Porous silicon stabilization electrochemical oxidation

A number of studies has been attempted to stabilize porous silicon low-temperature oxidation in a controlled way [1-3], surface modification of silicon nanocrystallites by chemical [4] or electrochemical [5] procedures etc. Rapid thermal processing (RTP) is thought to be a shortcut method of the PS stabilization for a number of purposes. However, there is no data about RTP influence on the PS structure. Therefore, the study of lattice deformations of PS layers after RTP is of great interest. In the present work. X-ray double-crystal diffractometry was used to measure lattice deformations of PS after RTP of millisecond and second durations. 

Bsiesy et al. (1991) believe that electrochemical oxidation of PSi has the following advantages (1) electrochemical oxidation of porous silicon can be achieved easily and (2) it is possible to oxidize either the lower part of the porous layer, or the whole depth, at a level which depends on the exchanged charge. This method therefore appears to be more attractive than thermal oxidation when incomplete oxidation is required. In particular, such a requirement appears during silicon (or other material) epitaxy on porous silicon. These processes generally involve temperatures above 400 °C and porous silicon must be stabilized by a preoxidation step in order to conserve its very thin microstructure. If this preoxidation is achieved by thermal oxidation, there is also oxide growth on top of the sample, which must be eliminated before subsequent epitaxy. Electrochemical oxidation, with an appropriate choice of experimental conditions, can lead to oxidation limited to the inner part of the porous layer. 

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