingdom;
4
Department of Physics and Astronomy, Clippinger Research Labs, Ohio University, Athens, Ohio 45701, United States of America; 5Centre for
Self-Assembled Chemical Structures, McGill University, Montreal, Québec H3A 2K6, Canada;
* [email protected], [email protected]
1
We have developed a novel temperature mapping technique exploiting the high sensitivity of terahertz (THz)
waves to aqueous media. This method allowed us to investigate nanoplasmonic-induced photothermal effects such
as collective heating phenomena in porcine skin. Nanoparticles possess unique optical and photothermal properties
because they are capable of confining resonant photons in response to specific wavelength excitation, a process
known as surface plasmon resonance (SPR) effect. One of the most interesting features of the SPR effect is that the
strongly absorbed light is followed by a rapid dephasing of the coherent electron motion in tandem with a rapid
energy transfer to the lattice resulting in an elevation of temperature otherwise known as collective plasmonic
heating or photothermal effect. This effect is promising for a myriad of applications including therapeutic uses such
as hyperthermia [1]. In this work, we report the first instance of a THz-based technique for performing a spatially
resolved temperature mapping investigation of the plasmonic heating effect of an aqueous gold nanorod (GNRs)
dispersion in a biological model system (porcine skin). Spatially resolved thermal mapping of the GNR injection site
was achieved using a THz raster scanning technique, where the beam was scanned across the skin sample with a
resolution close to diffraction limit (300 µm). The measurements of the change in temperature were done following
an injection of a GNR dispersion in a porcine skin sample under plasmonic photoexcitation at 17 and 38 W/cm2
respectively (Fig.1).
Figure 1 (a) Digital photograph of a porcine skin sample in which GNRs were injected. The red ellipse marks the injection site in
the skin. Thermal image maps ((b) and (c)) were obtained following a plasmonic photoexcitation at 17 W/cm2 and 38 W/cm2
excitation power densities respectively, showing a maximal 16 ºC localized temperature rise at the injection site, allowing the
skin sample to reach the maximum temperature of ~ 53 ºC.
This essentially translates to a biological thermal imaging system in the temperature range of ~ 25-60 °C. Highly
localized plasmonic heating is observable and mainly concentrated around the injection site. At a lower power
density (17 W/cm2), no significant rise in skin temperature at the injection site were observed (Figure 1b). At
38 W/cm2, a highly localized temperature rise of 16 ºC at the GNR injection site were recorded, allowing the skin
sample to reach a maximum temperature of ~ 53 ºC (Figure 1c).
We noticed that the observed highly localized thermal effects must also be attributed to the collective heating
effects of the GNR dispersions that can collectively induce a significant change in temperature. Our experimental
findings were numerically proven by a realistic model based on the Navier-Stokes and thermal transfer
equations [2]. At an excitation power density of 38 W/cm2, we theoretically predicted a temperature increase of
14 ºC relative to the background, which was in good agreement with our experimental results. The collective heating
regime provides an excellent opportunity to controllably increase the temperature of a macroscopic region of tissue
without thermal damage to cells and surroundings. The correlation of THz non-invasive imaging to temperature
measurements allows us to develop a biological THz-based thermometer, so called “teramometer”.
References
[1] Jain, P. K., Huang, X., El-Sayed, I. H. & El-Sayed, M. A. “Noble metals on the nanoscale: Optical and photothermal
properties and some applications in imaging, sensing, biology, and medicine.” Acc. Chem. Res. 41, 1578-1586 (2008).
[2] Richardson, H. H., Carlson, M. T., Tandler, P. J., Hernandez, P., Govorov, A. O. “Experimental and theoretical studies of
light-to-heat conversion and collective heating effects in metal nanoparticle solutions.” Nano Lett. 9, 1139-1146 (2009).
Study of N-rich Plasma Polymer Films as a Biomaterial for Endovascular
Coiling
Madhuwanthi Buddhadasa*, Sophie Lerouge**, Pierre-Luc Girard-Lauriault*
*Plasma Processing Laboratory, Department of Chemical Engineering, McGill University,
Montreal, QC, Canada
**Laboratory of Endovascular Biomaterials (LBeV), CHUM research Centre (CRCHUM) &
Department of Mechanical Engineering, ÉTS, Montreal, QC, Canada
Endovascular coiling is the commonly used treatment technique for a brain aneurysm, a focal
dilation of an artery in the brain. It involves the placement of platinum based coils such as,
Guglielmi detachable coils (GDCs), in the aneurysm which promotes thrombosis within,
separating it from the main blood flow and preventing it from further growth and rupture. Due to
several reasons, one of which could be the relative inertness of Pt, complications such as,
recanalisation of the aneurysm leading to regrowth and rupture, may take place. This has been a
motivation for our interest in studying the feasibility of employing a plasma polymer (PP) as a
coating on the existing standard GDCs, in order to improve the healing and cure of aneurysms by
endovascular coiling. We choose to study N-rich PP films, more specifically films containing
amine functionalities which, owing to their positive charge under aqueous media of
physiological pH, are found to attract negatively charged biological species such as blood plasma
proteins. These PPs are deposited in a plasma enhanced chemical vapour deposition system,
utilising a hydrocarbon (HC) gas such as, ethylene, 1,3-butadiene or a mixture of both, and a
functional group containing gas, ammonia. Plasma parameters such as gas flow rates, gas flow
ratio and plasma power have been optimised to yield coatings with high amine content as well as
those that are stable in aqueous media which would be a vital requirement for bio-applications.
In this work, our aim is to study the thrombogenicity and relevant mechanical properties such as
friction and resistance to wear against a microcatheter material surface, of these PP films,
deposited using different HC gases and compare them with Pt surfaces. As a first step towards
thrombogenicity testing, we performed protein (fibrinogen) adsorption experiments using surface
plasmon resonance spectroscopy which allows one to investigate the kinetics of protein
adsorption in real time, determine the adsorbed layer thickness and surface density. Study of
these properties will be important to initiate the development of a suitable plasma polymer
coated GDC for the treatment of brain aneurysms.
Rotational and vibrational temperatures in DBD’s for material processing:
application to the paper plasma treatment.
A. Ionascut-Nedelcescu1, A. M. Cardini1
1 Bishop’s
University, Department of Physics, 2600 College, Sherbrooke, Qc., J1M1Z7, Canada.
In this work, a detailed analysis of the rotational and vibrational temperatures (Tr
and Tv) of an atmospheric pressure DBD plasma is presented in conjunction with
the analysis of plasma treated paper sheets. Both Tr and Tv are deduced from the
resolved spectra, by employing the Boltzmann plot method. For Tr the First
Negative System of the N2+, B (2∑u+, v=0) → X (2∑g+, v=0) transition is used,
while for Tv the (2, 5), (1, 4), and (0, 3) transitions of the N2 Second Positive
System, C3Πu → B3Πg are employed. In the first part, an analysis of the main
excitation mechanisms with emphasis on the rotational band of the molecular
nitrogen ion is presented. In the second part, the variation of both Tr and Tv with
plasma’s applied voltage is analysed. In the third part a series of identical paper
samples are treated in the same voltage range as that employed for Tr and Tv.
Optical microscopy is used to analyze the effect of the plasma on the samples
surfaces. Randomly distributed pores are noticed to appear on the surface. In order
to quantify the effect of the plasma treatment on the samples, the total area of the
pores relative to the whole treated area, is analyzed. It is noticed that neither Tr nor
Tv are affected by the voltage, in the range of values studied here, while the total
area of the pores is voltage dependent. Finally, it is concluded that the major effect
of the plasma on the samples is predominantly due to the electrons, while the
heavy particles contribution is negligible.
VO2 based light-weight tunable radiator for space applications
J. Chaillou1, A. Hendaoui2, N. Émond1, B. LeDrogoff1, É. Haddad3, M. Chaker1
1INRS
– Centre Énergie, Matériaux, Télécommunications, Varennes (Canada)
2Alfaisal University, Riyadh (Saudi Arabia)
3MPB Communications Inc., Pointe-Claire (Canada)
In the last decade, the market of nanosatellites (<10kg) skyrocketed with tens of
launches each years. While in orbit, the external temperature vary between -150°C and
150°C, it is thus imperative to regulate the internal temperature of the satellite between
-10°C and 30°C to ensure reliable operation of the electronic equipment. Thermal control
devices are actually made of bulk metal and are mechanically actuated, so they are not
suitable for nanosatellites as they increase both the satellite weight and energy
consumption.
An innovative approach, the smart radiator device (SRD), has been developed for
the nanosatellite passive thermal control. It consists of a thin “smart” coating relying on
vanadium dioxide (VO2) phase transition. This thermochromic material abruptly changes
from an IR-transparent semiconducting state to an IR-reflecting metallic state at a
temperature TSMT around 68°C. The SRD is made of an IR-reflecting substrate, a quarterwave layer (λ/4) made of an IR-transparent material and a very thin film of thermochromic
VO2. Across VO2 phase transition, the device switches from a low-emissivity state to a
high-emissivity state.
The feasibility of such SRD has already been demonstrated [1]. In this work, we
use mirror-polished aluminium as a reflecting substrate. We demonstrate how the device
performance could be enhanced by using a highly IR-transparent material (CaF2) as a λ/4
layer to achieve a large contrast between the low temperature emissivity (εL≈0.20) and
the high temperature emissivity (εH≈0.73). Finally, we have developed an IR-transparent
and UV-Vis multilayer reflective filter that reduces the heat intake generated by
exposition to sunlight, making our SRD more thermally efficient. Amorphous silicon was
selected as high-index material and CaF2 as low-index material.
[1] A. Hendaoui et al. Applied Physics Letters 102, 061107 (2013)
Modèle avancé pour la résolution numérique de l’équation de Boltzmann
dépendant du temps pour les plasmas froids d’hélium
J. Claustre, C. Boukandou-Mombo, R. Jbilat, J.-P. Matte, F. Vidal
INRS - Énergie, Matériaux et Télécommunications, Varennes, Québec.
Nous présentons ici un modèle unique pour la simulation de plasmas de décharges pour le
gaz d’hélium, i.e avec un faible degré d’ionisation et ou les espèces neutres et les ions ont une
température nettement plus faible que celles des électrons. Deux équations sont résolues dans ce
modèle: La résolution de l’équation de Boltzmann dépendant du temps, à partir de laquelle la
fonction de distribution en énergie des électrons est obtenue, et l’équation d’évolution des populations des différents états excités (i.e. aussi appelée équation de taux) de l’hélium. Une des
difficultés dans la simulation de tels plasmas est due au grand nombre d’états atomiques excités
qui doivent être pris en compte ainsi que les sections efficaces des nombreux processus qui interviennent (incluant les collisions d’excitation-déexcitation, d’ionisation, de recombinaison, les processus radiatifs, l’absorption de l’énergie électromagnétique, etc.) et ceci de manière appropriée
[1]. De plus, nous avons développé un schéma d’interpolation qui satisfait la conservation des
grandeurs physiques (i.e. conservation de l’énergie et des particules) pour tous les processus ayant
lieu dans le plasma d’hélium et qui permet de prendre correctement en compte les bonnes valeurs
des seuils d’énergies pour chaque processus décrit sur une grille discrétisée en énergie, ce qui n’est
généralement pas le cas dans les modèles existant cités dans la littérature. Un des résultat majeur
de ce modèle est la caractérisation en fonction du temps des populations (tel que les métastables
ou les dimers) dans les plasmas pulsés, i.e. plasmas largement utilisés dans de nombreuses applications industrielles et de recherche depuis un peu plus d’une dizaine d’année. Depuis peu de
temps, plusieurs groupes de recherche s’intéressent aux plasmas pulsés haute fréquence (pulsations de l’ordre de dizaines de nanosecondes) [2]. Nous illustrons certains résultats de ces plasmas
hautement dépendant du temps.
[1] M. Santos and C. Noel and T. Belmonte and L. L. Alves, J. Phys. D: Applied Physics 47,
26520 (2014)
[2] J.L. Walsh , F. Iza , and M.G. Kong Eur. Phys. J. D 60, 523-530 (2010)
Epitaxially stabilized thin films of the potentially multiferroic materials ε-Fe 2 O3 and
ε-Alx Fe 2-x O3 .
1
1
L. Corbellini , C. Harnagea , C. Lacroix2 , D. Menard3 and A. Pignolet1
1
Institut National de la Recherche Scientifique, Université du Québec
Varennes, Québec, Canada J3X 1S2
2
Department of Electrical Engineering, Polytechnique Montréal,
Montréal, Québec, Canada H3C 3A7
3
Department of Engineering Physics, Polytechnique Montréal,
Montréal, Québec, Canada H3C 3A7
ε-Fe2 O3 is a metastable intermediate phase of iron (III) oxide, between maghemite (γFe2 O3 ) and hematite (α-Fe2 O3 ). Epsilon ferrite has been investigated essentially because
of its ferrimagnetic ordering with a Curie temperature of circa 500 K [1]. However, given
its orthorhombic crystal structure that belongs to the non-centrosymmetric and polar
space group Pna21 , it should exhibit ferroelectric behavior along with magnetoelectric
coupling of the two orders (potentially making it one of the few room temperature
multiferroic materials) [2, 3]. Moreover, the material is characterized by strong magnetic
anisotropy, resulting in a ferromagnetic resonance (FMR) frequency in the THz range in
the absence of magnetic field and at room temperature. This is of particular interest given
its potential use in short-range wireless communications (e.g. 60GHz WiFi) and ultrafast
computer non-volatile memories [4, 5].
Due to its metastable nature, ε-Fe2 O3 needs to be stabilized at room temperature: to date
such feature has been obtained mainly by synthesizing it by sol-gel as nanoparticles
embedded inside a SiO2 matrix, with the stabilization mechanism being either pressure or
size confinement (or both). Recently however, deposition of epitaxial thin films of εFe2 O3 on SrTiO3 (111) was demonstrated [6]; in this case the stabilization is thought to be
due to both epitaxial strain and interface interaction between the substrate and the film.
We report the growth by Pulsed Laser Deposition of epitaxial thin films of ε-Fe2 O3 and
ε-Alx Fe2-x O3 on different single crystal substrates, both oxides (SrTiO3 , LaAlO3 , LSAT,
and YSZ) and non-oxides (single crystal Silicon), and discuss the influence of the chosen
substrate and of aluminum doping on the structural, magnetic and dielectric properties. In
particular, we focused our attention on the effect of Al inclusion inside the ε-Fe2 O3
lattice, which should result (i) in the improvement of the electric properties, given the
good ferroelectric properties of the isostructural AlFeO3 , and (ii) in a lowering of the
FMR frequency due to non-magnetic nature of Al.
[1] S. Ohkoshi et al., Angew. Chem. Int. Ed. 46, 8392 (2007);
[2] E. Tronc et al., J. Solid State Chem. 139, 93 (1998);
[3] M. Gich et al., Nanotechnology 17, 687 (2007);
[4] M. Nakajima, A. Namai, S. Ohkoshi, T. Suemoto, Optics Express 18, 18260 (2010);
[5] C.H. Back et al., Science 285, 864 (1999);
[6] M. Gich et al., Appl. Phys. Lett. 96, 112508 (2012).
[5] S. Ohkoshi, et al., J. Am. Chem. Soc. 131, 1170 (2009).
Modeling of electromagnetic near field interactions with anisotropic materials in TipEnhanced Raman Spectroscopy
C. Dab1, G. Kolhatkar1, J. Plathier1, and A. Ruediger1
1
Institut National de la Recherche Scientifique – Centre Énergie, Matériaux, Télécommunications,
1650 Boulevard Lionel-Boulet, Varennes, Québec, J3X 1S2, Canada
Contact author: [email protected]
Abstract
Tip-Enhanced Raman Spectroscopy (TERS) is a very promising field of research that
has attracted increasing attention over the last few years [1]. This technology combines
the strengths of scanning probe microscopy with those of optical spectroscopy to achieve
a high spatial resolution and signal amplification. TERS consists in externally focusing a
laser beam on a metallic tip generating an amplified optical near field [2]. The structural
and chemical properties of Raman-active nanomaterials can then be studied in depth.
In this work, we numerically simulate the electric amplification of a gold tip on
PbTiO3 using FEM numerical method for both the ferroelectric and the paraelectric
phase. We present an in depth study of the effect of the tip parameters on the electrical
field. We focus on gold as the noble metal composing the tip due to its plasmonics
propreties in the visible to near infrared (NIR) and the fact that it is still the material of
choice in most TERS experiments due to the chemical instability. The dielectric function
of gold has a large negative part with a small imaginary part in this spectral rang, leading
to strong enhancement radii in the range of typical scanning probe tips. Lead titanate
PbTiO3 thin film grown on a platinum island were used as sample surface in this study.
PbTiO3 is known to be a ferroelectric room temperature with a possible size-driven phase
transition into the paraelectric phase . Our simulations confirms the known dependence of
the surface plasmon polariton peak as a function of distance and in addition shows that
typical experimental configurations should be sensitive to changes of refractive index of
about 10% as e.g. observed between the ferroelectric and the paralectric phase of PbTiO3.
Keywords: Tip-Enhanced Raman Spectroscopy (TERS), FEM numerical method, field
enhancement, Surface plasmon polariton
[1] Norihiko Hayazawa, Yasushi Inouye, Zouheir Sekkat, Satoshi Kawata,’Metallized tip
amplification of near-field Raman scattering’, Optics communications, 183, 333-336,
(2000)
[2] A. Campion, and P. Kambhampati, 'Surface-enhanced Raman scattering', Chemical
Society Reviews, 27, 241-250, (1998).
Déposition de couches minces de TiO2:W,N par un procédé de co-pulvérisation-magnétron
réactive pour le développement de photoanodes actives sous lumière visible
N. Delegan,1 R. Pandiyan,1 A. Dirany,2 P. Drogui,2 and M. A. El Khakani 1,*
1
2
Institut National de la Recherche Scientifique, Centre-Énergie, Matériaux et Télécommunications,
1650 Blvd. Lionel-Boulet, Varennes, QC J3X-1S2, Canada
Institut National de la Recherche Scientifique, Centre-Eau, Terre et Environnement, 490 Rue de la
Couronne, QC G1K-9A9, Canada
*e-mail: [email protected]
Nous avons développé un procédé de co-pulvérisation-magnétron réactive pour la synthèse et le
dopage in situ au tungstène (W) et à l’azote (N) de couches minces de TiO2:W,N photoactives
dans le visible. Les dopants ont été incorporés sur une large plage de concentrations, notamment
de 0-3 at.% et 0-9 at.% pour le W et le N, respectivement. L’objectif du codopage W,N est
d’élaborer des couches minces photoactives dans le visible et passivées électroniquement. Les
analyses XPS nous ont permis de démontrer que les dopants s’incorporent principalement dans la
matrice de TiO2 de façon substitutionnelle, créant ainsi des niveaux énergétiques associés avec
l'absorption dans le visible. Par ailleurs, les analyses XRD ont démontré que le co-dopage
TiO2:W,N produit une certaine relaxation des contraintes internes de la structure anatase
présentes dans les couches minces de TiO2:W et TiO2:N. En effet, la présence du W comme codopant réduit la densité des lacunes d’oxygène (associées avec le monodopage de type TiO2:N),
et minimise ainsi le piégeage des photocharges. Les études par spectroscopie UV-Vis ont
confirmé une réduction significative de la bande interdite optique (Eg) de 3.2 eV jusqu’à ~2.3 eV
pour un dopage optimum du TiO2:N et du TiO2:W,N. Les mesures par UPS des fonctions de
travail et la localisation du niveau de Fermi (EF), du minimum de bande de conduction (CBM), et
du maximum de bande de valence (VBM), pour les différents cas de mono- et de co-dopage nous
ont permis de reconstruire les diagrammes de bandes, et de mieux comprendre les processus de
génération de photocharges dans ces couches de TiO2:W,N. Finalement, nous avons pu
confirmer l’efficacité de dégradation électro-photo-catalytique de l’atrazine (polluant réel), sous
illumination solaire, par nos photoanodes à base de couches de TiO2:W,N. En effet, les
photoanodes à base de TiO2:W,N dégradent ~98% de l’atrazine (60 ppb initiale) après à peine 37
min d’illumination, soit ~2 fois plus rapidement qu’avec le TiO2:N.
A “smart” material for “smart” applications, capitalizing on tunable phase
transition characteristics of vanadium dioxide thin films
N. Émond, A. Hendaoui and M. Chaker
Institut National de la Recherche Scientifique (INRS), University of Quebec, 1650, Blvd. LionelBoulet, Varennes, Quebec J3X 1S2, Canada
Vanadium dioxide (VO2) exhibits a reversible first-order semiconductor-to-metal transition
(SMT) at a temperature of TSMT ≈ 68 °C. This transition is accompanied by a structural transition
from a low-temperature (semiconductor) monoclinic phase to a high-temperature (metallic)
tetragonal phase and characterized by a 3 to 5 orders of magnitude change in VO2 electrical
resistivity and in significant changes in its reflectivity at both infrared (IR) and terahertz (THz)
frequencies. Moreover, the SMT characteristics of VO2, namely the transition temperature, the
sharpness of the transition, the amplitude of the properties modification and the related hysteresis
width, can be efficiently tailored through doping and through a proper control of the crystallinity,
the morphology and the stoichiometry of the films.
VO2 thin films with a wide variety of SMT characteristics have been synthesized on different
substrates using pulsed laser deposition, allowing to fully exploit this material for IR and THz
applications. It was demonstrated that the SMT characteristics of polycrystalline VO2 films in the
THz range can be efficiently tailored through a proper control of the oxygen pressure during
deposition, allowing for the development of THz “smart” devices such as sensor-type and
memories devices. The effect of W-doping on the SMT characteristics of VO2 films was also
studied and resulted in a large reduction of TSMT. Advantage of this reduction was first taken to
develop a new type of energy-efficient, light-weight, and high-performance variable-emittance
coatings based on WxV1-xO2 thin films (smart radiator device) that can passively control the
internal temperature of nano-satellites close to room temperature. The SMT properties of WxV1xO2 films were further exploited to achieve a WxV1-xO2 multilayer structure (MLS), with a
bottom-up gradient of tungsten content, which displays a combination of excellent electrical
characteristics and presents a great potential for the development of highly responsive sensing
layer in energy-efficient uncooled microbolometer.
Theoretical and Experimental Characterization of Optical Grating Coupler
F. Fesharaki 1, N. Hossain2, S. M. H. Kabir2, S. Vigne2, M. Chaker 2, and K. Wu1
1
2
Poly-Grames Research Center, École Polytechnique de Montréal, Montréal (Canada)
INRS – Centre Énergie, Matériaux, Télécommunications, Varennes (Canada)
Grating coupler, a region on top of or below a waveguide where there is a grating, is a kind of structure in
which guided-mode resonance takes place. Once designed accurately, resonance happens for specific
combinations of incident angles and light frequency and allows the grating to couple light into a guided
mode of the waveguide. In this work, a rigorous three-dimensional simulation of a grating coupler is
conducted for the first time. As a result, guided wave characteristics of an out-of-plane grating coupler are
studied in detail and leakage characteristics, radiation pattern and the coupling efficiency are evaluated.
Silicon on Insulator (SOI) wafer- with a 260 nm silicon layer and 2 µm buried oxide (BOX) - was utilized
in our design and fabrication. Two different periods were considered, resulting in two slightly different
coupling angles. Test structures with grating couplers and tapered strip waveguides were fabricated.
Electron Beam Lithography (EBL) (Vistec VB6 UHR-EWF) and Inductively Coupled Plasma – Reactive
Ion Etching (ICP-RIE) (Oxford PlasmaLab System100) were used for the fabrication of our device based
on the SOI substrate. Because the fiber couplers require a different etch depth than the other optical
structures, they have to be fabricated in a separate process step. Two sets of alignment marks for this twolevel microfabrication steps were then first patterned by EBL in positive electron beam resist ZEP520a
and transferred into the top Si layer using a SF6/C4F8 ICP etch chemistry. Optical end-point detection
system stopped the etching process when the BOX is reached, to maximize the contrast during subsequent
EBL exposures. The sample was then cleaned, same positive resist was spin coated and the grating
couplers were patterned by EBL using a first set of alignment marks. The fabricated samples were
characterized by various coupling angles over 100 nm wavelength spectrum. The fabricated grating
couplers show a coupling efficiency higher than 35% over 50 nm wavelength bandwidth. The optimized
coupling angles are 7.5° and 12° for the 580 nm and 600 nm grating periods respectively, in agreement
with the full-wave simulation values of 7° and 13°. The corresponding coupling efficiencies were 42%
and 38 %. This excellent agreement between theory, simulation and experiment fully validates the design
and fabrication method.
1/1
Strong magnetization of laser-produced plasmas as a new tool for investigating
astrophysics and fusion physics
J. Fuchs
LULI, École Polytechnique, CNRS, CEA, UPMC, F-91128 Palaiseau, France.
Coupling high-power lasers and high-strength B-fields helps gaining unique insight and understanding
of a variety of phenomena of crucial importance for astrophysics and Inertial Confinement Fusion. We
have shown that such platform could be used to mimic the expansion of a young star isotropic disk
wind threaded by a co-axial poloidal magnetic field. It reveals that long-range collimated jets can
indeed by result from such system, complementing toroidal B-fields that help shape the initial matter
from the star into a jet. The same system can then be used to study the dynamics of the accretion of
magnetized plasma columns onto star surfaces and help decipher the underlying physics, or also the
issue of particle energization in astrophysical plasmas. But it can also serve as a test-bed to evaluate the
impact of B-fields onto ICF plasmas, a topical subject since it has been recently shown that such
magnetization could help increase the temperature of ICF cores, opening a path for potential increase of
ICF experiments energy gain.
IMPACT OF HEXAMETHYLDISILOXANE INJECTION ON THE ELECTRON TEMPERATURE AND
EXCITATION IN LOW-PRESSURE RF PLASMAS WITH CYCLIC FORMATION & DISPEARRANCE OF
DUST
Vincent Garofano1, Luc Stafford1, Bernard Despax2, Richard Clergeraux2 and Kremena Makasheva2
1
Université de Montréal, Montréal, Québec H3C 3J7, Canada
2
LAPLACE (Laboratoire Plasma et Conversion d’Energie), Université de Toulouse, CNRS, UPS, INPT, 118 route de
Narbonne, F-31062 Toulouse 09, France
Optical emission spectroscopy was used to analyze the very-low-frequency cyclic evolution of the electron energy and
density caused by repetitive formation and loss of dust nanoparticles in argon plasmas with pulsed injection of
hexamethyldisiloxane (HMDSO, [CH3]6Si2O). Optical emission spectra were recorded in the dust cloud. A first
wavelength interval containing close Ar emission lines around 600 nm emanating from Ar excited states close to the
ionization level was used to construct a Boltzmann diagram. On the second hand, by introducing a trace of rare gases
(20% Xe, 20% Kr, 20% Ar, and 40% Ne) in the nominally pure Ar plasma, trace-rare gases optical emission spectroscopy
measurements could be performed for wavelengths between 750 and 900 nm. The measured emission intensities of Ar,
Kr, and Xe were then compared to the predictions of a collisional-radiate model, with the electron temperature as the only
adjustable parameter. These two methods gave temperatures characterizing the high and low energy part of the electron
population. Relative electron densities were also estimated from relative line emission intensities. Both temperatures rose
when dust occupation increases, and then decreased when dust is lost. The opposite trend was observed for the electron
density [1]. Such cyclic behaviors of the electron energy and electron density in HMDSO-containing plasmas is in good
agreement with the evolution processes in dusty plasmas, in which the formation of negative ions followed by electron
attachment on nanoparticle's surfaces are critical phenomena driving dust growth. Evolution of the very-low frequency
describing this cyclic behavior with the operating parameters is also investigated. While the frequency unsurprisingly
increases with total pressure and HMDSO flow, it decreases with power, a feature that has yet to be understood.
[1]
V. Garofano, L. Stafford, B. Despax, R. Clergereaux, and K. Makasheva, “Cyclic evolution of the electron
temperature and density in dusty low-pressure radio frequency plasmas with pulsed injection of
hexamethyldisiloxane,” Appl. Phys. Lett., vol. 107, no. 183104, pp. 0–5, 2015.
NumericalModelingofNanodustyPlasmas
StevenL.Girshick
DepartmentofMechanicalEngineering,UniversityofMinnesota
Minneapolis,MN,USA
Abstract
Nonthermalplasmasinwhichnanoparticlesnucleateandgrow—“nanodusty”
plasmas—presentarichvarietyofphysicalandchemicalphenomena,manyofwhichare
poorlyunderstoodinadditiontobeingcoupledtoeachother.Theabilitytopredictthe
spatiotemporalevolutionofsuchplasmaspresentsanenormouschallengetonumerical
modeling.Inthistalkanoverviewwillbegivenofthestatusofsuchmodeling,withafocus
onradiofrequencysilane-containingplasmasthatareusedforsynthesisofsilicon
nanoparticles.Phenomenaconsideredincludeparticlenucleation,growthbyphysicalor
chemicalvapordepositiononparticlesurfaces,coagulation,particlecharging,nanoparticle
transportbyneutraldrag,electrostaticforces,iondrag,Browniandiffusion,
thermophoresisandgravity,andtheself-consistentcouplingoftheaerosolphasetothe
plasmabehavior.Modelsofdifferentdegreesofcomplexitywillbediscussed,aswellasthe
computationalchallenges.
Étude de la physico-chimie et de l'architecture de revêtements
d'hydroxyapatite élaborés par projection de suspension dans un plasma
inductif
Frederic Faivre1-2, François Gitzhofer1, Ghislaine Bertrand2, David Grossin2, Cédric Charvillat2,
Olivier Marsan2
1. Université de Sherbrooke, Laboratoire de génie des plasmas, Sherbrooke, Qc, Canada
2. CIRIMAT, Université de Toulouse, CNRS, INPT, UPS, Toulouse, France
Mots Clés : hydroxyapatite, plasma RF, suspension, revêtement, Rietveld, Raman.
RESUME
Les revêtements d'hydroxyapatite (HA), Ca10(PO4)6(OH)2, réalisés par projection plasma
atmosphérique conventionnelle (APS), sont largement utilisés pour améliorer l’intégration des prothèses
osseuses Leurs excellentes biocompatibilité et ostéconductivité ont un effet positif sur la repousse osseuse
au début de l'implantation. Cependant, la stabilité à long terme est toujours controversée. En effet, la
poudre projetée se décompose dans le plasma et forme un dépôt avec une forte hétérogénéité chimique et
structurale (présence de phase amorphe à l'interface avec le substrat). Des caractéristiques telles que la
composition chimique, la cristallinité, les phases cristallographiques et leur répartition dans l’épaisseur
mais surtout aux interfaces os/revêtement et revêtement/titane ont donc été identifiées comme ayant une
forte influence sur la durée de vie de ce type de revêtement.
La projection de suspension dans un plasma RF est un procédé assez versatile pour permettre de
développer un nouveau revêtement aux propriétés, qui influencent la durée de vie de l’implant, maîtrisées.
En outre, ce procédé permet de s’affranchir de l'étape de production d'une poudre grâce à la formulation
d'une suspension directement projetable. L'objectif de cette étude est de mesurer l'influence des paramètres
opératoires (pression, puissance, distance de projection) sur les propriétés physico-chimiques, structurales
et architecturales du dépôt. Le challenge de cette étude est de réaliser une caractérisation assez précise
pour identifier, quantifier et localiser les différentes phases.
Les paramètres opératoires ont un fort impact sur les caractéristiques du revêtement ce qui nous
permet de les contrôler. Ainsi, nous avons réussi à obtenir des dépôts composés d'une phase majoritaire
d'HA modulable de 40 à 90% en masse et le reste étant composé d'un mélange non exhaustif de tri
calcium de phosphate (α ou β-TCP), d'oxyde de calcium (CaO) et de tétra calcium de phosphate (TTCP).
De plus, les tailles des cristallites d’HA sont également contrôlables tout en restant nanométrique (30 à 60
nm) comme ont pu le prouver les caractérisations par diffraction des rayons X. Une phase d'oxyapatite
(OA) ainsi que la présence de phosphate de calcium amorphe (ACP) ont été mises en évidence par
spectroscopies infrarouge et Raman. La cartographie d’une coupe transversale d’un dépôt par
spectroscopie Raman a révélé une décroissance de la contribution des phases amorphe et oxyapatitique
dans l’épaisseur vers le substrat.
Plasma-Quebec 2016
1-2 June 2016, Montreal
Re-sputtering effect in on-axis RF-magnetron sputtered of SrTiO3 thin films from single
stoichiometric target
Azza Hadj Youssef1, R. Nouar2, A. Sakissian2, R.Thomas1 and A. Ruediger1
1
Nanoelectronics-Nanophotonics, 2 Plasmionique Inc
Centre Énergie Matériaux et Télécommunications, INRS, 1650 Lionel-Boulet, Varennes, Québec, J3X1S2,
Canada
Abstract
SrTiO3 in the perovskite structure is a very attractive material for application in microelectronics not
only because of its high charge storage capacity and good insulating properties but also as a wide-gap
semiconductor with a band gap of ~ 3.2 eV. It has also attracted interest in the world of oxide
electronics, in particular as a substrate for heteroepitaxy. In this work strontium titanate thin film
deposition was performed by an on-axis RF-magnetron sputtering technique. The thin film growth
process was systematically studied to achieve stoichiometrically grown films. The growth of SrTiO3
thin film showed undesired substrate etching due to the production of negative oxygen ions. The onaxis geometry used in the present study accelerated re-sputtering. At high RF-power, surface etching
has been observed at the center of the substrate and the diameter of this etched circle was similar to the
diameter of the target. However, deposition was possible in regions outside this etching zone. To
achieve stoichiometric SrTiO3 thin film deposition at the axis-center, deposition pressure was adjusted
to limit the effect of these negative ions to a minimum Polycrystalline growth of SrTiO3 thin films on
platinized silicon substrates was optimized systematically and further extended to the epitaxial
deposition on single crystal MgO substrates. The stoichiometry and surface morphology were
investigated by X-ray photoelectron spectrometry (XPS) and atomic force microscopy (AFM),
respectively. Structural investigations were done by Raman spectroscopy and X-ray diffraction (XRD).
New multiferroic thin films based on tetragonal tungsten bronze
structure Ba2LnFeNb4O15 (Ln = Eu and Sm) deposited by pulsed laser
deposition
T. Hajlaoui1, C. Harnagea1, and A. Pignolet1
1
Institut National de la Recherche Scientifique – Centre Énergie, Matériaux, Télécommunications,
1650 Boulevard Lionel-Boulet, Varennes, Québec, J3X 1S2, Canada
Contact author: [email protected] (Thameur Hajlaoui)
The study of Ba2LnFeNb4O15 (TTB-Ln) bulk ceramics revealed that they have a
tetragonal tungsten bronze crystal structure, are ferroelectric and that a magnetic phase of
barium hexaferrite BaFe12O19 (BaFO) spontaneously forms within the TTB-Ln phase
during the ceramic processing, resulting in a novel multiferroic composite material at
room temperature.
Our goal is to investigate new room-temperature multiferroic thin films grown by
pulsed laser deposition (PLD), namely thin films of the spontaneously forming composite
BaFO/TTB-Ln (Ln = Eu and Sm). c-oriented thin films of TTB-Ln have been
successfully grown on Nb doped SrTiO3(100) substrates by PLD. In specific and
optimized growth conditions, the structural study of the BaFO/TTB-Ln thin films shows
an epitaxial growth perpendicularly to the substrate plan and parallel to the c-axis of
tetragonal crystal structure. Further structural analysis reveals two kinds of azimuthal
orientation of the c-axis oriented grains of TTB-Ln onto the cubic substrate, with the a
and b axes of TTB-Ln aligned at 18° with respect to the a-axis of the cubic substrate.
Ferroelectric macroscopic hysteresis loops demonstrate the existence of a spontaneous
polarization at room temperature. An enhancement of the ferroelectricity due to the
epitaxial growth has been evidenced. To further study the ferroelectricity in TTB-Ln thin
films, local electromechanical properties were studied using piezoelectric force
microscopy. These experiments allowed determining the piezoelectric coefficient and
confirming that the ferroelectric nature of the studied thin films is conserved down to the
nanoscale. Finally, the magnetic properties of BaFO/TTB-Ln thin films were studied
which reveals that the PLD grown BaFO/TTB-Ln composite films exhibit a
ferromagnetic behavior at room temperature, confirming their multiferroic nature at room
temperature.
Photovoltaic Properties of Multiferroic Bi2FeCrO6 Based p-i-n Heterojunctions with
p-Type and n-Type Oxides
Wei Huang1, Riad Nechache2, Catalin Harnagea1, Mohamed Chaker1 and Federico
Rosei1,3
1
INRS -Centre Énergie, Matériaux et Télécommunications, 1650, Boulevard Lionel-Boulet, Varennes,
Québec J3X 1S2, Canada.
2
École de Technologie Supérieure, 1100 Rue Notre-Dame Ouest, Montréal, Québec H3C 1K3, Canada.
3
Center for Self-Assembled Chemical Structures, McGill University, 801 Sherbrooke Street West Montreal,
Québec H3A 2K6, Canada
Multiferroic materials are increasingly being studied for solar energy conversion
technologies due to their efficient ferroelectric polarization-driven carrier separation and
above-bandgap generated photovoltages. Multiferroics possess a magnetic order
parameter besides the ferroelectric one and the electron–electron interaction governing
the magnetic ordering induced a smaller gap than the other ferroelectric materials,
leading to higher photovoltaic (PV) efficiencies. Recently, our group reported the power
conversion efficiency of 8.1% for Bi2FeCrO6 (BFCO) thin-film solar cells with tunable
bandgap of multiferroic oxides by engineering the cationic Fe/Cr ordering. However, the
low band-gap BFCO with high cationic Fe/Cr ordering showed very weak ferroelectric
properties, resulting in reduction of separation of photogenerated charge carriers and
probably increase of recombination of electrons and holes, thus hindered the effective
transport of photogenerated carriers. To enhance the internal electric field in highly
ordered, low band-gap BFCO, a sandwich structure of p-i-n heterojunctions is designed.
In this p-i-n junction, the multiferroic thin film acting as intrinsic absorber is sandwiched
between p- and n-type semiconductor oxides as hole- and electron- collecting layer,
respectively, so that the depletion regions at the p-i and i-n are added up and an internal
field is formed across the entire layer of multiferroic material.
In this work, we have used highly ordered BFCO as an absorber. Inorganic oxides, such
as In-doped SrTiO3, NiO or MoO3 as a p-type hole-collecting layer and Nb-doped SrTiO3
or Al-doped ZnO as an n-type electron-collecting layer, have been used along with the
multiferroics to form a p-i-n heterojunctions PV device.
Keywords: photovoltaic, multiferroic, perovskite, heterojunction, power conversion
efficiency.
Presenting author’s email: [email protected]
Polarisation nucléaire d'hélium 3 par pompage optique et échange de métastabilité
Rhanem Jbilat*, François Vidal*
* Institut National de la Recherche Scientifique
L'hélium 3 (3He) est un isotope rare de l'hélium dont le noyau possède deux protons et un seul neutron.
Du fait de son nombre impair de nucléons, le noyau d'3He possède un spin non nul et un gaz d’3He est
dit polarisé lorsqu’une grande proportion des spins nucléaires est orientée dans la même direction.
L'3He polarisé a des applications intéressantes, notamment dans le domaine médical, industriel ou de
recherche. Il est employé par exemple dans de nouvelles techniques d'imagerie par résonance
magnétique nucléaire (IRMN).
L'3He peut être polarisé notamment par Pompage Optique et Échange de Métastabilité (POEM), qui
consiste en un transfert de moment angulaire d'un laser polarisé circulairement du niveau métastable
23S1 vers le niveau 23P, suivi d'un échange collisionnel dit de métastabilité entre le niveau 23S1 et le
niveau fondamental de l’hélium.
Dans le cadre de notre projet de développement d’un modèle collisionnel et radiatif du plasma
d’hélium, je me concentre sur la modélisation du POEM. Le modèle de POEM que je considère traite
la dynamique temporelle des populations des différents sous niveaux hyperfins du niveau métastable
23S1 et du niveau 23P, en plus de celle du taux de polarisation. Il tient compte de différents
phénomènes, notamment le pompage optique, les émissions stimulées et spontanées, l'échange de
métastabilité et l’établissement de la polarisation, et se ramène à un système d'équations différentielles
ordinaires couplées.
Pour résoudre ce système, j'utilise des méthodes numériques que je programme avec le langage
Fortran. Les programmes demandent une bonne capacité de calcul en raison des échelles de temps très
différentes présentes dans le POEM (entre 10-8 s pour le pompage optique et 10 s pour l'établissement
de la polarisation du gaz). Mes résultats montrent la possibilité d'obtenir un taux de polarisation de
l'ordre 70%. Aussi, l'étude paramétrique permet d'analyser le rôle des différents paramètres intervenant
dans le modèle. Ce modèle de POEM sera ultérieurement intégré dans notre modèle collisionnel et
radiatif complet du plasma d’hélium.
Cela fera le sujet de ma présentation d’aujourd'hui. Bienvenue à tous!
Effet de l’eau et de la chaleur sur la stabilité de couches minces organiques déposées par plasma
pour la fonctionnalisation des NTCs multi-parois
L. Jorge, P.-L. Girard-Lauriault et S. Coulombe
Laboratoire des procédés plasmas (PPL), Département de génie chimique,
Université McGill, Montréal (QC), Canada
L’adsorption de surfactants et de polymères sur la surface des nanotubes de carbone (NTCs) est
une technique fréquemment utilisée pour la préparation de nanofluides (NFs) stables. Selon les
groupements fonctionnels présents sur ces molécules ajoutées, il est ensuite possible d’y attacher des
molécules plus complexes ou des nanoparticules (NPs) afin d’utiliser les NFs pour la détection de gaz
ou des applications biologiques.
Nous développons des NFs à base de NTCs multi-parois fonctionnalisés par plasma radiofréquentiel (RF, 13.56 MHz) à basse pression. Lors de l’exposition au plasma opérant à 35 W sous une
atmosphère d’ammoniac, NH3, et d’éthylène, C2H4, les NTCs multi-parois sont recouverts d’une
couche mince organique contenant environ 22 at% d’azote dont une partie sous forme d’amines
primaires, -NH2. En remplaçant NH3 par du dioxyde de carbone, CO2, la couche déposée contient 22
at% d’oxygène et des groupes carboxyles, -COOH, tel qu’observé par spectroscopie de photoélectrons
induits par rayons X. Des analyses thermogravimétriques sous atmosphère d’azote indiquent que ces
couches organiques sont stables jusqu’à 150 oC, mais perdent les deux tiers de leur masse initiale
lorsque chauffées à 550 oC. Ces couches organiques déposées par plasma peuvent aussi être exposées à
l’eau, où elles sont alors partiellement oxydées, sans que cela affecte leur capacité à stabiliser les NTCs
dans le NF. Dans l’eau, les groupes amines seront chargés positivement, formant –NH3+, alors que les
groupes carboxyles seront chargés négativement, -COO-, ce qui permet de contrôler l’ajout d’autres
nanoparticules sur les NTCs. Cela a été testé en observant la déposition d’une couche uniforme de NPs
d’or chargées négativement sur les NTCs recouverts de la couche azotée mais aucune NP sur les NTCs
fonctionnalisés par CO2.
Pulsed Laser Deposition of CaxBa1-xNb2O6 thin film on GGG substrate
S. M. H. Kabir1, N. Hossain1, F. Fesharaki2, K. Wu2, J. Margot3 and M. Chaker1
1
Poly-Grames Research Center, École Polytechnique de Montréal, Montréal (Canada)
3
Département de Physique, Université de Montréal, Montréal (Canada)
2
Calcium-barium niobate (CaxBa1-xNb2O6, CBN) thin film material has received great attention for the
development of integrated optical components such as waveguides, Electro-Optic (EO) modulator,
grating coupler, etc., owing to its promising electrical and optical properties. Previously, CBN thin film
was synthesized on different substrates such as MgO, Nb:SrTiO3, as well as on Si using MgO as buffer
layer. All those substrates are highly lattice mismatch to CBN and hence CBN thin film on those
substrates were grown as domain matching technique which eventually limit not only the thin film
material quality but also the device performance. To overcome these limitations, we have synthesized
CBN thin film on closely lattice matched Gadolinium Gallium Garnet (GGG, Gd3Ga5O12) substrate by
Pulsed Laser Deposition (PLD) technique.
In our PLD experiment, a KrF excimer laser (248 nm, 16 ns pulse) was focused onto a commercially
bought CBN-28 target. During deposition both the target and substrate were kept rotating. The laser
fluency on the target was 2 J/cm2 with spot size of 0.07 cm2. The laser repetition rate and the targetsubstrate distance was 20 Hz, and 65 mm, respectively. At first, CBN deposition was carried out under
various substrate temperature 650, 700, 750, and 800°C while keeping all other parameters constant. Xray diffraction (XRD) measurement shows the optimal growth temperature is 750°C where the most
intensely (001) peak is found. Also, no secondary phases are detected in θ-2θ scan. Keeping this optimal
temperature and other parameters constant, effect of oxygen partial pressure on CBN thin growth was also
observed. For this, CBN deposition was carried out under various oxygen pressures ranging from 1 to 200
mTorr. Subsequently, the films were cooled down to bellow 100°C at cooling rate of 20°C per minute
before taking out from vacuum chamber. Best CBN thin film was found at oxygen partial pressure of 50
mTorr. At this pressure, highly oriented in (00l) direction CBN thin film is found. At high ambient gas
pressure the kinetic energy of the ablated species reduced due to the multiple collisions occurring with
oxygen atoms or molecules. As a result, the impinging species do not have enough energy to migrate on
the surface and they are mostly deposited without any particular rearrangement. Therefore, under high
oxygen partial surface roughness increased significantly as well as porous thin film is grown.
Furthermore, chemical composition of the deposited thin film was measured by X-ray photoelectron
spectroscopy (XPS) which verify the stoichiometric transfer.
1/1
Bi2FeCrO6 deposition by hydrothermal synthesis and radio-frequency magnetron
sputtering
G. Kolhatkar1, F. Ambriz Vargas1, A. Sarkissian2, R. Thomas1, A. Ruediger1
Institut National de la Recherche Scientifique – Centre Énergie, Matériaux,
Télécommunications, 1650 Boulevard Lionel-Boulet, Varennes, Québec, J3X 1S2, Canada
2
Plasmionique Inc., 1650 Lionel-Boulet, Varennes, Québec, J3X1S2, Canada
1
Contact author: [email protected]
Abstract
Multiferroics materials combine both ferroelectric/ferrielectric/antiferroelectric and
ferromagnetic/ferrimagnetic/antiferromagnetic and/or ferroelastic properties at room temperature,
making them suitable for non-volatile random access memories [1]. Amongst them, doubleperovskite Bi2FeCrO6 has been attracting a lot of attention. The double-perovskite nature of the
crystal structure enhances the ferroelectric and ferromagnetic properties of the material.
Furthermore, Bi2FeCrO6 displays interesting photovoltaic properties [2].
In this work, we study the deposition
of Bi2FeCrO6 films. While most research
previously reported used pulsed laser
deposition or chemical solution deposition,
our work focuses on two different, techniques:
radio-frequency (RF) magnetron sputtering
(°)
+10 V
and
microwave-assisted
hydrothermal
synthesis. RF magnetron sputtering enables a
-9 V
higher film uniformity over a larger area,
making it more favorable for the industry,
while hydrothermal synthesis is highly
0
inexpensive and does not require any
Figure 1 : 2 μm × 2 μm phase mapping of sophisticated
equipment.
Moreover,
Bi2FeCrO6 on (111) STO deposited by hydrothermal synthesis is performed at low
hydrothermal synthesis.
temperature with a good stoichiometry
control. The depositions were performed on
(111) oriented strontium titanate (STO) substrates. For hydrothermal synthesis, bismuth nitrate
(Bi(NO3)3), iron nitrate (Fe(NO3)3) and chromium nitrate (Cr(NO3)3) were used as precursors. A
potassium hydroxide solution was used as a mineralizer. A commercially available 50%-50%
BiFeO3-BiCrO3 target was utilized for the sputter deposition of double perovskite Bi2FeCrO6 films.
The effects of deposition time, temperature and pressure as well as concentration on the Bi2FeCrO6
films are studied. Using hydrothermal synthesis, we demonstrate polarization switching, as
illustrated in figure 1, attesting to the potential of this deposition technique. This comparative study
will provide us with an alternative, cheap method to produce Bi2FeCrO6 films for multifunctional
applications.
180
[1]
[2]
R. Ramesh, N. A. Spaldin, Nat. Mater. 2007, 6, 21.
R. Nechache, C. Harnagea, S. Licoccia, E. Traversa, A. Ruediger, A. Pignolet, F. Rosei,
Appl. Phys. Lett. 2011, 98, 202902.
Superstructures dans le BiFeO3
J. Laverdière1, P. Lafontaine-Martel1, F. Rosei1, M. Chaker1
1
Il est bien connu que les matériaux cristallins sont fréquemment étudiés par
diverses techniques de diffraction (rayons X, neutron, électrons, etc.) en raison de
leur nature périodique. En diffraction de rayons X, la périodicité d'un réseau
cristallin, i.e. la taille de sa cellule unité, est directement reliée à la position angulaire
des ordres de diffraction des plans cristallins. Par exemple, le patron de diffraction
de la solution solide de BiFe0.5Cr0.5O3 devrait être très similaire à celui du BiFeO3.
Par contre, le Bi2FeCrO6, dans lequel les métaux de transition sont parfaitement
ordonnés, possède une cellule unité deux fois plus grande, i.e. une fréquence
spatiale deux fois plus petite. Son patron de diffraction présente donc des réflexions
supplémentaires à des angles plus faibles, souvent appelées réflexions de
superstructure. C'est pourquoi la diffraction de rayons X a été utilisé pour
caractériser l'ordre cationique des matériaux dit pérovskites doubles [1–3].
Or, contre toute attente, les résultats de cet exposé révèleront que la diffraction de
rayons X du BiFeO3 présente également des réflexions de superstructures. En
utilisant différentes orientations de substrats de SrTiO3, nos comparerons l'effet des
contraintes sur la structure. Nous montrerons qu'une distorsion monoclinique
imposée par une contrainte compressive dans le plan (001) cause l'apparition d'une
modulation du réseau dans toutes les directions <111>. Des hypothèses sur le
mécanisme de relaxation seront proposées pour expliquer cette modulation.
L'impact de l'existence d'une superstructure dans le BiFeO3 et la possibilité qu'elle
soit impliquée pour relaxer des déficiences chimiques sera discuté.
[1]
[2]
[3]
B.-K. Kim and S.-Bae Cha, Mater. Res. Bull. 32, 743–747 (1997).
J. Andreasson et al., , Phys. Rev. B 80, 075103 (2009)
R. Nechache et al., Nat. Photonics 9, 61–67 (2014)
1
2016-04-12
Presentation at Plasma-Québec
Title: Self-assembled and programmable electronic networks of VO2 nanodevices
Authors: Dominic Lepage*, Jérémie Chaillou, Mohamed Chaker
Affiliations: INRS
Abstract:
Materials exhibiting collective carrier dynamics can enable entirely new applications in solid state
physics and lead to devices with drastically innovative functionalities. A canonical example of such
correlated system is vanadium dioxide (VO2), which undergoes a semiconductor to metal phase transition
via the application of heat, electricity or light-pumping. This presentation will highlight the nanometerscale functioning of a simple VO2 device consisting of two metal contacts on a polycrystalline VO2 layer
deposited by Pulsed Laser Deposition (PLD).
For layer thicknesses under 150nm, the resulting system is a self-assembled network of nanometric
VO2 grains in a hexagonal compact configuration. For the 8x8µm samples presented, it is the interplay of
6400 connected grains that will result in the macroscopic observations. The initial state of the system is
described in a probabilistic manner which is function of the substrate temperature. Furthermore, between
any two grains, an innate barrier can arise from the local charge trapping by local gap states. As an
electrical power is applied to the device, each individual grains can either be in the semiconducting or
metallic state, depending on the local electron flux passing through them. Electrically conductive filaments
and specific pathways can thus be grown within the layer as a function of local initial conditions, sustained
via temperature or electrical current, and then reset. When the grains’ potentials are not externally fixed
and the voltages free to change, the device can also present a negative differential resistance as the
fraction of grains switching from semiconductor to metal are increasing. Simultaneously, charges are
accumulating within the device, especially at metal-insulator interfaces forming local Schottky junctions
which grow in a branching fractal manner if unguided. This leads to self-oscillations, where the charges at
the grains interface accumulates and are spontaneously discharged, with frequencies as high as 9MHz.
In this talk, we will show the measurements of current vs. voltage vs. temperature and of voltage vs.
time that are used to deduce the physical properties of those grain junctions in all possible configurations.
The current flowing through the network is then predicted by a self-consistent time-dependent electronic
network model. Time-varying maps of the local current densities will illustrate how such simple VO2 layers
can form an electronic network of nanodevices capable of complex behaviors. The presentation will end
on an open talk on specific applications of such systems and potential methods for the large scale
fabrication of phase transition metal oxides devices.
1|1
Anatase-phase titanium dioxide films deposited at
atmospheric pressure using dielectric barrier discharge (DBD)
Zineb Matouk1, Rocio Rincon1, Paul Brunet1,2, Françoise Massines2, Mohamed
Chaker1
1
INRS, Centre Énergie Matériaux et Télécommunications, INRS, 1650 Lionel-Boulet, Varennes,
Québec, J3X1S2, Canada
2
Laboratoire PROcédés Matériaux et Energie Solaire, UPR 8521, Tecnosud, 66100 Perpignan, France
Titanium dioxide both bulk material and nanoparticules (TiO2 NPs) have been widely
investigated because of their potential applications such as photochemistry or photocatalysis
[1]. In this work, atmospheric-pressure Dielectric Barrier Discharge (AP-DBD) N2/N2O plasma
was used to deposit TiO2 NPs. TiO2 NPs (20-30 nm in diameter and 20% rutile, 80% anatase)
were dissolved in isopropanol and introduced into the plasma for the synthesis of the films. The
morphology, the composition and crystalline structure of the deposited TiO2 films were
investigated by scanning electron microscopy, X-ray photoelectron spectroscopy and X-ray
diffraction, respectively. The results showed that the microporous films prepared by the DBD
plasma deposition were rich enough in Ti with ~ 15%. Furthermore, the films were
characterized as anatase TiO2 structures with (101) preferential orientation. For the first time
with a plasma-based methodology, it is demonstrated that it is possible to obtain TiO2 anatase
film without neither post treatment nor extra heating. Low temperature AP- DBD plasma has
been demonstrated to be a fast and industrial-scalable method for the synthesis of TiO2 films.
[1] R. Daghrir et al. Ind. Eng. Chem.Res.10 (2013) 52.
*
[email protected]
Formation des stents biodégradables par technique de dépôt physique en phase vapeur (PVD) par arc
électrique
N. Y. Mendoza-González1, J.-L. Meunier1, T. Azar2 and R. Cecere3
1
Plasma Processing Laboratory (PPL), Chemical Engineering Department, McGill University, Montreal H3A 0C5
2
Mechanical Engineering Department, McGill University, Montreal H3A 0C5
3
Faculty of Medicine, Department of Surgery, Division of Cardiac Surgery, McGill University, Royal Victoria
Hospital, Montreal, H4A 3J1
Ce travail présente des résultats préliminaires sur la voie de la création d'un nouveau stent métallique
biodégradable à base de fer (Fe) et d’acier inoxydable (SS). Ces deux éléments, en tant que couple
galvanique, fournissent des particules anodiques et cathodiques qui sont corrosives lorsqu’elles sont
immergées dans un environnement salin (sang) conduisant ainsi à la biorésorption du stent.
La construction du système composé de nanoparticules inter-mélangés de Fe et SS a été fait à l’aide
d’un système industriel de dépôt PVD par arc (PVD Ionbond 350). Dans cette technique, des cibles
métalliques de Fe et SS sont évaporées dans des conditions de vide et de polarisation contrôlées pour
déposer un composite de nanoparticules inter-mélangés sur un substrat. La pression de dépôt est
typiquement 1.2x10-2 Torr. Le faisceau d'ions à plasma a été généré par une décharge à arc à courant
continu de 50 A avec 80 sccm d'argon comme gaz d'arrière-plan. Pendant toutes les étapes, le carrousel
planétaire à l'intérieur de la chambre est mis en rotation à 2 tours par minute pour garantir que toutes
les surfaces du substrat traversent les zones de plasma, conduisant à une épaisseur de revêtement
uniforme.
Des essais préliminaires ont été effectués en revêtant des nanoparticules métalliques sur des substrats
en céramique avec 1) Fe, 2) SS et 3) le rapport de Fe-SS de 1:1. Une moyenne d'épaisseur de revêtement
de 200 nm a été mesurée avec un profilomètre Dektak après un procédé de recouvrement de 25
minutes. La morphologie des échantillons a été observée avec microscope optique et microscope
électronique à balayage (SEM). Les images SEM montrent en détail une structure formée par des
particules inter-mélangées de SS et Fe à taille nanométrique et très peu de particules de taille
micrométrique. Afin d'observer le processus de biodégradation, les échantillons ont été immergés dans
une solution saline pendant 5 jours. L'observation visuelle et la mesure de la perte de poids ont montré
une dégradation plus élevée sur les échantillons de rapport Fe-SS 1:1.
Cette étude préliminaire montre que la technique PVD / plasma est une voie possible pour la
construction d’une nanostructure de particules de Fe-SS inter-mélangés. Un ratio adéquat de Fe et SS
peut former un couple galvanique et ouvrant la voie pour les stents biodégradables. Le travail futur
consiste à faire des tests de différents rapports de mélanges de Fe et SS ainsi que des tests
électrochimiques / mécaniques des structures résultantes.
La projection par plasma : Applications et développements récents
Christian Moreau
Chaire de recherche du Canada en ingénierie de surface et projection thermique
Université Concordia
Montréal (Québec), Canada
La projection par plasma est un procédé de déposition de revêtements utilisé industriellement pour
protéger des composantes contre l’usure, la corrosion, les hautes températures, etc. Dans ce procédé,
un arc électrique est utilisé pour former un jet de plasma dont la température excède 10,000K. Le
matériau de dépôt est introduit dans ce jet de plasma thermique sous forme de poudres fines. Celles-ci
sont fondues, accélérées à haute vitesse par le jet de plasma et projetées sur le substrat où elles se
solidifient rapidement formant un revêtement protecteur. Ce procédé de déposition est polyvalent, car
il permet de réaliser des revêtements céramiques, métalliques, polymères ou composites sur des
composantes de dimensions variant de quelques millimètres à plusieurs mètres.
Dans cette présentation, un survol de la technologie sera présenté avec une revue des principales
applications industrielles dans les secteurs de l’aérospatiale, l’automobile, l’énergie, etc. Nous
aborderons aussi les technologies émergentes de projection par plasma de suspensions et de solutions
qui sont l’objet de travaux de recherche importants, car ils permettent de réaliser des dépôts
nanostructurés à des taux de l’ordre du kilogramme à l’heure.
Energetics of Reactions in a Dielectric Barrier Discharge with Argon
Carrier Gas: Esters
Bernard Nisol1, Sean Watson1, Sophie Lerouge2, Michael R. Wertheimer1*
1
Groupe des Couches Minces (GCM) and Department of Engineering Physics, Polytechnique
Montréal, Box 6079, Station Centre-Ville, Montreal QC, H3C 3A7, Canada
2
Research Centre, Centre Hospitalier de l’Université de Montréal (CRCHUM), and Department
of Mechanical Engineering, École de technologie supérieure (ÉTS), Montréal (Qc), Canada
*Corresponding author; e-mail: [email protected]
A large research reactor for dielectric barrier discharge (DBD) experiments at
atmospheric pressure (AP) has been used with argon (Ar) carrier gas under constant
plasma conditions (𝑓𝑓 = 20 kHz, 𝑉𝑉a (𝑓𝑓) = 8 kVp-p = 2.8 kVrms). Five esters, acrylates with
differing number of unsaturations were used as “monomers”; monomer flows, 𝐹𝐹d , were at
‰ concentrations in the F = 10 standard liters per minute (slm) of argon. We earlier
perfected and reported a method for measuring 𝐸𝐸g , the energy dissipated per cycle of the
applied a.c. voltage, and ∆𝐸𝐸g , the energy difference with and without monomer in the Ar
flow. The latter, combined with 𝐹𝐹d , enable calculation of 𝐸𝐸m , the average energy
absorbed from the plasma per monomer molecule. Plots of 𝐸𝐸m versus 𝐹𝐹d and 1/𝐹𝐹d yield
much valuable information, for example about the role of C=C and C≡C bonds in
fragmentation and polymerization reactions. Fourier-transform infrared (FTIR)
spectroscopy, Spectroscopic Ellipsometry (SE) and Scanning Electron Microscopy (FEGSEM) further enhance and complement data interpretation.
ABSTRACT
Effect of annealing temperature on the structural and optoelectronic properties of pulsed laser
deposited of Cu2ZnSnS4 thin films
1,2
Z. Oulad Elhmaidi , R. Pandiyan1, Z. Sekkat3, M. Abd-lefdil2, and M. A. El Khakani1,*
1
Institut National de la Recherche Scientifique, Centre-Énergie, Matériaux et Télécommunications,
1650 Blvd. Lionel–Boulet, C.P. 1020, Varennes, QC J3X-1S2, Canada
2
Materials Physics Laboratory, Faculty of Sciences, University Mohammed V, Rabat, Morocco
3
Optics & Photonics Center, MASCIR, Rabat, Morocco
*Email : [email protected]
Cu2ZnSnS4 thin films were deposited onto various substrates by using the pulsed KrF-excimer laser
deposition (PLD) technique at room temperature (RT). The PLD-deposited Cu2ZnSnS4 films were postannealed at different temperatures (TA) ranging from 200 to 500°C in Argon atmosphere. The
physical, chemical and optoelectronic properties of the PLD-deposited films were studied as a
function of their TA. The polycrystalline PLD-Cu2ZnSnS4 (CZTS) films were confirmed to crystallize in
the kesterite structure with a strong (112) preferred orientation. Their crystallinity was found to
improve significantly for TA ≥ 400°C. The mean CZTS crystallite size increased from ~ 7 nm (at RT) to 35
nm (for Ta ≥ 400 °C). The SEM analyses revealed that the as-deposited PLD-CZTS films exhibit a
smooth and uniform surface, while the annealed ones (particularly at Ta ≥ 400°C) were found to
consist of densely packed small grains, in agreement with the recrystallization revealed by the XRD
analyses at higher TA. Consistently, the recrystallization of the CZTS films was also found to lead to
increased surface roughness from ~14 nm at RT to 70 nm at TA = 500°C with a value around 40 nm for
TA = 300-400°C. The average composition of the PLD-Cu2ZnSnS4 films, as determined from EDX
analysis, was found to be nearly stoichiometric (Cu/(Zn+Sn) atomic ratio of 1.0-1.2 and a Zn/Sn ratio
of 0.8-0.97) exhibiting Cu-rich and Zn-poor compositions. The analysis of the UV-Vis spectra of the
PLD-Cu2ZnSnS4 films permitted to extract their optical bandgap (Eg), of which optimum value of ~1.58
eV was found for those annealed at TA= 300°C. By combining different characterization techniques
(i.e., UV-Vis, XPS and UPS analysis), we have experimentally determined relevant optoelectronic
parameters (such as the work function, Eg, Valence band maximum, and conduction band minimum)
of the PLD-Cu2ZnSnS4 as function of their TA. This enabled us to reconstruct the energy band structure
of these PLD-CZTS films and examine their band alignment with buffer layer candidates (CdS and ZnS)
for the formation of photovoltaic heterojunctions.
ON-CHIP GENERATION OF FOUR-PHOTON ENTANGLED QUBIT STATES
Christian Reimer1, Michael Kues1,*, Piotr Roztocki1, Benjamin Wetzel1,2, Brent E. Little3, Sai T. Chu4, Tudor Johnston1,
Yaron Bromberg5, Lucia Caspani1,6, David J. Moss7, Roberto Morandotti1,8
1
INRS-EMT, 1650 Boulevard Lionel-Boulet, Varennes, Québec J3X 1S2, Canada; 2Department of Physics and Astronomy, University of
Sussex, Falmer, Brighton BN1 9QH, UK; 3State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision
Mechanics, Chinese Academy of Science, Xi'an, China; 4City University of Hong Kong, Department of Physics and Material Science, Tat
Chee Avenue, Hong Kong, China; 5Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem 91904, Israel; 6School of
Engineering and Physical Sciences, Heriot-Watt University, SUPA, Edinburgh EH14 4AS, UK; 7Center for Micro-Photonics, Swinburne
University of Technology, Hawthorne, Victoria 3122, Australia; 8Institute of Fundamental and Frontier Sciences, University of Electronic
Science and Technology of China, Chengdu 610054, China
Email: [email protected]
Abstract— Multi-photon entangled states are highly desired
for quantum information processing. However, the generation
of multi-partite entangled states is very challenging and usually
requires complex and expensive infrastructure. Here, we
demonstrate that four-photon entangled qubit states can be
generated on a CMOS-compatible chip, opening the door to
compact and scalable implementations. We measure fourphoton quantum interference with a visibility above 89%, and
quantum state tomography reveals a fidelity above 64%.
Keywords—Quantum optics; Integrated
Nonlinear optics, four wave-mixing
optics
devices;
The generation of entangled photon states is required for the
realization of several quantum protocols, which among others can
drastically increase computational speed [1] or enable secure
communication [2]. However, the generation of multi-partite
entangled states [3] is experimentally very challenging and has not
yet been achieved on an integrated platform. A large variety of
different integrated quantum sources has been demonstrated [4],
including the generation of 3-photon correlations (not yet
entangled) [5]. However, until now, no integrated source has
generated more than two entangled photons. Here we report the
first generation of four-photon entangled states on a photonic chip.
For the demonstration of multi-photon entanglement, we use a
CMOS-compatible 4-port integrated micro-ring resonator with a
free spectral range of 200 GHz, and resonances exhibiting Qfactors of 235,000 (820 MHz resonance bandwidth) [6,7]. An
imbalanced phase-stabilized Michelson interferometer was used to
generate the double pulses, required for the time-bin entanglement
scheme, which relies on the coherent superposition of photon pairs
generated in two temporal modes [8]. The double pulses were then
coupled into the ring resonator and photon pairs were generated
through Spontaneous Four Wave-Mixing (SFWM). This quantum
frequency comb emitted entangled photon pairs simultaneously on
all frequency modes, symmetrically with respect to the excitation
frequency [9]. We first confirmed the generation of qubit entangled
𝟏
Bell states 𝚿𝒔𝒊 =
𝐒𝒔 , 𝐒𝒊 + 𝐋𝒔 , 𝐋𝒊 , generated on all
𝟐
frequency mode pairs around the excitation frequency, where the
signal (s) and idler (i) photons are in a quantum superposition of
the short (S) and long (L) time-bin.
In order to combine these multiple individual Bell states to
multi-photon entangled states, the temporal modes of the generated
Bell states need to be indistinguishable, which is achieved in our
configuration through the equal bandwidths of the resonances. We
selected four frequency modes, individually forming two Bell
states, and post-select four-fold photon coincidences. The resulting
entangled state is given by 𝚿𝟒!𝒑𝒉𝒐𝒕𝒐𝒏 = 𝚿𝟏 ⨂ 𝚿𝟐 =
𝟏
𝐒𝒔𝟏 , 𝐒𝒊𝟏 , 𝐒𝒔𝟐 , 𝑺𝒊𝟐 + 𝑺𝒔𝟏 , 𝐒𝒊𝟏 , 𝐋𝒔𝟐 , 𝐋𝒊𝟐 + 𝐋𝒔𝟏 , 𝐋𝒊𝟏 , 𝐒𝒔𝟐 , 𝐒𝒊𝟐 +
𝑳𝒔𝟏 , 𝐋𝒊𝟏 , 𝐋𝒔𝟐 , 𝐋𝒊𝟐 . We confirm the generation of this four-photon
entangled state through four-photon quantum interference with a
measured visibility of 89% without background correction. We
furthermore performed quantum state tomography, which enabled
us to experimentally obtain the density matrix of the generated
quantum state. The calculated fidelity of 64% confirms that the
measured state is close to ideal, where the measured fidelity is
limited by losses and imperfections in the interferometers.
𝟐
Even though the demonstrated multi-photon entangled states
are separable, as they are generated from a product of two-photon
Bell states, it is conceivable that through the use of multiple
excitation fields [10] or controlled phase gates [11], large nonseparable multi-photon entangled states could be constructed. Our
results therefore present a significant step towards enabling optical
quantum information processing on low-cost photonic chips.
I. REFERENCES
[1]
R. Raussendorf et al., “A one-way quantum computer,” Phys. Rev.
Lett. 86, 5188 (2001)
[2]
[3]
H.J. Kimble,“The quantum internet,” Nature 453, 1023 (2008)
H.J. Briegel et al., “Persistent entanglement in arrays of interacting
particles,” Phys. Rev. Lett. 86, 910 (2001)
[4] D. Bonneau et al., “Silicon quantum photonics,” in Silicon Photonics
III, L. Pavesi, D.J. Lockwood, Springer, pp. 41-82.
[5] S. Krapick et al., “On-chip generation of photon-triplet states,” Opt.
Express 24, 2836-2849 (2016)
[6] C. Reimer et al., “Integrated frequency comb source of heralded
single photons,” Opt. Express 22, 6535 (2014)
[7] C. Reimer et al., “Cross-polarized photon-pair generation and bichromatically pumped optical parametric oscillation on a chip,”
Nature Commun. 6, 8236 (2015)
[8] J. Brendel et al., “Pulsed energy-time entangled twin-photon source
for quantum communication,” Phys. Rev. Lett. 82, 2594 (1999)
[9] C. Reimer et al., “Generation of multiphoton entangled quantum
states by means of integrated frequency combs,” Science 351, 11761180 (2015).
[10] M. Chen et al., “Experimental Realization of Multipartite
Entanglement of 60 Modes of a Quantum Optical Frequency Comb,”
Phys. Rev. Lett. 112, 120505 (2014)
[11] G. Vallone et al., “Realization and Characterization of a Two-Photon
Four-Qubit Linear Cluster State,“ Phys. Rev. Lett. 98, 1–4 (2007)
Conical Nanoantenna Arrays for Terahertz Light
A. Rovere*1, A. Toma2, M. Prato2, A. Bertoncini4, A. Cerea2, R. Piccoli1, A. Perucchi3, P.
Di Pietro3 F. De Angelis2, L. Manna2, R. Morandotti1, C. Liberale4, L. Razzari1.
*[email protected]
1
INRS - EMT, 1650 Blvd Lionel Boulet, J3X 1S2 Varennes (Québec), Canada.
Fondazione Istituto Italiano di Tecnologia, via Morego 30, 16163 Genova, Italy.
3
INSTM UdR Trieste-ST, Area Science Park, Basovizza, 34012 Trieste, Italy.
3
KAUST, BESE division, Thuwal 23955-6900, Saudi Arabia.
2
In the last years, plasmonic nanoantennas have been demonstrated to be an
effective solution for localizing free-space light well beyond the diffraction limit, leading to a
local field enhancement that can be exploited, e.g., for enhanced spectroscopy [1]. In this
work, we report a preliminary investigation on the frequency response of 3D gold nanocone
arrays resonating at terahertz (THz) frequencies. First, we numerically investigated them,
to optimize their near- and far-field frequency response. Then, the fabricated sample have
been characterized using broadband synchrotron THz radiation. Experimental results are in
good agreement with simulations and show the potential for nanomaterial spectroscopy.
[1] Toma A. et al., Nano Letters 15, 386–391 (2015).
Integrated Quantum Frequency Comb of Entangled Qubits
Piotr Roztocki,1 Christian Reimer,1 Michael Kues,1,* Benjamin Wetzel,1,2 Fabio Grazioso,1 Yaron Bromberg,3
Brent E. Little,4 Sai T. Chu,5 David J. Moss,6 Lucia Caspani,1,7 and Roberto Morandotti1
INRS-EMT, 1650 Boulevard Lionel-Boulet, Varennes, Québec J3X 1S2, Canada; 2Department of Physics and Astronomy, University of Sussex,
Falmer, Brighton BN1 9RH, United Kingdom; 3Department of Applied Physics, Yale University, New Haven, Connecticut 06520, USA; 4Xi’an
Institute of Optics and Precision Mechanics of CAS, Xi’an, China; 5Department of Physics and Material Science, City University of Hong Kong,
Tat Chee Avenue, Hong Kong, China; 6School of Electrical and Computer Engineering, RMIT University, Melbourne, VIC, 3001 Australia
7
School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, United Kingdom
*[email protected]
1
Entangled photon pair sources form one of the key building blocks for applications in quantum information
processing and computing [1], quantum communication [2], as well as imaging and sensing with resolutions exceeding
the classical limit [3]. To deliver the compactness, scalability and efficiency required by future optical quantum circuit
devices, solutions focusing on an integrated (on-chip) approach have been recently studied and developed, including
integrated quantum circuits, sources and detectors [4]. The use of micro-ring resonators [5,6] with narrow resonances
and high Q-factors are of special interest since, in contrast to waveguides, they offer an enhancement in photon pair
generation efficiency as well as a narrow photon pair bandwidth, rendering them compatible with quantum optical
devices (e.g. high time resolution single photon detectors and quantum memories). More importantly, and in contrast
to non-resonant waveguides, where individual photon pairs featured by one signal/idler frequency pair are typically
produced, resonant nonlinear cavities such as ring resonators offer the possibility of generating correlated photon pairs
on multiple frequency channels [7] due to the periodic and equidistant resonance structure. Here we demonstrate the
first simultaneous generation of multiple entangled photons distributed over a quantum frequency comb [8].
We realized the quantum frequency comb using a 4-port integrated micro-ring resonator with a free spectral range
of 200 GHz, and resonances exhibiting Q-factors of 235,000 (820 MHz resonance bandwidth). The integrated microring resonator was fabricated in a CMOS-compatible high refractive index silica glass [9]. The experimental setup
used a pulsed mode-locked fiber laser (10 MHz repetition rate) to optically pump the resonator. An imbalanced phasestabilized Michelson interferometer was used to generate the double pulses required for the time-bin entanglement
scheme, which relies on the coherent superposition of photon pairs generated in the first or second pulse (i.e. first or
second time-bin) [10]. The double pulses were then coupled into the ring resonator, where their center frequency was
matched with a bandpass filter to a single ring resonance. Due to the high field enhancement and high nonlinearity,
photon pairs were generated through SFWM on several frequency channels (corresponding to the ring resonances)
symmetrically with respect to the pump frequency [7]. We measured the single photon output spectrum, confirming
the ultra broadband nature of the quantum comb, with photon pairs emitted over the full S, C and L telecommunication
band. To verify entanglement through quantum interference, we added interferometers with the path length difference
matched to the first interferometer. Using coincidence detection, this setup allowed to measure both quantum
interference, as well as to perform full quantum state tomography, fully characterizing the entangled photon pairs.
We measured interference patterns for 5 different spectral mode couples symmetric to the pump frequency and
always measured a visibility above 86% (94% background corrected), violating the Clauser-Horne-Shimony-Holt
(Bell-like) inequality (86.9% > 71%≈1/√2) [11], and therefore confirming the observation of time-bin entanglement
from our integrated photon pair source. Performing quantum state tomography [12] revealed that generated entangled
photon pairs form time-bin entangled qubits with a measured fidelity of above 86% and a purity of 99.9%.
In conclusion, we report the first generation of a quantum frequency comb of time-bin entangled photon pairs. The
fully integrated device emits high quality entangled qubits over an extremely broadband quantum comb, covering the
full S, C and L telecommunication band. The comb is particularly appealing for multi-channel quantum
communication, but also for quantum computation, where additional channels increase the information capacity [13].
References
[1] P. Walther et al., “Experimental one-way quantum computing,” Nature 434, 169 (2005).
[2] H. J. Kimble, “The quantum internet,” Nature 453, 1023 (2008).
[3] M. Kolobov, “The spatial behavior of nonclassical light,” Rev. Mod. Phys. 71, 1539 (1999).
[4] D. Bonneau et al., “Silicon quantum photonics,” in Silicon Photonics III, L. Pavesi, D.J. Lockwood, Springer, pp. 41-82.
[5] D. Grassani et al., “Micrometer-scale integrated silicon source of time-energy entangled photons,” Optica 2, 88 (2015).
[6] C. Reimer et al., “Cross-polarized photon-pair generation and bi-chromatically pumped optical parametric oscillation on a chip,” Nature
Commun. 6, 8236 (2015).
[7] C. Reimer et al., “Integrated frequency comb source of heralded single photons,” Opt. Express 22, 1023 (2014).
[8] C. Reimer et al., “Generation of multiphoton entangled quantum states by means of integrated frequency combs,” Science 351(6278), 11761180 (2016).
[9] D. J. Moss et al., “New CMOS-compatible platforms based on silicon nitride and Hydex for nonlinear optics,” Nature Photon. 7, 597 (2013).
[10] J. Brendel et al., “Pulsed energy-time entangled twin-photon source for quantum communication,” Phys. Rev. Lett. 82, 2594 (1999).
[11] J. F. Clauser et al., “Proposed experiment to test local hidden-variable theories,” Phys. Rev. Lett. 23, 880 (1969).
[12] D. F. V. James et al., “Measurement of qubits,” Phys. Rev. A. 64, 052312 (2001).
[13] P. C. Humphreys et al., “Linear optical quantum computing in a single spatial mode,” Phys. Rev. Lett. 111, 150501 (2013).
Coagulation et collage des nanoparticules dans les
plasmas
Benjamin Santos, François Vidal, Claude Boucher
Institut National de la Recherche Scientifique
15 avril 2016
Résumé
Dans le présent travail nous présentons les résultats d’un modèle sectionnel d’aérosol sans dépendence spatiale qui tient en compte les mécanismes de coagulation, collage et nucléation des nanoparticules dans un plasma. Notre modèle est inspiré de la recherche du groupe de S. L. Girshick[1, 2, 3]
qui ont réussi à modéliser la croissance des nanoparticules dans un modèle 1D pour un réacteur de
plasma de silane-argon. L’emploi d’outils numériques s’avère particulièrement pertinent car la mise
en place d’expériences est difficile à réaliser dû à la taille nanométrique des particules. Par exemple,
notre modèle permet de suivre l’évolution des tailles de particules mais aussi des charges.
16
0
14
12
10 8
4
2
10
12
logn̄
8
6
q(1/ e)
6
10
14
20
30
6
40
4
50
20.0
10.0
2
dp(nm)
F IGURE 1 – Logarithme de la densité moyenne dans chaque section.
Références
[1] S. J. Warthesen and S. L. Girshick. Numerical simulation of the spatiotemporal evolution of a
nanoparticle–plasma system. Plasma Chem Plasma Process, 27(3) :292–310, June 2007.
[2] P. Agarwal and S.L. Girshick. Sectional modeling of nanoparticle size and charge distributions
in dusty plasmas. Plasma Sources Sci. Technol., 21(5) :055023, October 2012.
[3] L. Ravi and S. L. Girshick. Coagulation of nanoparticles in a plasma. Phys. Rev. E, 79(2) :026408,
February 2009.
Chondroitin sulfate-oriented epidermal growth factor (EGF) coating for
random and aligned electrospun vascular grafts
Houman Savoji1,2,5, Marion Maire2, Pauline Lequoy2,4, Benoît Liberelle3,
Gregory De Crescenzo1,3, Michael R. Wertheimer1,5, Abdellah Ajji1,3, Sophie Lerouge2,4
École Polytechnique de Montréal, Montreal, QC, Canada (1Institute of Biomedical Engineering,
3
2
Department of Chemical Engineering, 5Department of Engineering Physics)
Laboratory of Endovascular Biomaterials (LBeV), Research Centre, Centre Hospitalier de
l’Université de Montreal (CRCHUM), Montreal, QC, Canada
4
Department of Mechanical Engineering, École de technologie supérieure, Montreal, QC,
Canada
Introduction: The patency of synthetic small-diameter vascular grafts (SDVG) is limited by the
absence of formation of a stable monolayer of endothelial cells (HUVEC) on the lumen, resisting
to physiological shear. Electrospinning is an interesting fabrication process which enables to
create new SDVG with enhanced compliance and to mimic the morphology of tissues. However
cell adhesion and growth remains a problem. The objective here has been to investigate random
(R) and aligned (A) electrospun PET (ePET) mats as scaffolds for luminal and media layers with
bioactive coatings that improve cell behavior.
Methods: (R) and (A) mats were prepared by electrospinning. The mats were then coated with
amine-rich plasma coating (LP). Chondroitin sulfate (CS) was covalently grafted, following
which epidermal growth factor (EGF) was oriented tethered. The physicochemical properties of
the mats were then characterized. The metabolic activity, morphology and infiltration of HUVEC
and VSMC were assayed. EC resistance to shear was also studied.
Results and Discussion: Significant increase of HUVEC metabolic activity was observed on
bioactive coatings (LP+CS) compared with bare mat. These cells formed a confluent monolayer,
and their retention was greatly improved on both LP- and LP+CS-coated mats, both (R) and (A),
results being better for (A). For the media layer, CS+EGF coatings led to dramatically increased
VSMC -growth, -infiltration and -survival in serum-free medium.
Conclusion: Combinations of bioactive coatings with ePET mats can provide promising
scaffolds for luminal and media layers of SDVGs, ones that greatly improve cell growth, VSMCinfiltration, and HUVEC-resistance to shear.
This project was supported by the CIHR and NSERC. HS gratefully acknowledges the award of
FRQNT and SVC Foundation scholarships.
Broadband detection of THz pulses via silica based solid-state device
A. Tomasino1,5, A. Mazhorova1, M. Clerici2, M. Peccianti3, S. P. Ho1,4, L. Razzari1, Y. Jestin1, A. Pasquazi3,
A. Markov1, A. Busacca5, J. Ali4, R. Morandotti1
1
INRS-EMT, 1650 Boulevard Lionel-Boulet, Varennes, Québec J3X 1S2, Canada
School of Engineering, University of Glasgow, Glasgow, G12 8LT, United Kingdom
3
Department of Physics and Astronomy, University of Sussex, Falmer, Brighton BN1 9RH, United Kingdom
4
Nanophotonics Research Alliance, Universiti Teknologi Malaysia Skudai, Johor, Malaysia
5
DEIM, University of Palermo, Viale delle Science, Palermo, 90128, Italy
2
Terahertz (THz) technology gained significant interest over the last years, mainly due to its unique properties,
enabling the development of several applications in biosensing, security, and defense fields. Although highquality and reliable THz sources are available on the market, still there are mainly two techniques suitable for
the coherent detection of THz pulses, i.e., Electro-Optic Sampling and Photoconductive Antennas. However,
these techniques allow relatively narrowband THz detection, usually below 4 THz, due to absorption and
dispersion inside the nonlinear crystals. In order to overcome such a limitation, some broadband coherent
detection schemes have been proposed and, among others, the Air Based Coherent Detection (ABCD) technique
(0.1 - 20 THz) is still the most employed [1]. It relies on the Terahertz Field Induced Second Harmonic (TFISH)
generation process in centrosymmetric media (for example, air). Since THz radiation can be regarded as a static
electric field compared to a fast oscillating optical beam, it can break the symmetry of a Kerr medium, thus
leading the material to show a quadratic behavior. By applying an external oscillating bias, it is possible to
recover the THz waveform. However, the ABCD technique requires bulky optical components and both a high
probe power and a high bias voltage (~5 kV) in order to achieve suitable signal-to-noise (SNR) ratios. The
proposed device relies on the TFISH effect (similar to the ABCD protocol), exploiting the advantages of the
large breakdown voltage and the high nonlinearity of Silica (SiO2). The sample has been fabricated via standard
UV lithography, depositing 100-nm thick gold electrodes on a 1-mm thick fused silica substrate (Fig. 1(a)). The
gap between the electrodes was filled with a 2 μm-thick layer of SiO2 on the top in order to avoid breakdown in
air. Thanks to the micron-size gap, very strong electric fields can be achieved up by applying a bias voltage of
few hundreds volts. Different combinations of gold fingers (10, 30, 100 µm) and silica gap sizes (3, 4, 5 µm)
were tested. Asymmetric periodic structure has been chosen in order to avoid any destructive interference during
detection. The THz waveforms recovered by employing the 3 µm gap, 10 µm finger sample are shown in Fig.
1(b) as a function of the applied voltage biases. The THz signal linearly scales with the applied bias, however a
degradation is observed over 500 V. On the other hand, SNR measurements indicated that the optimal operating
condition is achieved for a bias voltage equal to 200 V, which is one order of magnitude lower than the value
needed for the ABCD case in order to obtain comparable performance, as shown in Fig. 1(c). Our results pave
the way to a novel approach towards compact, integrated broadband coherent detectors for THz pulses.
Figure 1. (a) Sketch of the micro-slit asymmetric array solid-state THz detector. (b) THz waveforms recovered with the 3
µm gap, 10 µm finger device, in the range 50-600 V applied bias. (c) Comparison between the spectra achieved in the case
of the standard ABCD (blue) and proposed solid-state THz detector (red, SS-BCD) technique.
References
[1] X. Lu and X. C. Zhang, “Balanced terahertz wave air-biased-coherent-detection,” Appl. Phys. Lett. 98, 151111 (2011).
Structure et propriétés électriques de couches minces Sm0.6Ndo.4NiO3 épitaxiées
Badr Torriss et Mohamed Chaker
Depuis quelques années les isolants de Mott ont suscité une attention particulière de la
part de la communauté scientifique, en raison de leurs propriétés physiques exceptionnelles.
Parmi ses isolants, les nickelâtes de terres rares dont la formule générale est RNiO3 (R : Cation
terre-rare). Ces composés présentent en fonction de la température, un comportement métallique
paramagnétique, isolant paramagnétique ou isolant antiferromagnétique [1].
En contrôlant la composition chimique des solutions solides de différents nickelâtes de
terres rares, la température de transition métal-isolant TMI peut-être rapprochée de la température
ambiante [2], ce qui ouvre la voie à de multiples applications dans le domaine de
l’optoélectronique à savoir, les transistors à effet de champs [3], les modulateurs optiques [4] et
les fenêtres éco-énergétiques [5].
L’objectif de ce travail est d’étudier l’influence des contraintes d’épitaxie (compressive et
tensile) sur les propriétés structurales, morphologiques et électriques des couches minces de la
solution solide Sm0.6Nd0.4NiO3 (SNNO) pour lesquelles la température de transition MI est de
l’ordre de 313 K. Nous nous sommes concentrés dans un premier temps à établir un lien entre la
déformation structurale de la maille et la température de transition MI. Par la suite, les différents
mécanismes de conduction par saut dans les couches minces de SNNO élaborées sur différents
substrats comme SrLaAlO4, LaAlO3 et SrTiO3 ont été étudiés. Les résultats expérimentaux de
variation de la résistivité en fonction de la température de différents films de SNNO révèlent la
possibilité de coexistence de plusieurs modes de conduction par saut entre les états localisés à très
basse température.
[1]
[2]
[3]
[4]
[5]
M. Medarde, J. Phys.: Condens. Matter 9 1680 (1997).
R. D. Sánchez, M. T. Causa, A. Seoane, J. Rivas, F. Rivadulla, M. A.López-Quintela, J. J.
Pérez Cacho, J. Blasco, and J. García, J. Solid State Chem. 151, 1 (2000).
C. H. Ahn, J.-M. Triscone and J. Mannhart, nature 424, 1015 (2003).
Luke A. Sweatlock and Kenneth Diest, Optics Express Vol. 20, Issue 8, 8700-8709
(2012).
J. R. Skuza, D. W. Scott, R. M. Mundle, and A. K. Pradhan, Scientific Reports 6, 21040
(2016).
Développement de procédés plasmas pour la microélectronique :
PECVD double fréquence à injection liquide pulsée et Plasma ALD
C. Vallée1, R. Gassilloud2, R. Vallat1,2, F. Piallat3, A. Aoukar1, P. Kowalczyk1,2,
P.D. Szkutnik1, P. Noé2, T. Wakrim1, and P. Gonon1
1
Univ. Grenoble Alpes, LTM, CEA-LETI-Minatec, F-38000 Grenoble, France
2
CEA, LETI, Minatec Campus, F-38054 Grenoble, France
3
Altatech Semiconductor, 611 rue Aristide Bergès,38330 Montbonnot-Saint-Martin, France
Avec cette présentation nous allons d’abord discuter des évolutions des procédés plasmas
et des matériaux élaborés par PECVD et PEALD pour la microélectronique. En effet si
pendant de nombreuses années l’amélioration des dispositifs en microélectronique s’est
faite via une simple réduction d’échelle des dimensions, depuis le début des années 2000,
c’est l’intégration de nouveaux matériaux (tel que HfO 2) et de nouveaux procédés
(ALD/PEALD) qui a permis de poursuivre cette amélioration. Les limites technologiques
actuelles en terme de dimension imposent aussi de réfléchir à des nouveaux matériaux et
procédés permettant de créer des nouveaux dispositifs ou nouvelles architectures
(transistor ou mémoire flash 3D, mémoires non-volatiles résistives RRAM ou à changement
de phase PCM…).Pour chacun de ces dispositifs un procédé plasma spécifique doit être
développé.
Suite à cette « introduction » nous présenterons quelques exemples de procédés plasmas
développés ces dernières années :
-
Procédés PECVD avec plasma double fréquence (400 KHz et 13.56 MHz) et injection
liquide de précurseurs pour le dépôt du métal TiCN dans un empilement high K/grille
métal de transistor CMOS et pour le dépôt confiné de matériaux à changement de
phase GeTe ou GeSbTe. Avec ces exemples nous montrerons que l’ajout d’une
puissance basse fréquence impacte fortement la densité du plasma et la dissociation
des précurseurs. Ceci modifie alors les propriétés du dépôt : vitesse, qualité des
couches, capacité à remplir des trous pour un dépôt dans des structures confinées.
-
Procédé PEALD et PVD pour des mémoires résistives non volatiles RRAM (Memristor)
et des dispositifs à variation de capacité (MEMCapacitor ou MemImpedance). Le but
ici est d’utiliser les procédés de dépôt plasma pour fabriquer des couches
nanométriques d’isolants dont le claquage peut être contrôlé de manière réversible.
-
Développement d’un procédé PEALD pour le dépôt sélectif d’oxydes. La complexité
de la lithographie pour des dimensions nanométriques tend à modifier l’approche
Top Down classique du dépôt de matériaux (on dépose dans un trou via un masque ou
pleine plaque puis on grave). Le challenge désormais est d’être capable d’avoir une
croissance sélective vis-à-vis d’une surface et ainsi un dépôt plasma suivant une
approche bottom up.
Pour la plupart de ces applications nous montrerons que l’utilisation de la spectroscopie
d’émission optique (OES) permet d’optimiser et de comprendre le procédé.
Silver Tip Manufacturing for Tip-Enhanced Raman Spectroscopy via
Electrochemical Etching
Jiawei Zhang1, Gitanjali Kolhatkar1, Julien Plathier1, Andreas Ruediger 1
1
Nanoelectronics-Nanophotonics, INRS-Énergie Matériaux et Télécommunications,
1650 Lionel-Boulet, Varennes, Québec, J3X1S2, Canada
Conventional scanning probe microscopy (SPM) offers topography images with a
resolution down to nanometer scale, but is limited by its inability to provide chemical and
structural information regarding the sample under study. On the other hand, optical spectroscopy
methods such as Raman spectroscopy can provide us with abundant chemical and structural
information. However, due to its diffraction limit, the sensitivity of Raman spectroscopy is
limited to several hundred nanometers. Tip-Enhanced Raman Spectroscopy (TERS), a newly
developed characterization technique, combines the virtues of SPM techniques and optical
spectroscopy. By utilizing a localized surface plasmon at the apex of a metallic tip, or
nanoantenna, the topography can be recorded simultaneously with the Raman spectrum with a
spatial resolution down to ~1 nm.1 The core element in TERS is the tip, since it is the source of
the enhancement while determining the maximum resolution that can be obtained. However, the
utilization of TERS is currently limited by the availability of suitable tips with high enhancement,
good stability as well as high reproducibility.2
Silver, with its intrinsic low electric damping, high free electron density, strong localized
surface plasmon resonance (LSPR) effect in the visible region, is a promising material for the
nanoantenna. However, it is prone to contamination, which limits its usage in TERS. In this work,
we propose a new etching recipe, namely a mixture of hydrophosphoric acid (H3PO4) and
acetonitrile (C2H3N) to overcome this limitation. The influence of the etching medium
concentration on the properties of tips is studied. Besides, with an updated version of a cutoff
circuit, we successfully avoid over-etching, a most commonly confronted challenge in tip
manufacturing process. We have determined the threshold of cutoff voltage for tips with
promising properties by a series of experiments. Up to now, the silver tips made from our recipe
show very little or no contamination according to Raman studies, and also give satisfying
topography with radii of 100 nm or less. Our work will lead to the development of high quality
silver tips for TERS, enabling the chemical and morphological study of a wide variety of
materials at the nanoscale.
[1] Achim Hartschuh, Angew. Chem. Int. Ed. (2008), 47, 8178 – 8191
[2] Teng-Xiang Huang et al, Anal Bioanal Chem. (2015) 407, 8177–8195
Synthesis of Au and Pt-Au Alloy Nanoparticles
Qingzhe Zhang, Zhenhe Xu, Yanlong Liu, Mohamed Chaker*, Dongling Ma*
Institut National de la Recherche Scientifique, INRS-Énergie, Matériaux et Télécommunications, 1650 Boulevard
Lionel-Boulet, Varennes, Québec J3X 1S2, Canada
Au nanoparticles (AuNPs) have attracted increasing attention because of their unique catalytic properties.
Their synthesis with the conventional wet-chemistry method will leave some organic ligands on the
surface, which can act as barriers between reactants and surface active sites, decreasing their catalytic
activities. We report an approach to fabricate “bare and clean” Au NPs by means of pulsed laser ablation
in liquid. Furthermore, we extend this method to synthesize Pt-Au alloy NPs. For this purpose, we are
now optimizing the laser-target conditions, such as laser fluence as the liquid environment (pH value), to
synthesize high surface quality Pt-Au alloy NPs that could be applied for visible-light photodegradation
and water-splitting.
Key words: Au nanoparticles; Pt-Au alloy nanoparticles; pulsed laser ablation; photodegradation; watersplitting
Presenting author’s email: [email protected]

Abstracts - Plasma Québec

Transcription

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