Photoluminescence and ultraviolet lasing of polycrystalline ZnO thin films prepared by the oxidation of the metallic Zn

We report a simple method for preparing polycrystalline ZnO thin films with good luminescent properties: the oxidization of metallic Zn films. In photoluminescence (PL) studies at room temperature for wavelengths between 370 and 675 nm, we have observed a single exciton peak around 390 nm without any deep-level emission and a small PL full width at half maximum (23 meV), indicating that the concentrations of the defects responsible for the deep-level emissions are negligible. We have also observed optically pumped lasing action in these films. The threshold intensity for lasing was similar to 9 MW/cm(2). (C) 1999 American Institute of Physics. [S0003-6951(99)03444-0].