Selenium nanoparticles formed by ion implantation into fused silica

Abstract

Selenium ions were implanted into fused silica hosts at an energy of 330 keV at fluences of 1 × 10 16, 3 × 10 16, 6 × 10 16 and 1 × 10 17 ions/cm 2. The samples containing 1 × 10 17 ions/cm 2 were annealed at 600, 800 and 1000°C for 1 h in a 5% H 2 + 95% Ar atmosphere. The electronic spectra of the as-implanted sample exhibited an absorption edge near 2.5 eV (550 nm) as compared to 1.95 for bulk trigonal or amorphous selenium. The absorption edge is shifted to the red as the samples were annealed at increasing temperatures. Infrared reflection measurements revealed a decrease in the reflectivity of a peak associated 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 sample and is assigned to an Si–O-dangling bond vibration formed during ion implantation. This peak vanishes when the samples are annealed at 1000°C indicating that the Si–O–Si linkages have reformed. A redshift of the absorption edge that increases with ion dose and annealing temperature observed in the electronic spectra is attributed to quantum confinement of the photo-generated exciton. This observation is consistent with current models predicting quantum size effects in semiconductor nanocrystals.