Spectroscopic and electrial properties of manganese cobalt nickelate copper films prepared by chemical depopition

Thin thermistor films of Mn_1.56Co_(0.96-x)Ni_0.48 Cu_xO₄ with spinel structure were prepared on amorphous Al₂O₃ substrate by chemical solution deposition method at a temperature of 750°C in air, which is much lower than the traditional sintered temperature of 1100°C. The X-ray diffraction indicates that with the increase copper content, the preferred direction of crystalline is different under the same growth condition, but these films keep spinel structure well with increased crystallinity. The calculation of the grain size for all films have been performed by using the Scherrer's equation, and we found that the grain size increased with the increase of the content of Cu. Scanning electron microscope (SEM) analysis showed that their surfaces were smooth and dense, free from cracks. The values of characteristic temperature T₀, activation energy E and NTC(Negative Temperature Coefficient)α(295K) for Mn_1.56Co_(0.96-x)Ni_0.48 Cu_xO₄ films were obtained from their electrical properties. The result revealed that a lower Cu component corresponded to a higher value of α. Increasing Cu constituent, α decreased from-4.12% to-3.29%. The extinction coefficients of this films were determined by spectroscopic ellipsometry(SE) and their extinction coefficient peaks were identified.