Films minces à base de Si nanostructuré pour des cellules ...

Inelastic (Raman and Brillouin) scattering. A part of the photons is re-radiated
at the incident energy and this is known as Rayleigh scattering. Few photons are
scattered due to interaction with optical and acoustical phonons in the material
and are termed as Raman and Brillouin scattering respectively. The energy shift of
the Raman scattered light towards high (Anti-stokes) and low (Stokes) frequencies
yield information on the vibrational modes in the measured sample. Figure 2.11
illustrates the Raman shift of the scattered light.
tel-00916300, version 1 - 10 Dec 2013
Figure 2.11: Illustration of scattering of light and Raman shift.
Experimental set-up and working
A Raman system typically consists of four major components:
ˆ Excitation source (Laser),
ˆ Sample illumination system and light collection optics,
ˆ Wavelength selector (Filter or Spectrophotometer),
ˆ Detector (Photodiode array, CCD or PMT).
The schematic diagram of a Raman spectrometer is as shown in gure 2.12.
The sample under investigation is illuminated with a laser beam. The scattered
light is collected with a lens and is sent through a notch lter which removes the
scattered light that is of the frequency of the laser beam. Only the light that has an
energy shift (Raman shifted light) passes through the lter. The movable grating
disperses the light and the dierent wavelengths are collected by a charged couple
device (CCD) camera. Raman spectrometer from Jobin Yvon equipped with Ar
44