The origin of photoluminescence from thin films of silicon-rich silica

We have carried out a study of the photoluminescence properties of silicon-rich silica. A series of films grown using plasma enhanced chemical vapor deposition over a range of growth conditions were annealed under argon at selected temperatures. Photoluminescence spectra were measured for each film at room temperature and for selected films at cryogenic temperatures. The photoluminescence spectra exhibit two bands. Fourier transform infrared and electron spin resonance spectroscopies were used to investigate bonding and defect states within the films. The data obtained strongly suggest the presence of two luminescence mechanisms which exhibit different dependencies on film growth conditions and postprocessing. We make assignments of the two mechanisms as ~1! defect luminescence associated with oxygen vacancies and ~2! radiative recombination of electron-hole pairs confined within nanometer-size silicon clusters ~‘‘quantum confinement’’!. © 1996 American Institute of Physics. @S0021-8979~96!04912-2#