Optical anisotropy of nanostructured silicon films studied by Fourier transform infrared spectroscopy

Abstract

Electrochemically nanostructured Si films with surface orientation (110) prepared at different current density were investigated by Fourier transform infrared spectroscopy. The spectra exhibit beats of interference fringes arisen from the summation of intensities of ordinary and extraordinary waves which interfere in the film. The investigated films are shown to exhibit properties of a negative uniaxial crystal (n_o > n_e) with optical axis lying in the surface plane along [001] direction. The value of birefringence reaches 18% for nanostructured Si films with porosity of 80%. Experimental data agree with calculations based on the effective media approximation for anisotropically spaced Si nanocrystals.