Effect of thickness on the electrical properties of PdCr strain sensitive thin film

Abstract

The electrical properties of palladium chromium strain sensitive films with various thicknesses were fabricated onto sapphire substrates by direct current magnetron sputtering are investigated. The results show that the electrical properties of PdCr strain films are strongly dependent on their thickness. The square resistance and the temperature coefficient of resistance of PdCr strain sensitive films are dramatically decreased when the thickness of PdCr films that thinner than 232 nm, then the downward trend of electrical properties tends to be stabilized until 933 nm. The PdCr films with 933 nm thickness show a relative minimum temperature coefficient of resistance and excellent repeatability from room temperature to 800 °C. Furthermore, the stability of PdCr thin film strain gauges are measured at 600 and 800 °C by drift test, which reveals that the average resistance drift rate of PdCr strain film with 48 nm is almost ten times larger than that of the films with thickness of 933 nm. The above results further verify that the PdCr film with thickness of 933 nm possesses relatively superior electrical properties. Moreover, the strain response of PdCr thin film strain gauge with 933 nm on DZ22 Ni-based superalloys is studied, which indicates that the values of resistance are synchronous response to the strain implying the PdCr thin film strain gauge has a fast response to strain, and the gauge factor is 1.80, 1.88, 1.90 and 1.93 at 25, 400, 600 and 800 °C, respectively.