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

the host SiO 2 matrix leading to an increase in n 1.95eV . This method is thus advantageous
than method 1 since by controlling the ratio of power densities between Si
and SiO 2 it is possible to incorporate higher Si excess at a higher r d .
3.3.2 Fourier transorm infrared spectroscopy
Figures 3.8a and 3.8b show the FTIR spectroscopy of the co-sputtered SRSO samples
recorded in Brewster and normal incidences respectively. In all the spectra the TO 3
peak position is normalized to unity for comparison.
tel-00916300, version 1 - 10 Dec 2013
(a) Brewster incidence.
(b) Normal incidence.
Figure 3.8: FTIR spectra of co-sputtered SRSO in (a) Brewster incidence and (b) normal
incidence. The straight line in the normal incidence spectra helps to witness the shift of
v T O3 and the arrows indicate the 1107 cm −1 peak.
With an increase in P Si , the LO 3 peak position shifts from 1220 cm −1 to 1187
cm −1 , in addition to a progressive decrease of its intensity. The TO 3 peak position
also shifts towards lower wavenumbers as can be seen from the normal incidence
spectra. The FTIR spectra with increasing P Si show the same behaviour as those
shown when r H was increased. Hence the same explanations as detailed in section
3.2.2 are valid. The only dierence in these spectra as compared to method 1, is
the absence of the Si-H peak between 870-890 cm −1 indicating these samples were
fabricated under a pure Ar plasma. The increased Si incorporation as denoted by
the high refractive index with increasing P Si can also be seen from the FTIR spectra.
71