SAW-thin-film acoustoelectric in-situ observation and measurement

The thin-film acoustoelectric effect in surface acoustic wave (SAW) devices describes the interaction of electrical energy between a SAW in a piezoelectric medium and a thin-film placed in the wave´s propagation path. The real-time observation of the thin-film acoustoelectric interaction is useful in the design and characterization of SAW-based thin-film chemical and physical sensors (i.e. temperature, humidity, viscosity, voltage, current, hall effects, etc.). An in-situ test fixture was designed to be mechanically, thermally and electrically stable. Data has been taken for many SAW devices and over a wide range of frequencies. The results show that the use of the in-situ procedure yielded: good agreement between theoretical predictions and the measured data, characterization a SAW-H₂ gas sensor in real-time and various methods to calibrate the film deposition system and procedure. This paper presents the approach taken in configuring an electron beam evaporation system for ultra-thin-film characterization and the design of test fixtures, data acquisition configuration, and experimental procedures to extract and analyze SAW parameters in real time, and to extract the thin-film properties under test.