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

Ruifeng Li,Wei Luo,Liang Yan,Xiaohua Zou,Qiuyun Fu,Zhiping Zheng

doi:10.1007/s40145-019-0348-y

Ruifeng Li, Wei Luo + Show 4 more

Open Access

https://doi.org/10.1007/s40145-019-0348-y

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Abstract

The thin film of heat-sensitive materials has been widely concerned with the current trend of miniaturization and integration of sensors. In this work, Mn1.56Co0.96Ni0.48O4 (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 °C). 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 °C. 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 °C. 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 °C. 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.

Highlights

Negative temperature coefficient (NTC) thermistors are widely used in temperature sensors, household appliances, infrared detection, and other fields due to their high sensitivity, good stability, and low price [1,2]
The main peak (311) of thin film is the strongest at 750 °C, which indicates that the MCNO thin film is highly crystalline and oriented at annealing temperature of 750 °C [12]
There is no pore at the grain boundary of the thin films, which facilitates the transmission of electrons and reduces the electrical resistivity of the material

Summary

Introduction

Negative temperature coefficient (NTC) thermistors are widely used in temperature sensors, household appliances, infrared detection, and other fields due to their high sensitivity, good stability, and low price [1,2]. The Mn–Co–Ni–O system materials with spinel structure (AB2O4) has become one of the most commonly used NTC thermistor materials because of its excellent negative temperature coefficient and good stability [3]. The main preparation methods of NTC thin films are radio frequency magnetron sputtering, evaporation coating, metal organic thermal decomposition, pulsed laser deposition, and so on [7,8,9,10,11]. The metal organic thermal decomposition method is characterized by good controllability and simple operation, but the composition and thickness of the thin film may be uneven. The thin films prepared by the magnetron sputtering have good crystallinity, high purity, good www.springer.com/journal/40145

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Conclusion