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

P Si (W/cm 2 )
x = 0/Si
Bruggemann
Si excess (at.%)
vol. fraction
from refractive
index
(agglomerated)
1.62 1.33 15.28
1.77 1.2 18.89
2.07 1.08 23.08
2.22 1.04 24.34
2.37 1.04 24.34
2.66 1.029 24.9
2.96 0.943 28.18
Table 3.6: Si excess estimation (agglomerated Si) from Bruggemann method.
tel-00916300, version 1 - 10 Dec 2013
It can be seen that the Si excess values are high as estimated from Bruggeman
method, than the other two methods. Besides, it can be seen that there is minimal
variation in Si excess for cases of intermediate values of P Si : 2.07 to 2.66 W/cm 2 .
3.4.2 Eect of annealing
From the above investigations, it is clear that SRSO grown by method 3 incorporates
the highest Si excess compared to the other two methods. The eect of annealing
on the material properties has to be analyzed before nalizing the method 3 SRSO
for multilayers. A high Si excess may result in formation of big Si-np leading to
loss of the desired quantum connement eects whereas a low Si excess would mean
lower absorption coecient which is not suitable for the objective of this work.
Therefore SRSO sample with intermediate parameters of r H = 26% and P Si = 2.22
W/cm 2 were chosen in order to balance between deposition rate and Si excess. T d
= 500°C was chosen since it was demonstrated in this work that this temperature
favours Si excess, and also forms some Si-np in the as-grown state as reported in
[Hijazi 09a]. The SRSO sample with these optimized parameters are analyzed for
structural and optical properties with regard to annealing. This sample will be
referred as SRSO-P15 in the forthcoming discussions. The thickness and refractive
index at 1.95 eV of this sample as estimated from ellipsometry are 565 nm and 2.02
respectively. According to RBS results 2 , this sample is SiO x=0.72 with 37 at.% Si
excess. Five pieces of this sample were annealed at 1000°C during 1 minute, and at
700°C, 900°C, 1000°C and 1100°C during 1 hour in N 2 atmosphere. Unless stated
otherwise, all the studies in this section are carried out on SRSO-P15.
2 RBS analyses were made by J. Perriére at UNIV PARIS 06, INSP NANOSCIENCE PARIS,
CNRS, UMR 7588, F-75015, Paris, France.
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