Directional surface enhanced Raman scattering on gold nano

ABSTRACTS
_______________________
ICES
2015
T.Th4
Directional surface enhanced Raman scattering on gold nano-gratings
Raymond Gillibert1,2, Mitradeep Sarkar3 Jean-François Bryche3,4, Ryohei Yasukuni1, Julien Moreau3, Mondher Besbes3, Grégory Barbillon4, Bernard Bartenlian4,
Michael Canva3, 5 and Marc Lamy de la Chapelle1
1
Université Paris 13, Sorbonne Paris Cité, Laboratoire CSPBAT, CNRS UMR 7244, Bobigny, France
2
HORIBA Jobin Yvon S.A.S. Villeneuve d'Ascq, 231 rue de Lille 59650 Lille, France
3
Institut d'Optique Graduate School, Laboratoire Charles Fabry CNRS UMR 8501, Palaiseau, France
4
Université Paris-Sud, Institut d'Électronique Fondamentale CNRS UMR 8622, Orsay, France
5
Université de Sherbrooke, Laboratoire Nanotechnologies Nanosystèmes, LN2, UMI CNRS 3463,
3IT. Qc Canada.
Raymond Gillibert: [email protected]
Directional extinction spectrum and SERS intensity were investigated for 1D and 2D gold
nanostructure arrays deposited on flat gold layer (fig. 1b): three different nanolines gratings with different periods (300, 400 and 500 nm), deposited on a 30 nm gold film and two arrays of nanodisks
with diameter of 220 nm and with a period of 400 nm (one on gold layer and the other directly on
glass substrate). The angle of incident light was varied by tilting the substrates (fig. 1a). Extinction
spectrum of both arrays showed other intense resonance bands apart from the localized surface plasmon band of the nanostructures. These bands are red-shifted with increasing incident angle and systematic extinction analysis of different grating periods revealed that the observed bands are due to an
excitation of propagating surface plasmon on flat gold surface, which fulfills Bragg condition of the
arrays (Bragg mode). Directional SERS measurements were performed at three different wavelengths
(633, 660 and 785 nm). They demonstrated the SERS intensity increased up to an order of magnitude,
when Bragg mode Plasmon is excited (fig. 1c) whereas there is no visible angular dependence of the
SERS intensity without the gold film (black scatter). Moreover the SERS signal, for all incident angles, is much higher with a gold film under the nanostructures, indicating that Bragg mode causes a
significant enhancement of SERS intensity. Hybridized numerical calculations of Finite Element
Method and Fourier Modal Method also justified the presence of Bragg mode Plasmon and illustrated
that the enhanced electric field is particularly localized around the nanostructures regardless of their
size.
Bragg
Mode
Fig. 1. (a) Scheme of the setup used for extinction and SERS measurements. (b) SEM image of nanodisks array of diameter 220 nm and
period 400 nm. The scale bar is 500 nm long. (c) Experimental SERS intensity as a function of tilt angle for nanodisks arrays on glass substrate (black scatter) and on gold film (red scatter). The excitation wavelength is 660 nm and the grating’s period is 400 nm.