Si crystalline growth in SiOx films is observed by annealing the films with thermal plasma jet (TPJ) at a temperature higher than 1440 K with annealing duration ranging from 0.9 to 1.7 ms. The size of surface granular structure abruptly increases from similar to 30 to similar to 800 nm by annealing the films at temperatures higher than 1680 K. From the Raman scattering spectra of such large grains, it is confirmed that they have very high crystallinity with the TO phonon hand width of 6.9 cm(-1) and peak position of 520.3 cm(-1). Large grains of similar to 10 mu m are formed by agglomeration with high temperature annealing. From SiOx films annealed at similar to 1200 K, visible red photoluminescence (PL) was observed at room temperature. The peak PL wavelength of 920 nm suggests the formation of nanocrystalline Si with the size of similar to 5 nm. (c) 2007 Elsevier Ltd. All rights reserved.