Surface acoustic wave device designed to monitor frequency shifts due to adsorption of mass onto a piezoelectric crystal

Surface acoustic wave (SAW) devices have recently been utilized as extremely sensitive chemical sensors. This study was conducted to investigate the feasibility of an experimental apparatus designed to monitor, both statically and dynamically, the frequency shift in a SAW device while adsorption occurred. The apparatus was designed so that any frequency shift detected would be due solely to adsorption, not temperature or pressure differences. A Cahn microbalance was installed with the SAW apparatus to allow quantitization of the mass adsorbed onto the surface of the SAW. It was anticipated that changes in surface concentrations of less than one percent of a monolayer could be detected with this apparatus. Adsorption studies leading to frequency shift versus pressure curves were to be conducted from a total pressure of 1.0 X 10^-7 torr up to atmospheric conditions and from ambient temperatures up to 45°C. The following chapters discuss problems associated with acquiring this information and make recommendations for modifying the apparatus so that the original experimental objective may be attained.