The origin of white luminescence from silicon oxycarbide thin films

Silicon oxycarbide (SiCxOy) is a promising material for achieving strong room-temperature white luminescence. The present work investigated the mechanisms for light emission in the visible/ultraviolet range (1.5-4.0 eV) from chemical vapor deposited amorphous SiCxOy thin films, using a combination of optical characterizations and electron paramagnetic resonance (EPR) measurements. Photoluminescence (PL) and EPR studies of samples, with and without post-deposition passivation in an oxygen and forming gas (H-2 5 at.% and N-2 95 at. %) ambient, ruled out typical structural defects in oxides, e.g., Si-related neutral oxygen vacancies or non-bridging oxygen hole centers, as the dominant mechanism for white luminescence from SiCxOy. The observed intense white luminescence (red, green, and blue emission) is believed to arise from the generation of photo-carriers by optical absorption through C-Si-O related electronic transitions, and the recombination of such carriers between bands and/or at band tail states. This assertion is based on the realization that the PL intensity dramatically increased at an excitation energy coinciding with the E-04 band gaps of the material, as well as by the observed correlation between the Si-O-C bond density and the PL intensity. An additional mechanism for the existence of a blue component of the white emission is also discussed.status: publishe