Effect of Cu doping on structural and some optical studies of nano NiO films prepared by sol-gel technique

This research deals with the study of the structural and optical properties of as deposited pure NiO and Cu doped NiO nano films with various compositions (0.01, 0.05, and 0.1 mol %). NiO nano films of 100 nm thick were deposited on ultrasonically cleaned glass substrates by sol-gel spin-coating technique with the spin speed and spin time of 3000 rpm and 30 s, respectively. XRD results indicated that the films are polycrystalline and have cubic structure with a preferred orientation along (111). The average grain sizes of the crystallites estimated from XRD data was found to lie in the range of 19.11-26.21 nm. Data of AFM indicate that the surface of films is smooth. The optical transmittance value of nano NiO film reaches to 94 % in the VIS and NIR regions, while it is value of films deposited with 0.1 mol% Cu reaches to 92% which is important for its applications as window layers in solar cells. The values of optical energy gap of NiO and Cu doping by 0.01, 0.05, and 0. 1 mol % were equal to 3.73, and 3.61, 3.49, and 3.42 eV, respectively. (author)