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

(d) Photoluminescence
Figure 3.14a shows the PL spectra of SRSO-P15 at various annealing treatments.It
can be seen that there is no emission whatever be the annealing conditions. The
absence of PL may be attributed to high Si excess due to any/all of the following
processes:
(i) an increase in the non-radiative paths in the matrix.
(ii) a higher disorder in the matrix as observed by FTIR investigations.
(iii) possible formation of oversized Si-np upon annealing, leading to the loss of
quantum connement eect.
tel-00916300, version 1 - 10 Dec 2013
(a) PL spectra vs. annealing of SRSO-P15.(b) PL intensity vs. n 1.95eV
of Method 3 SRSO.
Figure 3.14: PL spectra of (a) SRSO-P15 sample at various annealing and (b) Other
SRSO samples grown by method 3 but with lower refractive index.(*) indicates second
order laser emission.
This is conrmed by the presence of luminescence witnessed in other samples
grown using method 3, that have lower refractive index and therefore lower Si excess
in the matrix (Fig. 3.14b).
(e) Absorption coecient
The values of absorption coecients (α) between 1.5-4.5 eV were extracted from k
values obtained by ellipsometry measurements as detailed in section 2.2.6 of chapter
2. Figure 3.15 represents the absorption coecient curves of SRSO-P15 before and
after dierent annealing treatments.
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