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

tel-00916300, version 1 - 10 Dec 2013
After annealing, SRSO forms Si
nanocrystals due to phase separation
as seen from the sharp transverse
optical (TO) mode appearing
at 517.6 cm −1 .
It is known that when the Si
crystalline size decreases, the optical
TO mode of Si bulk downshifts
in wavenumber [Ritcher 81, Sui 92].
Hence the observed peak at 517.6
cm −1 that appears on 1h-1100°C annealing
conrms the formation of
Si-nanocrystals. This is accompanied
with a decrease of the amorphous
Si mode at 480 cm −1 .
(c) X-Ray Diraction
Figure 3.12: Raman spectra of SRSO-P15 grown
on fused Si substrate. λ excitation = 532 nm and
laser power density =0.14 MW/cm 2
In order to witness the formation of Si-np, their crystallization with annealing and
to estimate the Si-np size, XRD studies were performed (Fig. 3.13).
It can be seen that the as-grown
sample has a broad band between 20-30°
which starts to peak around 28°. This
conrms again that the as-grown sample
already contains Si-np. With increasing
annealing temperature, the crystalline
phase of Si-np increases as can be seen
by the distinct appearance of (111) peak
corresponding to c-Si at 28.37°. After
1h-1100°C annealing, this peak becomes
sharper and has a FWHM of 1.52°. The
peaks at other orientations (220) and
(311) also show their distinct presence
which occurs only when there is a high
crystalline volume in the material. From
Figure 3.13: XRD spectra of SRSO-P15
grown on Si substrate.
the (111) peak, the average Si-np size is estimated as 5.5nm using the Scherrer formula.
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