EFFECTS OF SUBSTRATE TEMPERATURE ON THE DOPING CHARACTERISTICS OF Li-W CO-DOPED ZnO FILMS

Li - W co-doped ZnO (LWZO) thin films were deposited on quartz glass substrates by RF magnetron sputtering technology. The properties of LWZO films deposited with varied substrate temperatures were investigated. When the substrate temperature was lower than 120°C — according to X-ray diffraction (XRD) patterns, films keep hexagonal wurtzite structure with the (002) plane as preferred orientation — the optical transmittance was higher than 85%. When the substrate temperature was higher than 120°C, the results of XPS and XRD show that W 6+ will work as donors, and the (101) peak appeared; the optical transmittance decreased slightly but still higher than 82%. Scanning electron microscope (SEM) and its two-dimensional Fourier transform images showed that films had smooth surface and columnar particles structure when the substrate temperature was lower than 120°C. The film surface became rougher and flaky-shaped particles structure could be observed when the substrate temperature was higher than 120°C. In addition, the lowest electrical resistivity of sample was 3.6 × 10-3 Ω ⋅ cm which was obtained at substrate temperature 240°C.