SPATIALLY RESOLVED SURFACE ACOUSTIC WAVE STUDIES FOR IMAGE PROCESSING AND CHEMICAL SENSORS

摘要

The interaction between a surface acoustic wave (SAW) and photo-generated charge carriers in a piezoelectric semiconductor substrate leads to pronounced changes in the transmission properties of the SAW. Depending on the charge carrier density one observes a wave attenuation and a change in sound velocity in the SAW delay line. Using specially designed surface acoustic wave transducers, we are able to spatially resolve this interaction. The transducers used for this purpose consist of fan shaped inter-digated metal fingers, which show a broadband frequency transmission. It turns out, that for such transducers the excited SAW propagates on a narrow path, whose position can be controlled by the driving frequency. If the SAW propagates along a path where defined molecules from the environment are adsorbed, the SAW transmission properties are also changed. This can be used for the chemical sensors.