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

Spinel AB2O4 oxide Mn1.4Co1.0Ni0.6O4 (MCN) films are fabricated on Al2O3 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.