Structural and optical characterization of nanostructured undoped CuO and cobalt - doped CuO thin films

The undoped CuO and CuO:Co films are grown using spray pyrolysis technique(SPT). The deposited films undergo a clear morphological change due to an increase in Cobalt dopant from 0 to 4 %. The predominant peak was (200) plane has been confirmed by Xray diffraction. Maximum crystalline size was at the (CuO: 4% Co) film, and the strain decreases from 2.98 to 2.59. Study of the morphology specifies the presence of homogeneous grains, these grains were not homogeneous and had different sizes by adding Co atom. AFM images a reduction in roughness from (7.06 to 3.64) nm. The crystallite size was in the area of 41.35 nm to 32.46 nm as calculated by Scherrer’s formula. The average transmittance values for the films were (77, 74 and 71) % for Undoped CuO, CuO: 2% Co and CuO: 4% Co respectively. The optical energy gaps of the films were calculated. the absorption coefficient increased with an increase at 2% or 4% Cobalt dopant, the band gap of Undoped CuO sample was 2.12 eV, and then decreased slightly with Cobalt content to become 2.04 eV for CuO: 2% Co and 2.04 eV for CuO: 4% Co. also The refractive index and extinction coefficient increased via Cobalt contents.