Enhanced UV-vis photoconductivity and photoluminescence by doping of samarium in ZnO nanostructures synthesized by solid state reaction method

In the present work, polycrystalline undoped and samarium doped zinc oxide (ZnO) nanostructures were successfully synthesized by solid state reaction method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-vis absorption spectroscopy, photoluminescence study and photoconductivity study. XRD patterns revels that the samples possess hexagonal wurtzite structure of ZnO without any secondary phase after samarium doping. The crystallite size is calculated by Debye-Scherer's formula. Williamson-Hall analysis reveals presence of strain in synthesized samples. SEM micrographs show spherical and oblate type shape of nanoparticles. UV-vis absorption study shows blue shift in absorption band edge in undoped as well as in samarium doped ZnO nanoparticles as compared to its bulk counterpart. Photoluminescence spectra of the samples show peaks corresponding to near band edge UV emission and defect related emissions in the visible region. In photoconductivity study, enhancement of photosensitivity has been observed in 1% Sm-doped ZnO sample while the maximum photocurrent is found in 3% Sm-doped sample. The variation of dark current and photocurrent with applied voltage exhibits super-linear nature. The rise and decay of photocurrent indicate anomalous behavior during steady state illumination.