New Type Of Zno-based Transparent Conductive Oxide Thin Films

Transparent conductive oxide films of both ZnO:Mo (ZMO) and ZnO:W (ZWO) have been successfully fabricated by using DC reactive magnetron sputtering from metallic targets of Zn/Mo and Zn/W, respectively. The dependence of electrical, optical and structure properties of both ZMO and ZWO films on deposition parameters, such as Mo-doping content, oxygen partial pressure, and substrate temperature, have been investigated in detail. The structure, surface morphology, chemical state properties, terahertz transmission of ZMO films were studied by XRD, AFM, XPS and terahertz spectroscopy, respectively.ZMO transparent conductive thin films prepared by DC reactive magnetron sputtering on glass substrates from metallic targets were polycrystalline with the hexagonal crystal structure. The experimental condition of DC magnetron sputtering for ZMO films with good optical and electric properties has been established. The minimum resistivity of 7.9×10-4Ω·cm is obtained, with a carrier mobility of 27.3 cm2V-1s-1 and a carrier concentration of 3.1×1020 cm-3, and the average transmittance is about 85% in the visible light region. The refractive index and extinction coefficient at the wavelength of 550 nm are 1.853 and 7.0×10-3, respectively. The results show that oxygen partial pressure greatly effects on the photoelectricity of ZMO thin films, and the carrier concentrationgs of the films could be adjusted by controlling the oxygen partial pressure. The energy bands increase from 3.37 eV to 3.8 eV with the carrier concentrations augment and the carrier effective mass m* is 0.33 times as the electron mass.With DC reactive magnetron sputtering method, transparent conducting molybdenum-doped ZnO thin films with different carrier concentration on glass substrate were fabricated by monitoring oxygen partial pressure. The dielectric responses of the ZMO films are characterized with terahertz time-domain spectroscopy. Frequency dependent conductivity, power absorption, and refractive index are obtained, and the experimental results can be well reproduced with classic Drude model. Our results reveal that, by adjusting the carrier concentration of ZMO film, the conducting ZMO film can serve as broadband antireflection coatings for substrates and optics in terahertz frequency range.ZWO films have been also successfully fabricated firstly by using DC reactive magnetron sputtering from metallic targets of Zn/W. ZWO films are polycrystalline with the hexagonal crystal structure. The lowest electrical resistivity of ZWO films was 6×10-3Ω·cm and the average visible transmittance of the ZWO film was 86%. The results show that electrical, optical and structure properties of ZWO films depend on sputtering parameters such as oxygen partial pressure, doping content, substrate temperature and sputtering current, etc.