Fabrication and assessment of Mn–Co–Ni–Nb–O composite films: structural, optical, and electrical properties

Mn_1.56−xCo_0.96Ni_0.48Nb_xO₄ (MCNN) composite films with different Mn/Nb ratios were synthesized on a SiO₂/Si substrate via the chemical solution deposition method. The film structure and morphology were investigated via X-ray diffractor (XRD), Raman spectroscopy, scanning electron microscopy, and atomic force microscopy. The optical properties of the composite films were explored via ellipsometry. The XRD results indicated that MCNN was a composite of the Mn-based spinel oxide and the nickel/cobalt niobates. The morphology of the MCNN films improved with increasing Nb content from 0.2 to 0.4. The partial replacement of Mn into Nb significantly improved the optical properties of the composite films over the incident photon energy range of 1.0–5.0 eV. The optical absorption mechanism of the composite films has also been discussed.