Heat-treatment effects on porous silicon

High-resolution scanning electron microscopy of porous silicon (PS) subjected to various annealing treatments in vacuum has revealed a spheroidal particlelike structure that only becomes clearly apparent after treatment at about 250 °C. This is consistent with recent suggestions that any quantum effects arise from particles. It is deduced that the particles have a coating that is reduced or removed on heating. The concomitant effects on the current-voltage curves of PS, caused by annealing and also by prolonged air exposure, have been measured, and are consistent with the interpretation.