Blue shift of photoluminescence spectrum of porous silicon by helium ion irradiation

Effects of helium ion irradiation on photoluminescence spectrum of porous silicon were investigated. Photoluminescence spectra were measured for silicon prepared by only anodization (porous silicon), by only helium ion irradiation, and by helium ion irradiation before or after anodization. The porous silicon prepared only by anodization showed a photoluminescence spectrum with a peak intensity at 650 nm. The silicon prepared only by helium ion irradiation had no photoluminescence. Silicon prepared by helium ion irradiation followed by anodization showed a blue shift in the photoluminescence spectrum. The blue shift increased as a fluence of helium ion although the intensity decreased. The present blue shift is due to change of silicon nanocrystal structure at the surface. (C) 2002 Elsevier Science Ltd. All rights reserved.