Characterization of TaxO5−y thin films grown by HiPIMS reactive sputtering for temperature sensing applications

Temperature sensors with a negative temperature coefficient are widely used in various sectors because of their numerous benefits and practical applications. However, linearity over narrow ranges restricts extensive use compared to other temperature sensors, especially in the cryogenic region. This study investigated tantalum oxide (TaxO5−y) thin films and their potential for temperature sensing capabilities spanning the cryogenics to the room-temperature region due to their strong chemical, physical, and electrical properties, such as a wide bandgap, chemical stability, high refractive index, and dielectric constant. The properties of thin films partially depend on fabrication techniques/parameters. This research uses the high-power impulse reactive sputter technique to produce TaxO5−y thin films. The thin film of 200 nm TaxO5−y depends on temperature, and the resistance vs temperature (R-T) shows almost linear relationships in the 20-320 K range. The absolute value of the temperature coefficient of resistance of this sensor at 294 K increased to −1.1% K−1 as it grew. The annealing effect on R-T properties, including physical and crystalline characteristics, was investigated for optimization, and bandgap energy was found to be 4.16 ± 0.025 eV. Annealing at different temperatures causes a decrease in resistance and a slight change in the R-T curve due to its crystallization.