Structure and optical parameters of the system with porous silicon: ellipsometric study

The prmcipal angle-of-incidence and effipticity tgp ofthe light reflected from PS surface are measured in the visible on two samples by spectroellipsometry methods. The dependence of the reflected light intensity in the s-plane and ellipsometric parameters on the angle-of-incidence and photoluminescence spectra excited by a pulsed nitrogen laser are recorded as well. An increase of the photoluminescence intensity in storing the sample in the atmosphere and corresponding change of the chipsometric curves are detected. The obtained evidence indicate the formation of a two-layer structure during electrochemical etching of silicon, the outer layer being transparent and supposedly consisting of silicon compound with nanociystalline silicon residuals, while the inner one being the layer ofporous silicon whose pores are filled with the same compound. Assuming that the compound is silicon dioxide, we have determined the fraction ofsilicon in the outer layer. The layer refraction index and thickness are determined. It is established that the photoluminescence is more intense in the sample regions with thicker outer layer.