Electroless deposition of cadmium stannate, zinc oxide, and aluminum-doped zinc oxide films

Abstract

Transparent conducting films of cadmium stannate (Cd2SnO4), zinc oxide, and aluminum-doped zinc oxide have been made by a simple, economical electroless deposition technique. The as-deposited films of cadmium stannate have a 75% transmittance in the visible, 48% reflectance in the IR, and a band gap of 2.7 eV. Its resistivity is ∼10−1 Ω cm. Vacuum annealing changes the transmittance in the visible range to 82%, the IR reflectance to 62%, and the band gap to 3.1 eV. The corresponding values for the hydrogen-annealed films are 87%, 76%, and 3.2 eV. Annealing lowers the resistivity of the films to ∼10−2 and ∼10−3 Ω cm for vacuum and hydrogen-annealed films, respectively. The undoped zinc oxide films have transmittance in the visible and reflectance in the IR of 80 and 67% respectively. Aluminum doping increases the transmittance to 88% and reflectance to 83%. The optical band gap of undoped and aluminum-doped zinc oxide films are found to be 3.40 and 3.98 eV, respectively. The resistivity is 1.20×10−2 and 6.0×10−2 Ω cm for undoped and aluminum-doped ZnO films. Vacuum annealing reduces the resistivity of the films to 2.5×10−3 and 2.1×10−4 Ω cm for undoped and aluminum-doped ZnO films, respectively.