Surface acoustic waves (SAWs) are elastic waves that propagate on the surface of a solid, much like waves on the ocean, with SAW devices used widely in communication and sensing. The ability to dynamically control the properties of SAWs would allow the creation of devices with improved performance or new functionality. However, so far it has proved extremely difficult to develop a practical way of achieving this control. In this paper we demonstrate voltage control of SAWs in a hybrid graphene-lithium niobate device. The velocity shift of the SAWs was measured as the conductivity of the graphene was modulated using an ion-gel gate, with a 0.1% velocity shift achieved for a bias of approximately 1 V. This velocity shift is comparable to that previously achieved in much more complicated hybrid semiconductor devices, and optimization of this approach could therefore lead to a practical, cost-effective voltage-controlled velocity shifter. In addition, the piezoelectric fields associated with the SAW can also be used to trap and transport the charge carriers within the graphene. Uniquely to graphene, we show that the acoustoelectric current in the same device can be reversed, and switched off, using the gate voltage.
The procedure describes the derivation of boundary integral equations for surface acoustic waves propagating under periodic metal strip gratings with piezoelectric films. It takes into account the electrical and mechanical perturbations, including the effects of mass loading caused by the gratings with an arbitrary shape. First, an integral equation is derived with line integrals on the boundaries within one period. This derivation is based on Hamilton's principle and uses Lagrange's method of multipliers to alleviate the continuous conditions of the displacement and the electric potential on the boundaries. Second, boundary integral equations corresponding to each substrate, piezoelectric film, metal strip, and free space region are obtained from the integral equation using the Rayleigh-Ritz method for admissible functions. With this procedure, it is not necessary to make any assumptions for separation of the boundary conditions between two neighboring regions. Consequently, we clarify the theoretical basis for the analytical procedure using boundary integral equations for longitudinal LSAW modes. 相似文献
Recently, in the electronics and pharmaceutical industries, miniature devices that can transport a tiny amount of dry powder with a particle size of 100 μm or less are desired. We therefore focused on a surface acoustic wave (SAW) device, and we experimentally studied an interdigital transducer (IDT) that generates the SAW. As a result, it was found that an IDT with a 2-mm pitch size at a 90° inclination angle, against the perpendicular direction of a piezoelectric wafer (127.8° y-rotated x-propagating LiNbO3) orientation flat, had a high efficiency of copper powder (about 100-μm particle size) transport. Then, to investigate the availability of a SAW actuator with this highly efficient IDT, we fabricated a miniature feeder (13-mm height × 18-mm width × 78-mm length) mounted with a hopper on the SAW actuator and carried out a powder supply experiment. As a result, it was found that, when 1 W of electric power was applied to the IDT of the feeder, the powder supply capability of the feeder was about 18 mg/s. From this fact, it was experimentally shown that a SAW actuator with a highly efficient IDT has a great potential to control dry powder with superior accuracy. 相似文献
