Lateral field excitation of well structures in quartz

Recently, there has been interest in the fabrication of multiple Quartz Crystal Microbalances (QCMs) on a single substrate, to create a sensor array. The QCM's are ldquowell structuresrdquo etched on an AT-cut quartz substrate, to isolate the devices from one another. However, such devices are ultimately subject to the limitations of the QCM configuration, requiring electrodes and wires on the sensing surface of the crystal substrate. The Lateral Field Excited (LFE) sensor is a novel sensing device that only requires electrodes on the backside of the substrate. With a bare sensing surface, the LFE sensor is a better choice for implementing a sensor array. The purpose of this paper is to present preliminary results on LFE well structures in quartz, which would be the fundamental building block of an LFE sensor array. Several well structures of varying depth and diameter were etched into AT-cut quartz crystals. The transverse shear mode was successfully excited in the LFE well structure, and data on the frequency response and center frequency vs. well depth and diameter are presented.