Electrical and optical properties of undoped and In-doped ZnO thin films

Transparent conducting undoped and indium-doped zinc oxide (ZnO) thin films have been deposited by the spray pyrolysis method at 350 degrees C substrate temperature. X-ray diffraction spectra of the films have shown that the films are polycrystalline and hexagonal wurtzite in structure. The average optical transmittance of 1% indium-doped ZnO thin films was over 84% in the visible range. The direct band gap value of the undoped ZnO film was calculated. Electrical conductivity measurement of Ag-ZnO:In-Ag structures have been carried out using the two-probe method in dark, in the range of temperature from 90 to 320 K. The conductivity of undoped and indium-doped ZnO films increases with increase in temperature. The incorporation of indium in the ZnO film enhanced the conductivity. The conductivity of 1 at.% In-doped film is higher than undoped ZnO at room temperature. The activation energies E, values in the range of 90-320 K temperatures were also determined. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.