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

It can be seen that there is a signicant emission from the material in the visible
range, contrary to the absence of any emission in SRSO-P15 monolayer. This con-
rms that the absence of emission in a monolayered conguration at this annealing
is due to the loss of quantum connement of carriers. The agglomeration into big
size particles is prevented in the ML leading to this emission. It is interesting to
note that the curve is composed of two peaks, peak (1) and peak (2) at 1.41 eV and
1.53 eV respectively indicating there are more than one type of emitters. We can
attribute the peak at higher energy (1.53 eV) to Si-np whose sizes range between 2-3
nm, which represent more than 50% of Si-np (ref. Fig. 3.18), since the mean size
of our Si-np are only about 2.7 nm and cannot lead to a redshifted emission. Peak
(1) at lower energy (1.41 eV) might be attributed to bigger sized particles that are
formed due to overgrowth at interfaces as observed in APT.
tel-00916300, version 1 - 10 Dec 2013
3.8 Inuence of sublayer thicknesses
In order to further explore the emission properties, the inuence of the SRSO and
the SiO 2 sublayer thicknesses on the formation of Si-np becomes the next subject of
concern. To begin our investigations, ve MLs with dierent thicknesses of SRSO
and SiO 2 sublayers were grown as detailed in table 3.8. The total thickness of the
samples were xed around 500 nm to ensure uniformity in comparison. Since this
part of the study is shared between this thesis and the thesis of M. Roussel 4 , these
sublayer thicknesses were chosen to suit the needs of both.
Notation Patterns t SRSO (nm) t SiO2 (nm) Total thickness (nm)
28(8/10) 28 8 10 504
52(8/1.5) 52 8 1.5 494
36(4/10) 36 4 10 504
70(4/3) 70 4 3 490
90(4/1.5) 90 4 1.5 504
Table 3.8: SRSO/SiO 2 MLs-Sample details
3.8.1 Fourier transform infrared spectroscopy
Typical FTIR spectra of SRSO/SiO 2 ML with annealing is shown in gure 3.20a.
The FTIR analyses were made to witness the evolution of phase separation process
from 1h-900°C to 1h-1100°C (CA). The as-grown spectrum is also included in
4 Groupe de Physique des Matériaux, Université et INSA de Rouen, UMR CNRS 6634, France.
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