Mechanism of photoexcitation of oxide-related emission bands in Si–SiO2 systems

The excitation process of oxide-related centers in magnetron sputtered Si–SiO2 systems with Si nanocrystals of different sizes is investigated by photoluminescence, EPR and Raman scattering methods. It is found that the photoluminescence spectra of the systems studied contain four bands. The infrared band (1.38–1.54 eV) can be ascribed to exciton recombination in Si crystallites, while the other bands (at 1.7, 2.06 and 2.32 eV) can be attributed to oxide-related defects. Besides intra-defect transitions, the excitation of oxide defects due to light absorption in Si crystallites was found. It is shown that the effectiveness of this excitation channel decreases with the increase of Si crystallite sizes. The mechanism of excitation of oxide-related centers via an Auger process with bound carrier participation is discussed.