Microstrain-range giant piezoresistivity of silicon oxycarbide thin films under mechanical cyclic loads

Abstract

In the present study, thin-film strain gauge element arrays were prepared based on large-area silicon oxycarbide thin films and lithographic deposition of structured electrodes. The individual strain gauge elements were systematically investigated concerning their piezoresistive behavior at ambient temperature and shown to possess giant piezoresistivity with gauge factors in the range of 3–5 × 103. This has been correlated with the large charge carrier mobility in the silicon oxycarbide thin films (i.e., 186 cm2 V−1 s−1) as well as with a unique phase composition and morphology thereof, consisting of high-conductivity carbon-rich segregations homogeneously dispersed within a silicon oxycarbide-based matrix. The studied strain gauge elements were evaluated in both cyclic tensile and compression load modes and showed excellent reversibility and short response times. The process capability of the strain gauge elements has been statistically assessed and revealed good robustness and replicability which may be further improved. The present work provides a robust and highly reproducible manufacturing process for an ultrasensitive strain gauge prototype and thus points towards a great potential concerning the use of silicon oxycarbides in MEMS-related applications.