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

tel-00916300, version 1 - 10 Dec 2013
an energy-selecting slit at the SiO 2 (23 eV) plasmon energy shows the bright and
dark contrast of the SRSO and SRSN sublayers respectively. The image taken at Si
(17eV) plasmon energy reveals the presence of a high density of Si-np (10 13 np/cm 2 )
that are distributed all along the SRSO sublayers. There are no traces of even amorphous
Si-np in SRSN sublayers which may be attributed to either the insucient
Si excess or the STA process which favours Si-np formation only in SRSO sublayers.
However, it is interesting to note that the density of Si-np formed with STA in
SRSO/SRSN MLs are similar to those in SRSO/SiO 2 achieved after a long time CA
process.
Thus, these microstructural and optical investigations indicate that a strong PL
emission can be achieved after STA. The absorption studies after such an annealing
showed that the absorption coecient curves lies between that obtained from asgrown
and CA SRSO/SRSN MLs (not shown here). The STA and the as-grown
sample follow a similar trend with low absorptions for energies lower than 2 eV and
high absorptions for energies greater than 2.5 eV. A balance between emission and
absorption behaviour is obtained from STA SRSO/SRSN MLs which is promising
for device applications at a reduced thermal budget.
4.7 Eect of number of patterns on emission
In order to understand if the number of patterns (i.e. total thickness) of the ML
has an inuence on the emission intensity, three STA SRSO/SRSN MLs with 20, 50
and 100 patterns were compared (Fig. 4.35a).
(a) Pattern number vs. emission intensity.
(b) Curve tting on 50 and 100 patterned ML.
Figure 4.35: Eect of pattern number on the emission of STA SRSO/SRSN MLs.
An increase in the PL intensity is noticed with increasing number of patterns. It
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