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

Figure 4.9: Eect of P Si on refractive indices and deposition rates of co-sputtered SiN x
materials. (r N =5.1% and 7.1% were used for Si 3 N 4 and NRSN layers respectively).
tel-00916300, version 1 - 10 Dec 2013
4.3.2 Structural analysis
(a) Fourier transform infrared spectroscopy
Figure 4.10a shows a typical FTIR spectra of NRSN, Si 3 N 4 and SRSN samples
obtained from layers with n 1.95eV = 1.9, 2.01 and 2.32 respectively. Similar to the
samples obtained by the rst deposition approach, these samples also possess only
the Si-N bonds and hence the discussions in section 4.2.2 are valid here. The contribution
from Si substrate is witnessed by a peak around 1107 cm −1 in the normal
incidence, whereas in the Brewter incidence it is overlapped by the LO Si−N mode.
The LO Si−N and TO Si−N modes shift towards higher wavenumbers with increasing
Si incorporation as indicated in the table of gure 4.10a. The evolution of FTIR
spectra obtained from SRSN samples with varying refractive indices is shown in gure
4.10b. The decreasing LO Si−N /TO Si−N ratio with refractive index (increasing
Si excess) can be well noticed. The trends observed in these samples are exactly
similar to those observed in reactively sputtered SiN x samples (ref. Fig. 4.3).
The eect of annealing on the structure of as-grown and annealed (STA, 1h-
900°C and CA) Si 3 N 4 (Fig. 4.11a) as well as Si-rich SiN x sample (Fig. 4.11b) were
investigated.
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