Optical and electrical properties of Mn_1.56Co _0.96Ni_0.48O₄ thin films

Mn_1.56Co_0.96Ni_0.48O₄ (MCN) films with different layers have been prepared on Al₂O₃ substrate by chemical solution deposition method. The microstructures, optical and electrical properties of the films are investigated. X-ray diffraction and microstructure analyses show good crystallization and both the crystalline quality and the grain size are improved with the increasing thickness of the films. Mid-infrared optical properties of MCN films have been investigated using transmission spectra. The results show the red shift of absorption with the increasing film thickness and the energy gap E_g decrease from 0.6422 eV to 0.6354 eV. All the MCN films show an exponential decrease in the resistivity with increasing temperature within the measured range. The temperature dependence resistivity can be described by the small polarons hopping model. Using this model, the characteristic temperature T₀ and activation energy E of the MCN films were derived. With the film thickness increase, the T₀ and E of the MCN films increase. The calculated room temperature coefficient of resistance (TCR) of MCN film with 100 layers is -3.5% K^-1. The MCN films showed appropriate resistance and high value of TCR, these advantages make them very preponderant for thermal sensors.