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

2. Possible formation of Si-O-N bonds at the interface of SRSO and SRSN
sublayers.
3. It has been reported in SiN x monolayers that the presence of nitrogen atoms
as the next nearest neighbours would induce a shift of the TO mode towards higher
wavenumbers [Molinari 03]. The same proposition can be assumed in the case of
SRSO/SRSN MLs.
tel-00916300, version 1 - 10 Dec 2013
In addition to these peaks, it also has to be remembered that the (LO 4 -TO 4 ) Si−O
modes may also contribute to the shape and peak positions of the FTIR spectra.
Similarly the normal incidence spectrum also shows the contribution of Si-O from
SRSO and Si-N from SRSN layers (Fig. 4.19b) and is tted with four peaks. The
two major peaks centered around 1058 cm −1 and 887 cm −1 can be unambiguously
attributed to the (TO 3 ) Si−O and TO Si−N modes respectively.
Figure 4.20: FTIR spectra of as-grown and CA
100(3.5/5) ML.
The presence of Si excess
in SRSO sublayer is attested
by the shift of the (TO 3 ) Si−O
peak position towards lower
wavenumbers as compared to
that in SiO 2 (∼1080 cm −1 ).
The less intense peaks around
1186 cm −1 and 806 cm −1 can be
attributed to the TO 4 and TO 2
modes of Si-O respectively.
Figure 4.20 shows the the
FTIR spectra of as-grown and
CA 100(3.5/5) ML recorded
in Brewster and normal incidences.
The position and intensity
of the FTIR bands is a result
of an overlapping contribution from Si-O and Si-N modes thereby making the
analysis complicated. Hence the identication of the peaks are very dicult after
annealing and the tting of peaks are therefore not appropriate. The approximate
peak positions of the dierent vibration modes are indicated on the top part of the
gure. From a comparison of the overall shape of the spectra obtained from the
as-grown and CA samples, it can be seen that the Brewtser incidence spectra show
a blueshift (towards higher wavenumber) of the peak maximas.
The blueshift of the Si-O modes with annealing is indicative of the formation
of Si-np in SRSO sublayer. This is conrmed by the increase of (LO 3 ) Si−O mode
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