Growth of tenorite thin films and investigation of effects of thermal treatment on their physical properties

In this thesis, tenorite (cupric oxide, CuO) thin films were grown on the glass substrates by reactive radio frequency (RF) magnetron sputtering technique under the different total gas pressures of 10 and 15 mTorr at a constant substrate temperature of 200 oC. The tenorite thin films were annealed in air at different annealing conditions. The effects of total gas pressure, annealing temperature and time on surface morphology, composition, crystal structure and optical properties of films were characterized by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), X-rays Diffraction (XRD) and UV/VIS Spectroscopy. It was seen that the film growth rate and the grain size decreased with the increase of the gas pressure. It was observed that the surface morphology of films changed due to the annealing conditions. SEM images revealed that the surfaces of films are comprised of randomly distributed grains and voids. From XRD studies, it was determined that the copper oxide thin films have not a second phase according to the growth and annealing conditions. EDX results also revealed that the composition and the single CuO phase of the polycrystalline films were not affected by the annealing conditions. All of the films exhibited well-crystallization on the reflection plane. Shifts in the positions of the diffraction peaks were observed due to residual stresses. From the transmittance spectrums, it was determined that the films have a high absorbance of light in the visible and near-infrared regions ranging from 400 nm to 800 nm. The optical band gap (Eg) was found to increase from 2,244 eV to 2,299 eV with increasing gas pressure from 10 mTorr to 15 mTorr. The absorption edge of the films was also found to be shifted towards the lower wavelenght and higher energy as the gas pressure increase. In addition, with effect of thermal treatments, the optical band gap decreased because the absorption edge of films shifted to higher wavelengths.