Abstract:
Although advanced nonlinear optical techniques have demonstrated high potential
for examining elementary excitations in semiconductors, infrared reflectivity
analysis remains the most quantitative technique because simple theories can
be used to describe the material response to an infrared wavelength excitation.
Line shape analysis, comparatively rare for non-linear optical spectroscopy, can
be carried out to yield quantitative results.
Therefore, our objective in the present thesis is to develop an experimental
approach based on infrared spectroscopy for the characterization of the complex
infrared dielectric function of amorphous thin films grown on a substrate, which
is inaccessible by other means. The proposed approach is based on the analysis of
the infrared reflectivity spectrum of the considered film/substrate using a numerical
technique combining the Fresnel theory and the Kramers-Kronig conversion
theorem.
We used the technique developed to deduce the complex infrared dielectric
function of amorphous silicon carbide thin films deposited on silicon at different
temperatures and pressure levels using the pulsed laser deposition (PLD) growth
technique. The results obtained showed that the growth temperature does not
have a significant effect on the dielectric properties of the amorphous films. However,
the variation in pressure allows a substantial modification of the real and
imaginary parts of the infrared complex dielectric function of the amorphous
silicon carbide film.
We believe that the optical technique developed in this work constitutes a
non-destructive method for the characterization of relevant infrared properties of
amorphous materials, which so far are not clear to materials scientists.
