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 °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_a values in the range of 90‐320 K temperatures were also determined. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)