Substrate effect on the temperature coefficient of resistance of La0.7Ca0.3MnO3 thin films prepared by metal organic deposition

Epitaxial La_0.7Ca_0.3MnO₃ (LCMO) thin films were successfully prepared by the metal-organic deposition process on various (001) single-crystal substrates: MgO, LaAlO₃ (LAO), SrTiO₃ (STO), and (LaAlO₃)_0.3-(SrAlTaO₆)_0.7 (LSAT). The crystallinity and the epitaxial growth of the LCMO films were characterized by X-ray diffraction (θ − 2θ scans and pole-figure analysis). The temperature dependence of the resistance of the LCMO/LSAT, LCMO/STO and LCMO/LAO films exhibit typical characteristics with a transition from the paramagnetic-insulator state to the ferromagnetic-metallic state at a temperature peak (T _p ) ranging from 258 to 270 K. However, the LCMO/MgO films exhibited a semiconducting behavior without any transition. Based on the R(T) measurement, we calculated the temperature coefficient of resistance (TCR) for a bolometric application and we obtained 22%/K, 10.2%/K and 27.5%/K for the film grown on the LSAT, STO and LAO substrates, respectively. This difference in the TCR properties is related to the strain induced by the lattice mismatch between LCMO and the different substrates.