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

Aim of the study
To see the inuence of
hydrogen plasma
Deposition / placing
in hydrogen- rich
plasma
3h deposition
(continuous)
3h deposition + 1h
placing in plasma
without deposition
t(nm)
n 1.95eV
236 1.76
236 1.76
Table 3.7:
samples.
Role of hydrogen plasma on the growth of reactively co-sputtered SRSO
tel-00916300, version 1 - 10 Dec 2013
During multilayer fabrication we expect to alternate between hydrogen-rich plasma
(Ar+H 2 ) and pure Ar plasma. Hence the residual hydrogen in the plasma might
etch the next forming sublayers. Therefore, this study was made to get a deeper
insight on the role of hydrogen plasma on the material growth. Table 3.7 shows the
thickness and refractive index obtained on two samples: (i) SRSO layer deposited
during 3h, and (ii) SRSO layer placed 1h in Ar+H 2 plasma after 3h deposition.
It can be seen that there is no change in the thickness or the refractive index
of the samples after 3h continuous deposition or 3h deposition + 1h placing in
the hydrogen plasma without deposition. This implies that the hydrogen does not
participate in etching if Si and SiO 2 cathodes are closed, and plays a role on the
material growth only if the deposition process is ongoing. The latter was conrmed
by observing an increase in refractive index (1.82) and thickness (308 nm) when
3h deposited SRSO is placed 1h in plasma activating the Si cathode (i.e) deposited
for an additional 1h. Therefore, during the multilayer growth it is wise to allow
sucient time to evacuate hydrogen before the deposition of next sublayer since Si
cathode is active (open) during both SRSO and SiO 2 sublayer growth.
3.7 SRSO-P15 in a multilayer system: SRSO/SiO 2
The goal behind fabricating SRSO/SiO 2 multilayer conguration is to control the
size and density of the Si-np within SRSO layer in accordance with the quantum
connement eect. PL measurements are indicative of the presence of Si-np (exciton)
which are required for desirable absorption and carrier generation in a third
generation PV device. Reducing the Si excess to attain smaller crystals signicantly
decreases the Si-np density in a monolayer. But in a multilayer (ML), the SRSO
sublayer thickness controls the Si-np size without reducing their density and the
SiO 2 barrier between the two consecutive SRSO sublayers prevent the overgrowth of
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