The modification of electric and photoluminescence properties of ZnO thin films induced by laser irradiation

This paper aims to contribute to the understanding of laser irradiation effect on the electric and photoluminescence (PL) properties, surface morphology of ZnO thin films. By optimizing the laser beam quality and optical system, with changing the laser parameters, the carrier concentration and UV PL intensity of ZnO thin films could be increased and modulated in a wide range. At a moderate laser energy density, compared with the as grown ZnO films, the irradiated sample exhibits a series of desirable properties: UV emission is distinctly higher, resistivity is decreased by three orders of magnitude, the surface is flat and smooth, and at the same time, it maintains good epitaxial orientation and wurtzite crystal lattice structure. It is notable that the desirable properties could be obtained in several dozens of seconds. Combined with post annealing treatments and X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), atomic force microscopy, Hall measurement, room temperature UV PL and Raman spectra analysis, possible mechanisms of KrF laser irradiation effect on ZnO thin films are discussed.