The thermo-optic effect of Si nanocrystals in silicon-rich silicon oxidethin films

Abstract

The thermo-optic effect of Si nanocrystals in silicon-rich silicon oxide (SRSO) thin films at 1530nm is investigated. SRSO thin films, which consist of nanocrystal Si (nc-Si) embedded inside the SiO2 matrix, were prepared by electron-cyclotron-resonance plasma-enhanced chemical vapor deposition of SiH4 and O2 followed by a 30min anneal at 1150°C. The refractive indices of all SRSO films increased with increasing temperature, with the thermo-optic coefficient increasing from 1.0to6.6×10−5K−1 as the Si content is increased from 37to45at.%. The thermo-optic coeffecients of nc-Si, obtained by correcting for the volume fraction of nc-Si, also increased with increasing Si content from 1to2.5×10−4K−1. The results indicate that the thermo-optic effect of nc-Si is size-dependent, and that it must be taken into account when interpreting the luminescence data from SRSO films with high density of nc-Si.