Electrical, photoelectrical and morphological properties of ZnO nanofiber networks grown on SiO2 and on Si nanowires

zno nanofibre networks (nfns) were grown by vapour transport method on si-based substrates. one type of substrate was sio2 thermally grown on si and another consisted of a si wafer onto which si nanowires (nws) had been grown having au nanoparticles catalysts. the zno-nfn morphology was observed by scanning electron microscopy on samples grown at 600 °c and 720 °c substrate temperature, while an focused ion beam was used to study the zno nfn/si nws/si and zno nfn/sio2 interfaces. photoluminescence, electrical conductance and photoconductance of zno-nfn was studied for the sample grown on sio2. the photoluminescence spectra show strong peaks due to exciton recombination and lattice defects. the zno-nfn presents quasi-persistent photoconductivity effects and ohmic i-v characteristics which become nonlinear and hysteretic as the applied voltage is increased. the electrical conductance as a function of temperature can be described by a modified three dimensional variable hopping model with nanometer-ranged typical hopping distances.