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

tting operations show the presence of two peaks centered around 1.4 eV and 1.5
eV in all the CA annealed PL spectra of this material. The second peak around 1.5
eV was explained to be a contribution from Si-np in SRSO sublayers as conrmed
by XRD and APT measurements in chapters 3 and 4, while the origin of peak 1
was interpreted as a contribution from few overgrown Si-np at the interface. It was
also suspected that there may be some optical phenomena such as interference that
aects the shape of the emission spectra. Hence it needs to be conrmed if the two
peaks are a contribution of two kinds of emitters in the material.
tel-00916300, version 1 - 10 Dec 2013
Figure 5.16: Experimentally obtained PL spectra of 50(3/3) SRSO/SiO 2 ML.
Moreover, it was seen in chapter 3 that the emission peak intensity follows a
non-monotonous trend with increasing t SiO2 . Therefore theoretical simulations are
performed on SRSO/SiO 2 MLs to address the two major issues that arise from
experimental observations:
(i) What is the origin of two emission peaks - Geometrical/optical eect or
presence of two types of emitters?
(ii) What is the inuence of t SiO2 on PL intensity ?
5.5.1 Origin of two emission peaks
In order to understand the origin of peaks, PL curve of 50(3/3) ML was simulated
with an initial assumption that only the emission peak at 1.5 eV (peak 1) is from the
Si-np (i.e. only one kind of Si-np distribution). The factors that inuence emission
when there is only a single kind of emitter is investigated which is later extended
to double kind of emitters. Simulations were made by varying thickness, refractive
index, and cross-sections within the range of uncertainity, to compare the shape of
the simulated curves with single and double kind of emitters with experimental PL
curve.
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