Optical properties and UV photoresponse of Na^sub 2x^Zn^sub 1-x^O thin film

Na2xZn1-xO thin films were successfully synthesized on quartz glass substrates by sol-gel method. The effect of Na content on the microstructure, optical properties and UV photoresponse of the thin films was investigated using X-ray diffraction, optical absorbance, photoluminescence, and conductivity measurements. The results indicate that the Na0.04Zn0.98O thin film exhibits the strongest preferential c-axis orientation with a polycrystalline hexagonal wurtzite structure and has the largest optical band gap. An obvious decrease in crystal size has been observed with the increasing of Na content. A weak ultraviolet emission band at about 381 nm and a strong visible emission band have been observed in the photoluminescence spectra. The Na0.04Zn0.98O thin film has the shortest growth and decay time (45 and 18 s, respectively) and the largest photoresponse. The results indicate that the photoresponse can be effectively improved by means of moderate Na doping.