Abstract
We investigate surface acoustic wave (SAW) propagating in a graphene with tuned Fermi-level EF and the modulation of acoustic current by two SAWs generated by a cross interdigitated transducers (IDT). Our device consists of CVD-grown graphene coated with an ion-gel gate on top, and transferred on LiNbO3 substrate. Two IDTs are employed outside graphene area and are placed at a right angle to each other. Interference patterns of SAW are formed at the graphene area by applying a high frequency ac voltage to the IDTs, and EF of graphene is tuned biasing dc voltages on the ion-gel gate. We find the phase shift and SAW attenuations evolved with EF by measuring acoustic currents in graphene. Moreover, as two SAW are launched simultaneously we are able to modulate the acoustoelectronic currents, suggesting the formation of a two-dimensional ‘‘egg-carton’’ density fluctuation in graphene. Our results have a strong implications in the development of novel acoustoelectronic devices, and pave a way to study modulated 2D massless Dirac electrons.