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

(a) About photoluminescence from a single kind of emitter in multilayer
conguration
tel-00916300, version 1 - 10 Dec 2013
The position and intensity of the emission peaks with regard to variation in thicknesses
and refractive indices were analyzed, for the case of single kind of emitter in
multilayers. Considering a typical example of a 300 nm lm, the range of total thicknesses
was chosen between 250 to 350 nm in steps of 10 nm for simulations. This
was done to account for the inuence of the possible uncertainity in the thickness
determination, on the emission behaviour. Similarly, considering the uncertainity in
refractive index estimation, the real part n 2 was varied between n 2 ± ∆n for a given
thickness, where ∆n ranges between ±0.05 in steps of 0.01.
Inuence of slight variations in
Figure 5.17:
refractive index, ∆n on emission. ∆n varies between
±0.05 in steps of 0.01. [∆n = 0 corresponds
to n 1.95eV obtained by ellipsometry (here, n 1.95ev =
1.8)].
Figure 5.17 shows the emission
spectra of a multilayer thin lm with
single kind of emitter leading to the
appearance of peak (2) of the experimentally
obtained spectra. The
thickness of the lm is xed as 250
nm, and the inuence of slight variations
in refractive index is analyzed.
The results indicate that even
with a slight variation of refractive index
such as ∆n=±0.01, there is an
inuence on the emission intensity. It
can be seen from this gure, that with
increasing refractive index, there is a
drop in the emission intensity while
the peak position remains xed. This
decrease of the emission intensity may
be attributed to the prole of the pump within the lm since the pump intensity
decreases with increasing refractive indices.
Figure 5.18 shows the inuence of refractive index variation on lms with four
dierent thicknesses ranging between 250 nm to 350 nm.
It is interesting to note that, the emission spectra exhibits a non-monotonous
trend of refractive index inuence, with varying thicknesses. For the case of 270
nm, the observations are similar to those from gure 5.17, while for 300 nm, ∆n has
a negligible change in the emission spectra and for 330 nm, the trend has reversed
from what was observed for thicknesses lower than 300 nm. With further increase of
total thickness to 350 nm, the emission spectra again show negligible variation with
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