Harnessing the tunability of intrinsic defects in isovalent Zn doped spray deposited CuO thin films

Abstract

Doping is a versatile tool for tailoring the properties of semiconductor thin films. This article investigates the influence of isovalent dopant, Zinc (Zn), on the electronic, optical and structural characteristics of copper oxide (CuO) thin films prepared by spray pyrolysis technique. Structural characterization from XRD and Raman studies confirms the successful incorporation of Zn atoms into the CuO lattice without altering monoclinic structure of the films. The absence of secondary phases like Cu2O and ZnO confirms the good quality of the prepared films. A significant variation in the morphology of the films was observed in FESEM images. The EDS analysis confirmed the incorporation of Zn atoms in CuO films and showed that the prepared films are oxygen rich in nature. The band gap of the films increased from 1.50 eV in pristine samples to 1.62 eV in 8 at% Zn-doped sample. Different defect related emissions were observed in PL spectra with the resultant emission in yellowish green region as obtained from chromaticity diagram. XPS analysis confirmed that both Cu and Zn are found in +2 oxidation state. The electrical conductivity and carrier concentration of CuO films improved with doping due to the enhanced oxygen interstitial defects. The carrier density increased from 2.17 × 1014 to 2.82 × 1015 cm−3 after 6 at %doping with the lowest resistivity of 708 Ω cm. Hence, the properties of CuO films can be effectively modified by Zn doping. Zn doping improved the electrical properties of the films without trading off the excellent optical properties of CuO thin films making them suitable in solar cell absorber layer applications.