Optical and structural properties of ZnO/TiO2/ZnO multi-layers prepared via electron beam evaporation

We prepared a ZnO/TiO2/ZnO multi-layer on quartz glass substrate via electron beam evaporation. Optical and structural properties of the ZnO/TiO2/ZnO multi-layer were investigated. The TiO2 buffer layer is found to improve the crystallinity of the ZnO thin film. A green emission of the ZnO thin film deposited on the TiO2 buffer layer was significantly enhanced due to the increased defect concentration of oxygen vacancy. Photoluminesence spectra measured at 9 K revealed that a violet luminescence at 409 nm was attributed to the draft of the donor's defect levels in the ZnO thin film.