Effects of growth temperature on the structural and the optical properties of ZnO thin films on porous silicon grown by using plasma-assisted molecular beam epitaxy

Zinc oxide (ZnO) thin films were grown on Si and porous silicon (PS) at different growth temperatures in the range from 150 to 550 °C by using plasma-assisted molecular beam epitaxy (PA-MBE). The effects of PS and growth temperature on the structural and the optical properties of the ZnO thin films were investigated by using atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL). A higher intensity and a narrower full width at half maximum (FWHM) of the ZnO (002) diffraction peak were observed from the ZnO thin films grown on PS, indicating improved crystal quality. For the ZnO thin films grown on Si, the optical properties were gradually enhanced as the growth temperature was increased. However, the structural and the optical properties of the ZnO thin films grown on PS exhibited the largest improvement at a growth temperature of 350 °C. The structural and the optical properties of the ZnO thin films, compared with the ZnO thin films grown on Si, were improved by introducing PS, and the optimum growth temperature was decreased.