REDUCTION OF ION-BEAM-INDUCED AND ATMOSPHERIC AGING OF POROUS SILICONUSING AL AND SIO2 CAPS

Ion bean analysis data are presented on both freshly prepared and 'age d' porous silicon layers of widely varying (10-85%) porosity. Both eva porated Al and PECVD SiO2 surface capping layers are shown to suppress some of the rapid ion beam induced changes in chemical composition th at have been reported during analysis of uncapped layers. Specifically , these capping layers were successful in eliminating carbon and oxyge n accumulation within the material but they only slightly reduced hydr ogen loss under ion bombardment. Evaporated aluminium surface capping layers were partially successful in suppressing long term ambient oxyg en pick-up.