A comparative investigation on growth, nanostructure and electrical properties of copper oxide thin films as a function of annealing conditions

This paper is an attempt to compare the influence of various annealing conditions on growth, nanostructure, surface morphology and electrical properties of copper oxide thin films. Cu thin films of 85 nm thickness were deposited on glass substrate by thermal evaporation method, and then post-annealed at different environments (air and oxygen flow), different temperatures (200-400 degrees C) and different times (35 and 75 min). X-ray diffraction results showed (Cu2O) cuprite phase for all annealed samples at 200 and 250 degrees C and (CuO) tenorite phase for all samples annealed under different conditions at 350 and 400 degrees C. A complex phase of CuO and Cu2O was observed for all annealed samples at 300 degrees C, with exception for the sample annealed with flow of oxygen for 75 min. The atomic force microscopy results showed that surface morphology of the samples was strongly affected by the changes of annealing conditions (i.e., time, temperature and environment). The size of the grains increased with annealing temperature and time, while the samples annealed with oxygen flow showed larger grains than those annealed in air. Two different behaviors with annealing temperature were distinguished for the surface roughness of the samples annealed in the air and those annealed with flow of oxygen. Resistivity and Hall effect of samples were measured by a four-point probe instrument and a Hall effect investigation system, respectively. The electrical analyses showed that the variations in annealing conditions had a remarkable effect on measured electrical parameters, namely films resistivity, carriers concentration and type, and Hall mobility.