Influence of Electrochemical Etching Modes under One Stage and Two Stage Formation of Porous Silicon on the Degree of Oxidation of its Surface Layer under Natural Conditions

Abstract

Purpose. In this study, some features of the formation of the multilayer structures in porous silicon were investigated by scanning electron microscopy and X-ray emission spectroscopy. Methods and tesniques. Method of electrochemical etching in hydrofl uoric acid solutions was used for the synthesis of substrates. Multi-layered structures were formed by the change of the current density during electrochemical etching (ECE). The morphology of the samples was studied by scanning electron microscopy (SEM). Phase composition of the samples at the different depth of analysis was investigated by ultrasoft X-ray emission spectroscopy (USXES). Computer simulation of the obtained emission spectra was performed using the spectra of references phases. Results. Multi-layered structures of porous silicon were obtained by the electrochemical etching technique at the step change of the current density in the ECE process. Using the SEM technique, pore sizes and the thickness of the formed porous silicon layers were determined. Analysis of the samples by USXES technique with the following computer simulation enabled an understanding of the regularities in the change of the phase composition for the samples of multi-layered por-Si structures of their formation regimes. Conclusion. Features of formation of the multi-layered por-Si structures at the step changes of the current density in ECE process were established. The morphology and phase composition of the porous layer for both single-layer and multilayer structures differed from the surface to the volume and depended on the regime of formation. This fi nding must be taken into account when creating functional electronics based on por-Si multilayers.

Keywords

• silicon
• porous silicon
• multilayer structures
• electrochemical etching
• x-ray emission spectroscopy.