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

4.2 N 2 -Reactive sputtering of Si cathode
The SiN x layers were grown by sputtering Si cathode in a nitrogen rich plasma. The
RF power density applied on the Si cathode (P Si ) and the time of deposition were
xed at 4.44 W/cm 2 and 3600s respectively. The reactive gas rate r N was varied
between 5.1%-16% in order to change the composition of the material (as indicated
by the refractive indices) between stochiometric and Si-rich SiN x layers. Table 4.1
details the conditions used in this thesis, for obtaining N 2 -rich plasma.
tel-00916300, version 1 - 10 Dec 2013
P Ar (mTorr) P N2 (mTorr) r N (%)
14.8 0.8 5.1
14.1 1.1 7.1
14 1.5 9.6
13.6 1.9 12
12.8 2.5 16
Table 4.1: Conditions used to obtain N 2 − rich plasma.
4.2.1 Refractive index (n 1.95eV ) and Deposition rates (r d )
Figure 4.1 shows n 1.95eV and r d of the samples with regard to r N .
Figure 4.1: Eect of r N on refractive index (left axis)
and deposition rate (right axis).
The refractive indices increase
with decreasing r N , thereby
making the material Si-rich. It
can be seen that by varying r N ,
n 1.95eV changes between 2.01 to
3.3 which indicates that the
composition can be tuned between
Si 3 N 4 and Si. The deposition
rate can be seen to decrease
with increasing r N . This
is attributed to the diculty in
sputtering the target when r N is
high, as observed in other sputtering
set-ups in our team as
well. The value, n 1.95eV ∼ 2.4 was chosen for most of the MLs to obtain a SRSN
sublayer.
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