High-pressure Ar passivation to enhance the photoluminescence of Si nanocrystals

Abstract

Photoluminescence (PL) enhancement of Si nanocrystals (Si–NCs) embedded in SiO2 matrix by high-pressure (30 bar) Ar passivation at moderately high temperatures has been observed. For the same pressure, time and temperature of passivation, the PL enhancement of Si–NCs for the Ar passivated sample is even larger than that for the regular H2 passivated one. Electron paramagnetic resonance (EPR) measurement shows that high-pressure Ar passivation causes more reduction in density of dangling bonds which are non-radiative recombination centers, than the regular H2 one. Elemental depth profile analysis shows deep diffusion of Ar atoms into the sample after Ar passivation. The depth profile of PL enhancement after Ar passivation correlates properly with the Ar depth distribution. This effect of inert gas passivation also holds for the case of Kr passivation. The mechanism of such an effect could be that Ar atoms inside the sample alter Si dangling bonds into paired Si ones by a kind of annealing process of thermal atomic collision.