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

tel-00916300, version 1 - 10 Dec 2013
Figure 3.21: Inuence of sublayer thicknesses on Si-np formation. Upper part of the
gure shows the plan view of Si-np in SiO x sublayers in as-grown and CA cases with
regard to sublayer thickness. The bottom part of the gure shows a 3D illustration and
a 3D volumic reconstruction of two specic cases of ML. (The plan view and volumic
reconstructed images are given by M. Roussel from GPM).
as seen in 70(4/3) case (Fig. 3.21). These results conrm that the SiO 2 sublayer
plays a strong role as a barrier layer in the formation of Si-np with controlled sizes.
3.8.3 Photoluminescence
The PL spectra of the samples after CA are shown in gure 3.22. In gure 3.22a the
spectra are as recorded and in gure 3.22b the spectra is normalized to the pattern
number. As mentioned before, all the curves are corrected to spectral response.
It can be seen in both the gures that there is no emission if t SRSO = 8 nm
which is attributed to the overgrowth of Si-np resulting in the loss of quantum
connement. In gure 3.22a it can be noticed that the most intense emission is
obtained from 70(4/3) ML. Considering the MLs with 4 nm thick SRSO sublayers,
we observe the lowest intensity for the highest number of emitters (green curve)
and the highest emission for the intermediate number of emitters (pink curve).
Consequently the number of emitters is not the only necessary parameter to achieve
the highest intensity. This non-monotonous trend must be considered along with
the t SiO2 which may play a role on the emission intensity.
Since the total thickness of these samples are the same, the relevant parameter to
compare the spectra would be to nomalize to one pattern of each ML. Therefore in
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