(Dr. Zhuomin Zhang, advisor)
"Spectral Radiative Properties of Thin Films with Rough Surfaces Using Fourier-Transform Infrared Spectrometry"
Thin films are used in many energy conversion applications, such as photodetectors
and solar cells. Accurately predicting the radiative properties of thin films
with rough surfaces is necessary but can be challenging due to the complexity
arising from light scattering and interferences at the microscale. Previous
studies showed that scalar scattering theory could yield reasonable agreement
with certain experiments; however, their applicability to various surface conditions
has not been established. This thesis describes measurements of the spectral
transmittance and reflectance of several thin-film materials (including crystalline
silicon wafers and a polycrystalline diamond film) in the mid-infrared spectral
region (2 – 20 ?m), using a Fourier-transform infrared (FT-IR) spectrometer.
The transmittance and reflectance were calculated using thin-film optics for
the double-side polished samples and scalar scattering theory for the single-side
polished samples. The effect of partial coherence was considered using a fringe
smoothing technique. Good agreement between the predicted and measured radiative
properties has been achieved for double-side polished silicon wafers and for
the diamond film. The disagreement for some single-side polished silicon wafers
may be inherently related to their surface microstructures, as suggested from
surface topographic data and images obtained from surface profilometry and microscopy.
Future research is proposed to investigate the correlation between the detailed
surface characteristics and the conical-conical transmittance and reflectance.