Structural, optical and cathodoluminescence characteristics of undoped and tin-doped ZnO thin films prepared by spray pyrolysis

Cathodoluminescence (CL) spectroscopy, X-ray diffraction and spectrophotometery have been studied of undoped and tin (Sn)-doped ZnO films prepared by spray pyrolysis (SP) technique of zinc chloride and tin chloride. The luminescence films had a polycrystalline hexagonal wurtzite type structure. At room temperature, the cathodoluminescence (CL) spectra of the undoped and doped ZnO films exhibit the common near ultra-violet (UV) band-gap peak at l=382 nm but they differ as regards their visible emissions. The undoped ZnO emits an intensive blue-green light (L=520 nm) and a red emission (L=672 nm). The presence of tin gives rise to a new light emission corresponding to L=463 nm and the extension of blue-green light typical of the intrinsic behavior of the material. CL imaging of undoped ZnO films show that the luminescence is located at defined sites giving rise to a grain-like structure inherent to the surface morphology. The presence of tin in the material leads to great luminescent spots, attributed to large grain sizes