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

P Ar (mTorr) P H2 (mTorr) r H (%)
14.4 0.7 4.6%
10.5 1.4 11.7%
8.1 2.9 26%
4 5.3 57%
Table 3.3: Conditions used to obtain hydrogen-rich plasma.
3.2.2 Eect of hydrogen gas rate (r H )
tel-00916300, version 1 - 10 Dec 2013
Four layers of SRSO with varying r H were grown at T d = 500°C. Table 3.3 shows the
values of partial pressures of Ar and H 2 and the corresponding r H .
Since the hydrogen in the plasma leads to two competing phenomena as described
above, it becomes important to see how the hydrogen rate in the plasma inuences
the compositional and structural properties of SRSO layers.
(a) Deposition rate (r d ) and Refractive Index (n 1.95eV )
The evolution of r d and n 1.95eV with respect to r H introduced into the plasma are
shown in gure 3.5. It can be seen that there is a steady decrease in r d with increase
in r H from 4.6% to 57%. On the contrary, n 1.95eV value increases with increasing
r H .
Figure 3.5: Eect of r H % on the deposition rate (r d ) nm/s (left axis)and refractive index,
n 1.95eV (right axis).
When hydrogen is introduced in the plasma,
ˆ the Si-Si bonds are broken leading to the removal of Si atoms from the surface
[Tsai 89, Drévillion 93, Akasaka 95]. This selective etching leads to a decrease
in r d on increasing r H from 4.6%-57%.
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