Fabrication and optical properties of highly ordered ZnO nanodot arrays

We report on the successful fabrication of highly ordered ZnO nanodots on Si(0 0 1) substrates under a low-cost and industrialized technique combining self-organized porous alumina membranes (PAMs) with reactive electron beam evaporation. Scanning electron microscope images reveal the copy of the ZnO nanodot arrays from the PAM masks without the aid of catalysts. In addition to the demonstration of ZnO crystallinity by transmission electron microscopy and micro-Raman measurements, temperature-dependent photoluminescence spectra of ZnO nanodot arrays show high intensity ratio of 400 between the ultraviolet and visible emission due to the low oxygen vacancies (resulting from the oxygen-full growth atmosphere and large surface-to-volume ratio in nanodots). The present technique provides the possibility of realizing good quality ZnO nanodot arrays on different substrates with tunable sizes and morphology.