Intermediate phase silicon structure induced enhancement of photoluminescence from thermal annealed a-Si/SiO₂multilayers

a-Si/SiO2 multilayers with different a-Si sublayer thicknesses were prepared by plasma enhanced chemical vapour deposition (PECVD). An intermediate phase silicon structure (IPSS), which is intermediate in order between the continuous random network amorphous phase and the well ordered crystalline phase, was discovered in the a-Si sublayers near the crystallization onset temperatures through Raman scattering and cross-section high resolution transmission electron microscopy (HRTEM). A strong broad photoluminescence (PL) band, consisting of two peaks centred at 773 nm and 863 nm respectively, was observed with the formation of the IPSS. Based on the analysis of the temperature dependence of PL, the strong PL emission bands centred at 863 and 773 nm are ascribed to the structural defects inside the IPSS and Si = O at the surface of the IPSS, respectively.