Thin film material properties analysis with quartz crystal resonators

Abstract

Quartz crystal resonator sensors can be employed for the determination of properties of thin films prepared on their surfaces. If the sensor provides both the frequency shift and the motional resistance in its response, more information can be extracted than using the traditional quartz crystal microbalance. The acoustic load concept allows the direct calculation of material parameter values directly from measured responses and (assumed) film properties. The computations can be easier and faster compared with experiments using the complete impedance analysis. The accuracy of the model is sufficient for most applications. Some film properties are not covered by the one-dimensional transmission line model. Under certain circumstances a generalization of the one-dimensional film parameters can be applied to describe those effects. Although the parameters lose part of their original meaning, it can be a helpful way to predict the effect on the (generalized) acoustic load and hence the sensor response.