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

(a) Absorption coecient curves.
(b) PL spectra.
Figure 4.7: The absorption coecient and photoluminescence spectra obtained from
SRSN samples, with regard to refractive index and annealing.
tel-00916300, version 1 - 10 Dec 2013
grown samples (80-100 nm thick) with three dierent compositions (refractive indices
2.012, 2.44 and 3.3 that are close to Si 3 N 4 , SRSN and Si respectively). The left part
of gure 4.7a shows that the absorption increases with increasing Si excess, which
can be attributed to the higher density of Si-np formed in the material.
Figure 4.8: Optical investigations on SiN x
monolayers with n 1.95eV between 2.01 and 2.13.
seen from gure 4.7b.
Comparing the SRSN samples
with same refractive index in the
left and right part of this graph,
it is interesting to note that with
increasing thickness the absorption
coecient of the material is lower,
whatever be the annealing treatment.
This dierence cannot be explained
at the moment. However
the absorption does not vary with
annealing for energies higher than 3
eV.
In the case of PL properties,
both the thin and thick SRSN samples
(n 1.95eV =2.44) do not exhibit
any emission in their as grown or annealed
state whatever the temperature
or time of annealing as can be
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