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

The thermo-optic effect of Si nanocrystals in silicon-rich silicon oxide (SRSO) thin films at 1530 nm 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 30 min anneal at 1150 °C. The refractive indices of all SRSO films increased with increasing temperature, with the thermo-optic coefficient increasing from 1.0 to 6.6310−5 K−1 as the Si content is increased from 37 to 45 at. %. The thermo-optic coeffecients of nc-Si, obtained by correcting for the volume fraction of nc-Si, also increased with increasing Si content from 1 to 2.5310−4 K−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. © 2004 American Institute of Physics. [DOI: 10.1063/1.1798395]