Photoluminescence from SiNxOy films deposited by reactive sputtering

Non-stoichiometric silicon nitride films with photoluminescence (PL) properties were synthesized by reactive sputtering from a silicon target. The compositions were obtained quantitatively by Rutherford backscattering spectroscopy (RBS). Thermal annealing was performed to activate the emission centres. The excitation wavelength in the PL measurements was 266 nm and the laser power was kept at 1 mW (irradiance of 0.35 mW mm−2) in all measurements. The values of refractive index were obtained by spectral ellipsometry, confirming the RBS results qualitatively. Transmission electron microscopy measurements showed the presence of α-Si3N4, β-Si3N4 and Si2N2O crystalline structures. PL emission was predominantly from localized levels related to defect sites. An ultraviolet band (3.8 ± 0.1 eV) was observed in the emission from the samples with higher oxygen concentration.