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

Figure 4.45: Surface microstructure of 50(3.5/5) ML after N 2 , FG and N 2 +FG annealing
as observed by optical microscope.
tel-00916300, version 1 - 10 Dec 2013
whatever the annealing time or the number of patterns (not shown here). Thus, we
can say that the surface microstructural changes after annealing does not inuence
the emission intensity, and may only reect the exodiusion paths for gases.
To conclude on our analysis in this section on the possible origin of emission, we
may attribute the peak between 1.50-1.7 eV (peak 2) to Si-np in SRSO sublayers and
1.8-1.95 eV (peak 3) to SRSN sublayer contribution due to some defects. However
at this stage it is dicult to understand the type of defects in SRSN sublayers. The
origin of the low energy peak still remains unclear. The possibility of interference
eect or the presence of another kind of emission centers leading to this emission
will be analyzed in chapter 5 by theoretical modeling and simulations.
4.11 Summary on SRSO/SRSN MLs
A detailed analysis on the structural and optical properties of SRSO/SRSN MLs was
made. It was shown that the structures of the MLs obtained with SRSN grown by
reactive sputtering approach and co-sputtering approach are the same, and exhibit
similar trend in emission properties.
Ellipsometry : Results from ellipsometry simulation give the refractive indices
and total thickness of the ML within 5% error and indicates the appearance of voids
on the ML surface after annealing. An increase in refractive index accompanied by
a decrease of the thickness on annealing suggests the densication process.
XRR and TEM: The XRR spectra shows the presence of repetitive patterns
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