Tuning of the physical properties by various transition metal doping in Co3O4: TM (TM = Ni, Mn, Cu) thin films: A comparative study

Abstract This paper presents the results of an experimental work devoted to the synthesis and the characterization of cobalt oxide (Co 3 O 4 ) thin layers doped with transition metal (TM = Ni, Mn, Cu) in order to investigate their structural, optical and electrical properties. The materials were synthesized by the sol–gel method and deposited by dip-coating process. The synthesized samples were characterised by Ultraviolet-visible spectroscopy (UV–visible), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and Complex impedance spectroscopy to elucidate the optical, structural, vibrational and electrical properties. Our structural results show that the materials kept their cubic spinelle structure with preferred orientation of (311), Our optical results show that the transmittance of all doped samples decreases compared to undoped Co 3 O 4 and the doping leads to a reduction of their band gap energies. The complementary phase information is provided by FT-IR spectroscopy. FT-IR spectra of TM-doped Co 3 O 4 confirms the presence of Co 2+ − O and Co 3+ − O vibrations in the spinel lattice. The Nyquist plots suggest that the equivalent circuits (parallel circuit of Rp and Cp) of our films are not qualitatively affected by the doping, but it was found that the effective resistance Rp decreases whereas the effective capacitance Cp increases with doping.