Cr-N Strain Sensitive Thin Films and Their Pressure Sensor Applications

The preparation of nitrogen added chromium thin films and their electrical properties were investigated. We found out that the N added Cr thin films indicated negative temperature coefficient of resistivity (TCR). Furthermore, the TCR changed from negative to positive values by annealing and became zero in a middle step of the change. The observed behavior was considered to be related to the structural transformation between δ-Cr and α-Cr by the addition of nitrogen or the annealing. The strain gauge factors (Gf) of the specimens with nearly zero TCR showed huge values of about 9 in maximum, which was verified to exceed those of conventional strain gauge metallic materials by a factor of about 4.5. These Cr-N thin films should be noteworthy as the new type high sensitive strain gauge materials. In this paper, the fundamental experimental results will be described, as well as some demonstrations on the high sensitive pressure detection using the Cr-N films formed on a metal diaphragm.