Random and ordered macropore formation in p-type silicon have been studied experimentally. We found that the density of macropores in a random macropore nucleation regime is linearly depending on the samples doping concentration. Macropore etching rate depends linearly on the current density up to the critical current density value; a saturation in the etching rate takes place when this value is exceeded. The so-called proximity effect was discovered for the ordered macropore formation regime. This phenomenon, and large pore diameters and pore wall thickness, and their variations have been observed in the experiments which can be accounted for in the frame of a simple model of the current localization at the pore bottom. An analysis of the experimental data based on the at present time existing theoretical models has been done. This analysis leads to the conclusion that none of these models can describe the existing experimental data including data of this work. It is clear that new experimental data are needed to come to a universal model of the electrochemical macropore formation. © 2001 The Electrochemical Society. All rights reserved.

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Hydrogen separation from gas mixtures and purification are of great importance and interest. Technologies based on the use of metallic membranes are the most suitable ones for these purposes. Pd and its alloys with Ag, Au, Cu and Ni are the best candidates for the membranes. In the present work, technology of the membranes formation based on macroporous silicon with Pd/Ag thin film has been investigated.