Tunable sensitivity of zirconium oxynitride thin-film temperature sensor modulated by film thickness

ZrO x N y thin films with different thicknesses were deposited on sapphire substrates using DC magnetron reactive sputtering. The electrodes were then deposited on the surface of the films using DC magnetron sputtering to produce temperature sensors. The electrical characteristics of the sensors from 4.3 to 300 K were determined by the physical property measurement system. The resistance–temperature ( R – T ) characteristic curves indicated that the reduction in the thickness of ZrO x N y films greatly improved the resistance and sensitivity of the sensors. In particular, the absolute value of temperature coefficient of resistance near room temperature reached 0.9% K −1 . The microstructure and optical properties of ZrO x N y films were evaluated using scanning electron microscopy, X-ray diffraction, Raman spectra, and spectrophotometric measurements. As the film thickness decreased, the microstructure changed from ZrN to poorly crystallized o-Zr 3 N 4 , and the bandgap was widened. Moreover, the conduction mechanism fitting results showed the crossover behaviors of Mott-variable range hopping (Mott-VRH) and thermal activation mechanisms upon changes in the thickness and temperature. The increased lattice distortion and phase transition in the ZrO x N y films and the extension of the Mott-VRH to the high-temperature region are responsible for the improved sensor sensitivity. This study provides a simple, low-cost, and highly sensitive solution for room-temperature sensors that can be widely used in temperature monitoring for industry, agriculture, and semiconductor manufacturing.