Visible photoluminescence from evaporated SiO_x thin films

SiO_x thin films were prepared by thermal evaporation of SiO powder in vacuum onto Si substrates. The as-deposited samples exhibited blue emission under UV irradiation. Post-annealing was carried out in vacuum, and the photoluminescence (PL) spectra were redshifted from the visible to near-infrared range as the annealing temperature increases. It was also found that the main PL peak wavelength was affected by the deposition rate. The PL spectra of the films consisted of a red and a blue PL. Annealing treatments in oxygen atmosphere were also carried out to investigate the effect of oxidation. From the analysis of the results of infrared spectrometry, we attributed the blue emission to oxygen vacancies in SiO_x. And the red PL could be explained by the quantum confinement effect in Si clusters embedded in the SiO_x matrix.