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

tel-00916300, version 1 - 10 Dec 2013
Si:Si 3 N 4 interfaces [Maria 75] and/or to various defect states in silicon nitride.
However, these possibilities of dierent
origins of emission will be analysed
and conrmed in the forthcoming sections.
After subjecting to CA, the emission
from SRSO/SRSN ML is quenched
whereas in section 3.7.2 of chapter 3
it was seen that CA process enhances
emission in SRSO/SiO 2 MLs. Since it
was seen from XRD and HR-TEM that
the average size of the nanocrystals in
CA SRSO/SRSN MLs are about 3.8-4
Figure 4.25: PL spectra of as grown and
1h-1100°C (CA) 100(3.5/5) ML.
nm, this quenching of PL cannot be attributed
to the overgrowth of crystals.
These results indicates that SRSN sublayers when annealed at high temperature
show a detrimental eect on the emission from SRSN as well as SRSO sublayers.
(b) Absorption coecient, (α)
The absorption behaviour of the CA 100(3.5/5) MLs were investigated by comparing
α values of other Si-based layers investigated in this thesis (Fig. 4.26).
The absorption coecient curves of reference
a-Si and c-Si are also presented
by using the data from [Internet ta] to
facilitate comparison between the absorption
behaviours of the thin lms.
The absorption coecient curves
are similar in SRSN monolayer and
SRSO/SRSN ML, from energies higher
than 2 eV. It is interesting to note
that the absorption coecient values are
about 10 times higher in SRSO/SRSN
Figure 4.26: Comparison of absorption coecient
curves obtained from CA 100(3.5/5) MLs as compared to the SRSO/SiO 2
ML with other CA Si-based thin lms investigated
in this thesis. The reference absorption
ML, at energies greater than 2.5eV.
Besides, in the range of emission energies
also (typically 1.4-1.7 eV), the
curves of c-Si and a-Si are also plotted for
comparison [Internet ta].
SRSO/SRSN MLs have a higher absorp-
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