Characterization of Mn-Doped Co3O4 Thin Films Prepared by Sol Gel-Based Dip-Coating Process

Abstract

Abstract In this article, manganese-doped cobalt oxide (Mn-doped Co3O4) thin films have been prepared on glass substrates using sol gel-based dip-coating technique in order to investigate their optical, structural and electrical properties. The Mn concentration was changed from 0 % to 9 %. The synthesized samples were characterized by ultraviolet-visible spectroscopy (UV-visible), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and complex impedance spectroscopy to elucidate the optical, structural, vibrational and electrical properties. Our optical results show that the transmittance of Mn-doped Co3O4 films decreases with increasing doping levels. The optical band gaps were found to be ( E g 1 = 1.51   e V , E g 2 = 2.12 e V ) ({E_{g1}} = 1.51{\ }eV, {E_{g2}} = 2.12{\rm{ eV}}) and ( E g 1 = 1.23   e V , E g 2 = 1.72 e V )   ({E_{g1}} = 1.23{\ }eV, {E_{g2}} = 1.72{\rm{ eV}}){\ } for the case of undoped Co3O4 and 9 % Mn-doped Co3O4, respectively. This shift means that the impurities would create energy levels. The structural analysis provides evidence that obtained powders were crystallized in cubic spinel structure. The complementary phase information is provided by FTIR spectroscopy. The FTIR study depicted the presence of four distinct bands characterizing Mn-doped Co3O4 cubic spinel-type structure. The Nyquist plots suggest that the equivalent circuit of Mn-doped Co3O4 films is an RpCp parallel circuit. It was found that the effective resistance Rp decreases, whereas the effective capacitance Cp increases with doping.