Mn–Co–Ni–O thin films prepared by sputtering with alloy target

The thin film of heat-sensitive materials has been widely concerned with the current trend of miniaturization and integration of sensors. In this work, Mn_1.56Co_0.96Ni_0.48O₄ (MCNO) thin films were prepared on SiO₂/Si substrates by sputtering with Mn–Co–Ni alloy target and then annealing in air at different temperatures (650–900 ℃). The X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) analysis indicated that the main crystalline phase of MCNO thin films was spinel crystal structure; the surface of the thin films was very dense and uniform. The electrical properties of the thin films were studied in the temperature range of –5–50 ℃. The MCNO thin film with a low room temperature resistance R₂₅ of 71.1 kΩ and a high thermosensitive constant B value of 3305 K was obtained at 750 ℃. X-ray photoelectron spectroscopy (XPS) analysis showed that the concentration of Mn³⁺ and Mn⁴⁺ cations in MCNO thin films is the highest when annealing temperature is 750 ℃. The complex impedance analysis revealed internal conduction mechanism of the MCNO thin film and the resistance of the thin film was dominated by grain boundary resistance.