Annealing Effects on the Properties of Copper Oxide Thin Films Prepared by Chemical Deposition

Copper oxide thin films with thickness of 0.45 mu m were chemically deposited on glass substrates by dipping the microscope glass slide for 20 s each in 1 M NaOH and copper complex solutions. Temperature of NaOH solution was increased to 70 degrees C, while the copper solution was maintained at room temperature. Copper oxide thin films were annealed in air at different temperature of 200 - 400 degrees C and as-prepared sample was used as reference. The films structures were studied by XRD. The patterns showed that the films as prepared and annealed at 200 degrees C were cuprite structure with Cu2O composition. Films annealed at 300 degrees C consist of mixed tenorite (CuO) and cuprite (Cu2O) phases. Annealing the films in air at 400 degrees C completely converts these films to tenorite structure with composition of CuO. The proportion of the two forms of copper oxide varies with oxidation temperature. The surface properties were characterized using scanning electron microscopy. UV-Vis transmittance spectra confirmed the results from the XRD by a shift in the optical band gap from 2.40 to 1.73 eV. The conversion was also confirmed by the FTIR spectroscopy measurement. Photoluminescence intensity is greatly improved with the increase in annealing temperatures.