FREQUENCY AND ATTENUATION RESPONSE OF ACOUSTIC PLATE MODE DEVICES COATED WITH POROUS OXIDE-FILMS

The response behavior of coated acoustic plate mode (APM) devices upon exposure to ionic solutions was evaluated. The response sensitivity ( frequency shifts and attenuation) of APM devices coated with porous ox ide films increased by factors of ca. 4-30 compared with an uncoated d evice upon exposure to ionic solutions. These responses arise predomin antly due to acoustoelectric coupling and are consistent with enhanced pore conductivity. A previously derived model for the acoustoelectric response of uncoated APMs is inadequate for predicting the magnitude of coated APM responses and needs to be modified to account for the pr operties of porous films. Frequency responses are consistent with enha nced conductivity of the solution within the porous coatings. Film por osity, pore size distribution, and film thickness are identified as pa rameters influencing response sensitivity.