In-situ coating technology for enhancing high temperature performance of ITO thin film resistance temperature detectors

Indium tin oxide (ITO) is a promising material for high temperature thin film resistance temperature detectors (TFRTDs) due to its high melting point and excellent conductivity. However, its performance under extreme conditions remains insufficiently explored. In this study, we fabricated ITO TFRTDs on Al₂O₃ substrates using magnetron sputtering and systematically evaluated their key performance metrics, including the temperature coefficient of resistance (TCR), repeatability, and thermal stability, from room temperature to 1000 °C. The results show that oxygen diffusion significantly affected the electrical properties of ITO films by altering the oxygen vacancy concentration, leading to a high repeatability error (ER, 23.3 %) and notable resistance drift (DR, 0.015 %/h). To address these challenges, a novel Al/Al₂O₃ coating was employed as an oxygen diffusion barrier. This robust coating effectively reduced the ER and DR by an order of magnitude, to 4.2 % and 0.0077 %/h, respectively. These findings underscore the significant potential of the in-situ coating technology to enhance the reliability and thermal endurance of thin film sensors in extreme environments.