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

(a) Normal Incidence.
(b) Oblique (Brewster) Incidence.
tel-00916300, version 1 - 10 Dec 2013
Figure 2.5: Typical FTIR spectra of SiO 2 which is decomposed into three and ve
gaussians in the normal incidence and Brewster incidence spectra respectively.
LO 4 -TO 4 , which is assigned to disorder-induced mode in the SiO 2 matrix [Kirk 88].
The presence of these vibrational modes are sometimes overlapping and hence a
curve tting within the range of interest was perfomed using gaussian functions to
resolve the peaks and estimate their positions.
Table 2.1 summarizes the characteristic vibrational frequencies of SiO 2 as compiled
from [Lehmann 83, Pai 86, Innocenzi 03].
Peak position (cm −1 ) Vibrational Modes
460 TO 1 Si-O rocking
507 LO 1 Si-O rocking
810 TO 2 Si-O symmetric stretch
820 LO 2 Si-O symmetric stretch
1080 TO 3 Si-O antisymmetric stretch
(adjacent O atoms in phase)
1256 LO 3 Si-O antisymmetric stretch
1150-1200 LO 4 -TO 4 Si-O antisymmetric
stretch (adjacent O atoms out of
phase - disorder induced mode).
Table 2.1: Characteristic FTIR vibrational frequencies of SiO 2 .
Informations extracted in this thesis
ˆ The dierent types of bonds such as Si-O, Si-H, Si-N, Si-ON, N-H etc., are
detected from the position of the longitudinal and transverse optic modes.
37