Optical anisotropy in thermally evaporated a-Ge0.95Sn0.05Se2 columnar thin films

Optical anisotropy (OA) was found using a differential polarized optical transmission technique on a-Ge0.95Sn0.05Se2 thin (<1.5 μm) columnar morphology films deposited by thermal evaporation at various angles on mica substrates. Low incident power (0.9 mW), sub-bandgap (633 nm) polarized light was used. By estimating an upper limit, we found that differential absorption alone cannot account for the observed OA. Assuming a simple uniaxial birefringent model, a linear dependence of the difference in effective refractive indices on the sine of the column inclination was found. These results are also compared with earlier OA observations in pulsed laser deposited a-GeSe2 thin films.