High‐Strain Characterization of Polycrystalline Sputtered Vanadium Dioxide Resistors on Polyimide Membranes

This paper demonstrates the continuous and exponential increase of the gauge factor of strained polycrystalline vanadium dioxide (p‐) resistors. The devices are integrated on a 2.5 ‐thick polyimide membrane using a monolithic processing scheme. The membrane is assembled on a bulge‐test setup, and pressure cycles up to 100 kPa are applied. The deflection profile of the pressurized membrane is measured to calibrate an FEM Comsol model. The model is used to recover the strain field in the p‐ devices. A biaxial tensile strain of 0.3% is reached. IV measurements are performed at each pressure step. An exponential increase in resistance is observed with a variation of 145% at 0.3% strain. Cycling of the pressure shows that permanent defects are induced in the p‐ for strain above 0.1%. The resistance variation follows a hysteresis while subjected to increasing and decreasing strain. When strained to 0.3%, a 10% permanent resistance decrease is observed. The gauge factor is extracted from the IV measurements and showcases a continuous and exponential variation up to 4180 at 0.2% of strain. This showcases the limits of p‐ for strain sensing passed 0.1% deformation, highlighting the importance of grain boundary dislocations occurring in the material.