Improvement of crystallite size, band gap, and electrical conductivity in Cu-doped Co₃O₄ thin films prepared by spray pyrolysis

In this study, we synthesized undoped and doped cobalt oxide (Co3O4) thin films at a concentration of 0.2 M, incorporating varying copper doping levels of 2, 4, 6, 8, and 10 wt. % through spray pyrolysis technique (SPT). The present investigation aims to enhance the characteristics of the films, including the crystalline size, band gap energy, and electrical conductivity. X-ray diffraction patterns (XRD) were used to determine the size of the crystalline structures. The findings indicate that incorporating Cu leads to an increase in the crystallite size. The crystal size (D) increased to 40.94 nm after doping with 10 wt.% Cu. Energy-dispersive X-ray (EDX) mapping analysis validated the presence of copper within the Co3O4 thin films. We identified two distinct band gaps from the absorption coefficient measurements: E1 and E2. The band gap energy values ranged from 1.441 to 1.388 eV and from 2.061 to 2.012 eV, depending on the Cu doping concentration. The electrical properties demonstrated a reduction in the Rsheet resistance and an enhancement in the electrical conductivity as the concentration of Cu increased.