The effect of annealing process on the performance of strain nickel–chromium thin film sensor

Abstract

In order to reduce the resistance value of the sputtering thin film resistor grid and improve the adhesion of the film, a thin film sensor with the NiCr film as a sensitive layer on a 304 stainless steel substrate is annealed in the N2 environment. During the experiment, it is found that the different annealing temperatures (300 °C, 350 °C, 400 °C, 450 °C, and 500 °C) can effectively reduce the resistance value of the thin film resistor grid; the decrease is the largest at 450 °C, and the resistance value change is 1.77 kΩ. The small resistance value enables the thin film sensor to detect smaller strain and has higher measurement accuracy. The thin film has the strongest adhesion on the substrate at 350 °C and 30 min, which is about 37.5% higher than that of the sputtering state. The increase in adhesion makes the thin film less likely to crack and fall off prematurely, which can expand the measuring force range. In addition, the atomic force microscopy results demonstrate that the thin film annealed at a higher annealing temperature has higher surface roughness, which may be caused by the phenomenon of original grain clusters after annealing. In addition, the temperature coefficient of resistance value and strain sensitivity coefficient (kn) increase with the increase in the annealing temperature, with kn increasing only slightly.

Understanding the effects of annealing induced structural transformations on the UVC absorbance and other optical properties of RF sputter deposited Ga2O3 thin films

“…Clustering of particles is observed over the film surface with increase in thermal energy. As the annealing temperature increases, the energy of the particles increase and they become more likely to diffuse and aggregate [38]. The cracks observed on the surface of the film annealed at 900 • C are expected to be due to the strain experienced by the films at elevated temperatures due to the difference in thermal expansion coefficients of the Ga and quartz substrate [39].…”