Low annealing temperature effect on Structural, and optical properties of CuO nanostructure thin films

Abstract

In present work, the modified chemical bath deposition method (CBD) called successive ionic layer adsorption and reaction effective coast method was used for deposited copper oxide CuO nanostructured thin films. Structural, surface texture and optical characteristics of the deposited films were studied as a function of low annealing temperature (150, 200 and 250) °C. X-ray diffraction studies showed that the as-deposited and annealed films exhibited low crystallinity of polycrystalline nature in the monoclinic phase. It is observed a fixed or very little increment of peaks intensity and the crystallinity of the deposited films with the increase of annealing temperature to 250 °C. The lattice constants were calculated and show good agreement with the standard values. The crystallite size was decreased, whereas the dislocation density and the number of crystallites were increased with the increment of annealing temperature. The average grain diameter was increased and the average surface roughness decreased with the increment of annealing temperature. The optical energy gap for the as-deposited film is 1.87eV and increased to (2.03, 2.06 and 2.09) eV with the increment of annealing temperatures. The Urbach tails energy width decreased from 0.91 eV to (0.73, 0.54 and 0.46) eV for as-deposited and annealed films at low temperatures (150, 200 and 250) °C respectively. The low annealing temperatures was used because the deposition process was performs at low temperatures below 100 °C, therefore_it can be concluded that the low annealing temperatures used in this work are not suitable temperatures for the growth of CuO films and it can be above 300 °C to enhance the film crystallinity and formation of CuO phase.