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

The LO 3 and TO 3 peaks approach each other, resulting in the increasing intensity
of LO 4 -TO 4 doublet. This is an indication that the increasing Si excess induces
disorder in the deposited layer. Since the peak around 1107 cm −1 appears from
P Si = 2.07 W/cm 2 onwards and increases gradually with increasing power applied
on Si cathode, we can conrm that this peak is associated with Si excess. This peak
thus can be attributed to be a combined contribution of increasing disorder in the
matrix and agglomeration of Si with interstitial oxygen.
(c) Si excess estimation
tel-00916300, version 1 - 10 Dec 2013
P Si (W/cm 2 ) ν T O3 x = 0/Si
from
FTIR
Si excess
(at.%) from
FTIR
(unbonded
Si)
x = 0/Si
from ellipsometry
Si excess
(at.%)
from
ellipsometry
(agglomerated
Si)
1.62 1046 1.62 7.25 1.75 5.4
1.77 1045 1.61 7.47 1.68 6.7
2.07 1042 1.57 8.2 1.64 7.6
2.22 1042 1.57 8.2 1.57 9.2
2.37 1041 1.56 8.45 1.57 9.2
2.66 1040 1.55 8.8 1.50 10.8
2.96 1039 1.54 8.96 1.43 12.57
Table 3.5: Si excess estimation by FTIR and refractive index (Bruggeman method)
analysis with varying P Si .
The Si excess estimated from FTIR (unbonded Si) within an uncertainity of
±0.2% and ellipsometry (Bruggeman method-agglomerated Si) analysis within an
uncertainity of ±3% are given in table 3.5. Comparing with the results of previous
deposition approach (ref. Tab. 3.2), it can be noticed that the increase of P Si leads
to an increase in Si excess estimated from both FTIR and ellipsometry methods.
This can be attributed to the increasing RF power density applied on the Si target
that favours the incorporation of isolated Si (i.e. unbounded Si) as well as the
formation of Si-np (i.e. agglomerated Si).
3.4 Reactive Co-sputtering- Method 3
In order to take advantage of the above described two methods, in favouring the
incorporation of Si excess within the SiO 2 matrix, reactive co-sputtering method is
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