Modification of electrical and optical properties of CuO thin films by Ni doping

Abstract

Undoped and Ni-doped CuO thin films were deposited onto glass substrates using a spin-coating technique at different doping concentrations (undoped, 2, 4, 6, and 10 %). X-ray diffraction patterns for undoped and Ni-doped CuO thin films indicated that the films were polycrystalline, with preferential growth in the (002), (111), and (−311) directions. Atomic force microscopy images revealed that the surface morphologies of the films were not uniform. Scanning electron microscopy images confirmed the presence of agglomerated particles on the surfaces; the coverage increased with the doping level. A Hall effect system with a van der Pauw configuration was used to investigate the electrical properties of the CuO films. The free charge carrier concentration decreased and hole mobility increased with increasing Ni concentration, with the exception of the 10 % Ni-doped CuO sample. Ultraviolet–visible spectroscopy measurements of the film samples indicated an average transmittance of 30–40 % in the visible range. The optical band gap decreased slightly for low-level doping and increased from 2.03 to 2.22 eV for 10 % Ni incorporation. The electrical and optical properties of the CuO films were modified by Ni doping, i.e. the band gap decreased and the mobility increased almost linearly, with the exception of the 10 % Ni-doped sample. SEM images of a undoped b 2 % c 4 % d 6 %, and e 10 % Ni-doped CuO thin films.