Photoluminescence from Nanoscale Si in a-SiOxMatrix

Abstract

AbstractWe prepared a-SiOx (x < 2.0) films by co-sputtering Si and SiO2 targets and found that these films included nano-scaled a-Si regions in a-SiOx matrix. The structure of the films was evaluated by X-ray photoemission spectroscopy (XPS) and infrared absorption. The XPS spectra in the a-SiOx films showed two Si 2p peaks around 99.6 and 104 eV. This indicates that the a-SiOx films were composed of Si and a-SiO2 regions. The optical gap energy of this system rapidly increased when x exceeded 0.7. The rapid increase in the optical gap of this system indicates the formation of nanometer sized Si islands. The photoluminescence (PL) peak energy of this material decreased with increasing temperature above 60 K when x was less than 0.7. On the other hand, when x exceeds 0.7, the PL peak energy increases with temperature above 60 K. The quenching of PL intensity also takes place at 60 K. These results indicate a film structure change at x = 0.7, and recombination path and carrier distribution changes at 60 K. A correlation between film structure and PL properties are discussed. PL properties in this system are explained by superposition of the PL peak from nanoscale Si and a-SiO2 matrix.