Exploiting nonlinearity for sensitivity enhancement of novel tunable and low-power thin-film Piezoelectric-on-Silicon (TPoS) micromachined gas sensor

This paper presents an innovative tunable and low-power micromachined thin-film piezoelectric-on-silicon (TPoS) antisymmetric weakly-coupled gas sensor, showing high sensitivity by exploiting its nonlinearity. Adopting a special Aluminium Nitride (AlN) piezoelectric layer doped with Silicon (Si) in TPoS devices significantly improved the system's power consumption during resonance frequency tuning by 41.2 %. Two sensing theories based on linear and nonlinear behaviour are explored as operating the system near its buckling bifurcation (i.e., before and after) for increasing Helium concentrations. The results yield high linear frequency shifts of 3.60 ppm/Hz and 9.96 ppm/Hz at two operation points. Nonlinear fold bifurcation jump was exploited to enhance the sensor sensitivity, proving that such a triggered mechanism can be used as an alarming gas sensor with adjustable thresholds of 2000 ppm (i.e. 0.2 %) of Helium. The novel TPoS gas sensor shows great potential in low-power consumption, high sensitivity, and multi-functionality for environmental monitoring and hazard gas-controlling measure applications.