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

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_{g1}} = 1.51{\ }eV, {E_{g2}} = 2.12{\rm{ eV}}) and ({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.

A Novel p-Type ZnCoxOy Thin Film Grown by Atomic Layer Deposition

“…As for the pure Co3O4 film, a poor transmittance of 30% can be detected, and the obtained spectrum presents two absorption signals in the visible region. The first one (300 nm ~ 400 nm) is associated to the O 2-and Co 2+ charge transfer process, and the other (500 nm~ 600 nm) is from the O 2-and Co 3+ charge transfer, with this being in agreement with the literature [23]. Meanwhile, the ZCO (1:1) films exhibit a remarkable transmittance close to that of pure ZnO, which confirms that the ZCO film with a 1:1 deposition ratio is dominated by ZnO composite while the growth of Co3O4 is inhibited, with this phenomenon being consistent with the XRD results.…”

Experimental Study of Precursor Concentration the Co3O4 Thin Films Used as Solar Absorbers

“…Note that the crystallite size values decrease with the increase of the solution molarity. We can interpret the decrease in crystallites size (degradation of crystal quality) by the increase in nucleation centers with the increase in precursor concentration; these results are comparable with those of other authors [19].…”

Electrochemical Performance of Iron-Doped Cobalt Oxide Hierarchical Nanostructure

“…For comparison, the band-gap of Mn-doped Co 3 O 4 is reported to be 1.51 eV [61], Sm-doped Co 3 O 4 is reported to be 3.57 eV [62], and Cr-doped Co 3 O 4 to be 2.44 eV [63]. The occurrence of a voltage plateau in GCD curves confirms the pseudocapacitance behavior of electrodes concerning their discharging period [31].…”

“…The superior performance of the FexCo3-xO4 electrode results from the significant decrease in the band-gap upon Fe doping, as elucidated in the DFT study below. For comparison, the band-gap of Mn-doped Co3O4 is reported to be 1.51 eV [61], Sm-doped Co3O4 is reported to be 3.57 eV [62], and Cr-doped Co3O4 to be 2.44 eV [63]. The cyclic stability of Fe x Co 3-x O 4 electrodes was evaluated by repeated chargedischarge measurements up to 5000 cycles at a constant current density of 10 A/g in the potential range between 0.0 to 0.6 V in 3M KOH, as shown in Figure 8.…”