Photoluminescence of ZnO thin films deposited at various substrate temperatures

This study investigated surface acoustic wave devices with an Al/ZnO/Si structure for use in ultraviolet sensors. ZnO thin films were fabricated using a reactive radio frequency magnetron sputtering system. The substrate temperature of ZnO thin films can be varied to obtain highly crystalline properties. The surface morphologies and c-axis preferred orientation of the ZnO thin films were determined using scanning electron microscopy and X-ray diffraction. In addition, bright-field images of ZnO crystallization were investigated using a transmission electron microscope. From photoluminescence analysis, four peaks were obtained at 377.8, 384.9, 391.4, and 403.4nm. Interdigital transducers of an aluminum electrode were fabricated on the ZnO/Si structure by using a direct current sputtering system and photolithography, combined with the lift-off method, thereby obtaining a surface acoustic wave device. Finally, frequency responses were measured using a network analyzer, and an illuminating test was adopted for the ultraviolet sensor, using a wavelength of 355nm from a light-emitting diode. The sensitivities of the ultraviolet sensor were also discussed. •The ZnO/Si SAW devices exhibit the Rayleigh and Sezawa modes.•The crystalline of ZnO affects the EHP recombination and generation.•The PL spectrum of ZnO shows Gaussian fitting distributions.•The CTDUV is influenced by SAW types and ZnO film characteristics.