Effect of composition and microstructure on temperature coefficient of resistance of polycrystalline $La1−xCaxMnO3$ thin films

Polycrystalline $La1−xCaxMnO3$ films were rf-sputtered on Si substrates coated with $SiO2,$ and the effects of deposition parameters on the temperature coefficient of resistance (TCR) values were investigated. For the temperature higher than the metal–insulator transition temperature $(Tp),$ the temperature dependence of resistance can be described by using the small polaron model, and the TCR value increases with the activation energy $Ea$ for the polaron hopping. For the temperature higher than $Tp,$ increasing the oxygen or Ca content of the film results in the decrease in resistivity, $Ea,$ and TCR value. The resistivity and TCR value are also reduced in large-grained films. Applying a substrate bias can enhance the TCR value.