Optical properties of Si nanocrystals in SiO2 matrix synthesized by reactive pulsed laser deposition

Abstract

Si ion implantation into SiO2 is widely used to synthesize specimens of SiO2 containing supersaturated Si. We also prepared specimens of supersaturated Si in SiO2 by reactive pulsed laser deposition (PLD) in an oxygen atmosphere. After high temperature annealing of these specimens induces the formation of embedded luminescent Si nanocrystals in SiO2. In this work, the potentialities of excimer UV-light (172 nm, 7.2 eV) irradiation and rapid thermal annealing (RTA) to enhance the photoluminescence and to achieve low temperature formation of Si nanocrystals have been investigated. The Si ions were introduced at acceleration energy of 180 keV to fluence of 7.5 x 1016 ions/cm2. We also prepared Si nanocrystals embedded in a SiO2 by reactive pulsed laser deposition (PLD) in an oxygen atmosphere by using conventional PLD system with 2nd-harmonic YAG laser (532 nm, 10 Hz, 80 J/cm2) under controlled low oxygen pressure. Samples were subsequently irradiated with an excimer-UV lamp. After the process, the samples were rapidly thermal annealed before furnace annealing (FA). Photoluminescence spectra were measured at various stages at the process. We found that the luminescence intensity is enhanced with excimer-UV irradiation and RTA. Moreover, effective visible photoluminescence is found to be observed even after FA below the annealing temperature at 1000 °C, only for specimens treated with excimer-UV lamp and RTA. We will make clear the similarities of photoluminescence with the way of preparation techniques.