Synthesis and photoluminescence of SiOx nanowires and aligned nanocakes for solar cell applications

The growth of SiO_x nanowires and nano-cakes on Au-coated n-type-Silicon (100) substrate via carbothermal evaporation were studied. The standing nanowires were preferred in solar cells to gain more energy. The effects of the Au layer thickness and rapid heating rate on the morphology of obtained SiO_x nanowires were investigated. A broad emission band from 290 to 600 nm is observed in the photoluminescence (PL) spectrum of these nanowires. There are four PL peaks: one blue emission peaks 485 nm (2.56 eV) two green bands centred at 502 nm (2.47 eV) and 524 nm (2.37 eV) for nanocakes and one ultraviolet emission peak at 350 nm (3.54 eV) and a hemisphere curve over the bluish green area taken for SiO_x nanowires. These emissions may be related to the various oxygen defects and twofold coordinated silicon lone pair centres.