Electrical, structural and optical characterization of copper oxide thin films as a function of post annealing temperature

Copper oxide thin films were obtained by annealing (temperature ranging between 100 and 450 °C) the metallic Cu films deposited on glass substrates by e‐beam evaporation. XRD studies confirmed that the cubic Cu phase of the as‐deposited films changes into single cubic Cu2O phase and single monoclinic CuO phase, depending on the annealing conditions. The crystallite size is varied between ∼12 and 31 nm. The lattice parameters of cubic Cu and Cu2O phases are estimated to ∼3.60 and ∼4.26 Å, respectively. The films with Cu2O phase showed p‐type characteristics. The conductivity is decreased linearly with the decreasing temperature (1/T), which has confirmed the semiconductor nature of the deposited films. The calculated activation energy is varied between 0.10 and 0.16 eV. The surface microstructure is changed depending on the variation in the annealing temperature. The poor transmittance of the as‐deposited films (<1%) is increased to a maximum of ∼80% (800 nm) on annealing at 200 °C. The estimated direct allowed band gap is varied between 1.73 and 2.89 eV.