Piezoresistive Graphene SAW Transducer

Abstract

Mechanical motion provided by Surface Acoustic Wave (SAW) devices is a popular means for high-sensitivity sensing and detection of any perturbation in the path of the SAW. The unique energy confinement to the surface, ease of fabrication, and packaging makes SAW devices easy to implement. One of the key challenges which limits the sensitivity of SAW devices is the IDT capacitance at high frequency, which requires impedance matching, and capturing the signal at the RF frequency. In this paper we investigate a graphene piezoresistive pickup for sensitive SAW amplitude measurement instead of using traditional IDTs, which generates a DC current signal corresponding to the RF power in the SAW wave. We demonstrate enhanced gauge factor (GF) of graphene piezoresistive transducer in a SAW resonator operating at 200MHz, with a $\mathbf{Q}\sim 6000$ . RF signal (3 V) applied to the input IDT results in 954 pm surface displacement at the antinodes of the SAW. By tuning the applied external voltage, we demonstrated effective gauge factor (EGF) of the graphene piezoresistor $\sim 1 \mathbf{x} 10^{8}$ , a result of a digital measurement approach to change in resistance around the DC operating point of the graphene transducer.