SELENIUM NANOPARTICLES FORMED BY ION-IMPLANTATION INTO FUSED-SILICA

Selenium ions were implanted into fused silica hosts at an energy of 3 30 keV at fluences of 1 x 10(16), 3 x 10(16), 6 x 10(16) and 1 x 10(17 ) ions/cm(2). The samples containing 1 x 10(17) ions/cm(2) were anneal ed at 600, 800 and 1000 degrees C for 1 h in a 5% H-2 + 95% Ar atmosph ere. The electronic spectra of the as-implanted sample exhibited an ab sorption edge near 2.5 eV (550 nm) as compared to 1.95 for bulk trigon al or amorphous selenium. The absorption edge is shifted to the red as the samples were annealed at increasing temperatures. Infrared reflec tion measurements revealed a decrease in the reflectivity of a peak as sociated with the LO mode silica and is attributed to ion beam damage. A new peak was also observed near 1050 cm(-1) for the as-implanted sa mple and is assigned to an Si-O-dangling bond vibration formed during ion implantation. This peak vanishes when the samples are annealed at 1000 degrees C indicating that the Si-O-Si linkages have reformed. A r edshift of the absorption edge that increases with ion dose and anneal ing temperature observed in the electronic spectra is attributed to qu antum confinement of the photo-generated exciton. This observation is consistent with current models predicting quantum size effects in semi conductor nanocrystals. (C) 1998 Published by Elsevier Science B.V. Al l rights reserved.