COMPOSITIONAL VARIATIONS OF POROUS SILICON LAYERS PRIOR TO AND DURINGION-BEAM ANALYSES

The suitability of ion-beam-analysis techniques in quantifying the com position of mesoporous silicon nanostructures has been critically exam ined using films of moderate porosity (55%) prepared on n+ substrates. The effects of room-temperature aging of as-etched and thermally oxid ized porous silicon, the oxidation conditions chosen to render the mat erial luminescent, have been carefully monitored, as have the effects of both ion-beam irradiation and storage of samples in vacuo. It is sh own that the concentrations of the three major impurities oxygen, carb on, and hydrogen can be appreciably altered during analyses, thereby l imiting the reliability of the techniques, as conventionally applied t o porous silicon. The use of appropriate capping layers, which should alleviate the problem, is recommended.