Micro structural, electrical and optical properties of highly (2 2 0) oriented spinel Mn–Co–Ni–O film grown by radio frequency magnetron sputtering

Abstract Spinel AB 2 O 4 oxide Mn 1.4 Co 1.0 Ni 0.6 O 4 (MCN) films are fabricated on Al 2 O 3 amorphous substrate by radio frequency (RF) magnetron sputtering method at different sputtering powers. The surface morphology and microstructure of the films are studied by SEM, atomic force microscopy (AFM) and X-ray diffraction. A major advance is the sputtering deposition of highly oriented MCN thin films. Variable temperature electrical properties of the as-grown and post annealed samples are investigated in 230–325 K temperature range. The dependence of electrical properties on growth conditions is discussed in detail. The resistivity of annealed MCN films is about 240–250 Ω cm with a negative temperature coefficient of about  4% K −1 at room temperature, which is a breakthrough for thermal sensing application by RF sputtering method. Optical properties of the MCN samples are studied within 0.33-10 μm band, and the optical bandgaps for the as-grown and post annealed MCN samples are about 0.51 eV and 0.57 eV, respectively.