Low Loss Performance of Two-Port SAW Resonator Sensor with Electrophoretically Deposited Graphene Oxide on Reflectors

We report the fabrication and characteristics of a two-port SAW resonator coated with graphene oxide (GO) as a sensing film only on to the electrodes of the reflectors. The GO was coated directly on the reflector electrodes of the SAW device via electrophoretic deposition (EPD). The deposited GO coating was characterized using field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The comparison of a reflector-coated SAW sensor and IDT-coated SAW sensor revealed that the reflector-coated SAW sensor exhibited damping but had minimal losses, while the IDT-coated SAW sensor was not able to provide reliable measurements. Furthermore, the reflector-coated SAW sensor demonstrated minimal additional losses after coating compared to reported conventional SAW-based sensors that had a sensing film on the IDTs or the whole surface. Moreover, the reflector-coated SAW sensor showed good linearity, repeatability, and stability during relative humidity sensing experiments, demonstrating the potential of the proposed reflector coated two-port SAW resonator for sensing applications.