Fabrication Of Sb-doped ZnO Thin Films And Their Optical Properties

As a new type of wide band gap oxide semiconductor materials,ZnO thin films has excellent optical and electrical properties. It has wide range applications, such as light-emitting devices,surface acoustic wave devices,gas sensors,transparent conductive thin films, etc. The band gap of ZnO thin films is 3.37eV at room temperature, the exciton binding energy of ZnO is 60 meV, which is much higher than ZnSe and GaN wide-band gap semiconductor materials. ZnO thin films can be prepared at temperature lower than 500℃and its raw materials is easy to get , non-toxic, low cost. Owing to these properties, ZnO has become a kind of bright application prospects for short-wavelength light-emitting materials. Meanwhile, with the const research of light-emitting properties of ZnO,different wavelengths of bule-green emission have been reported, which has the important meaning to develop blue-green photoelectron devices.In this paper, the ZnO/ZnO:Sb thin films were prepared on glass substrate by RF reactive magnetron sputtering. The metal Zn and Zn-Sb alloy were used as target materials and the high pure oxygen and argon were used as sputtering gas. The thin film samples annealed in the atmosphere of high-purity nitrogen at 450℃,550℃for one hour. The thickness,structure,optical properties of ZnO/ZnO:Sb films are investigated by step apparatus, x-ray diffraction(XRD), double beam UV-visible spectrophotometer, fluorescence spectrophotometer.The samples'x-ray diffraction spectra showed that ZnO thin films is single crystal growing along the C-axis preferred orientation and ZnO:Sb films mainly grow along the ZnO(002) direction. The ZnO:Sb films'crystal plane spacing is larger than ZnO films'when depositing in the environment of low oxygen concentration and high oxygen concentration ,mainly because of substituting Sb+3 for Zn+2 caused the lattice expansion. No impurity phases are detected. The optical band gap of ZnO/ZnO:Sb films increase with the increasing of oxygen concentration and decrease after anneal in nitrogen. Comparing the optical band gap of ZnO/ZnO:Sb films which prepared under the same conditions, the latter's band gap is smaller, which is due to impurity levels. The room temperature emission spectrum of the K series ZnO and P series ZnO:Sb films both presented a wide band Blu-ray peak, which the central wave length located at about 467nm. The broadband Blu-ray peak is composed of four different blue emission peaks. The room temperature emission spectrum of S series ZnO:Sb films presented two strong blue emission peaks,which located about 423nm and 486nm,respectively. When the excitation wavelength is 360nm,the intensity of 486nm Blu-ray peak is greatly enhanced. We analysed the luminescence mechanism of the blue peaks:the blue emission of 467nm comes from the electron transition from the oxygen vacancy(VO)level to the oxygen interstice(Oi)level. The blue emission peaks of 423nm come from the electron transition from the shallow donor level which zinc interstice(Zni)forms in the ZnO:Sb films to the valence band. The blue emission peaks of 486nm come from the electron transition from the donor level which zinc interstice(Zni)forms to the acceptor level of zinc vacancy(VZn)and relate to the corresponding blue center which the Sb+3 ions provide with. The emergence of Blu-ray peaks have great significance for the development of a monochromatic blue light-emitting devices.