An Ultrahigh-Precision Thin-Film Platinum Resistance Sensor for Ocean Temperature Measurements

Abstract

This study presents the design and fabrication of an ultrahigh-precision platinum thin-film temperature sensor without an adhesion layer, which effectively eliminates the performance degradation caused by adhesion layer diffusion during high-temperature annealing. A 1- $\mu $ m-thick platinum film was deposited on an alumina substrate via segmented magnetron sputtering, followed by annealing in air at temperatures ranging from $500~^{\circ }$ C to $900~^{\circ }$ C. The resistance-temperature relationships of the sensor were characterized over the $0~^{\circ }$ C– $35~^{\circ }$ C range under various annealing conditions, with a particular focus on the temperature coefficient of resistance (TCR). The morphological and grain size analyses of the platinum film were conducted using X-ray diffraction (XRD) and scanning electron microscopy. Results indicate that optim al sensor performance was achieved with an annealing temperature of $800~^{\circ }$ C for 2 h, which leads to an increase in the TCR from $2.36 \times 10^{-{3}}$ /°C to $3.65 \times 10^{-{3}}$ /°C. Precision calibration and stability tests show that the sensor achieved an excellent measurement accuracy of $0.0019~^{\circ }$ C and a maximum temperature drift of only $0.0009~^{\circ }$ C per month over a six-month period. These results indicate that the platinum thin-film sensor exhibits outstanding performance, making it particularly suitable for high-precision ocean temperature measurement applications.