Photoluminescence and Optical Properties of CuO Thin Films Deposited via Spray Pyrolysis: Influence of Substrate

CuO thin films were spray-deposited onto a glass substrate and the deposition temperature was varied from 450 to 550° C with 25° C steps. The 450° C deposition temperature was found to be the optimum condition for crystal growth. However, the FESEM images revealed that the grain size increases with raising the deposition temperature. To investigate the optical properties, the transmittance and reflectance data of the resulting films were recorded, and their optical constants, including absorption coefficient, band gap, Urbach energy, refractive index, extinction coefficient, and real and imaginary parts of the dielectric constant were calculated. All the prepared CuO thin films exhibited band gap values around 2.00 eV, which slightly declined with increasing the substrate temperature. The general trend of real and imaginary parts of the dielectric constant was increment and decrement, respectively, with increasing the substrate temperature. The spray deposited CuO thin films were also excited at 486 nm, and the resulting photoluminescence (PL) spectra were recorded at room temperature. Three main and three shoulder peak emissions were detected in the recorded PL of all CuO thin films. The lowest peak intensity was related to the CuOthin film deposited at 500° C.