Thin-film materials for SAW devices

The status of thin films for SAW (surface acoustic wave) devices is reviewed through the framework of a process-structure-property network commonly considered in the thin-film area. Different branches of this network are considered and practical examples from SAW thin films illustrate the nature of these relationships. Such considerations lead to a better understanding of thin-film nucleation and growth processes and the deposition parameters that result in the best microstructures for SAW devices. The discussion is limited to the physical vacuum-deposition processes of thermal evaporation and sputtering, which traditionally have been the most commonly used SAW thin-film processes. Such depositions can be made at relatively low substrate temperatures. The present directions of thin-film research and how they may affect future SAW device developments are considered