Layered Surface Acoustic Wave Devices for Film Characterization and Sensor Applications
Open Access
- Author:
- Pedrick, Michael Kevin
- Graduate Program:
- Engineering Science and Mechanics
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- January 10, 2007
- Committee Members:
- Bernhard R Tittmann, Committee Chair/Co-Chair
Joseph Rose, Committee Member
Mark William Horn, Committee Member
Samia A Suliman, Committee Member
James Patrick Runt, Committee Member - Keywords:
- Radiation Detection
Finite Element Model
Love Waves
Surface Acoustic Wave - Abstract:
- This work has introduced novel applications for Layered Surface Acoustic Wave (SAW) devices along with concepts for enhanced sensitivity via refined modeling techniques. The derivation of Love Wave and Rayleigh wave propagation pertinent to SAW substrates with thin film overlayers was explored. Novel aspects were presented for Finite Element analysis of Layered SAW sensors. This included coordinate transformations of model geometries to coincide with crystallographic orientations known to generate Surface Skimming Bulk Waves (SSBW) and various Rayleigh wave types of propagation in ST Quartz, 900 rotated ST Quartz, and 770 Y rotated Lithium Tantalate. This work has shown for the first time, FEM prediction of SSBW, Generalized SAW and High Velocity SAW waves. Rayleigh damping properties were extended to develop a Finite element model capable of predicting Layered SAW response to glass transition in a polymer film. The ability to monitor localized mechanical behavior in a PMMA film was explored with Love Waves generated by 900 rotated ST Quartz and Shear Vertical (SV)-SAWs generated by 770 Y rotated Lithium Tantalate. Similar trends were found experimentally as compared to the Finite element models. The capability of Love Wave devices for monitoring polymer film curing behavior was investigated. The ability to qualitatively asses the bond quality between film and substrate was also demonstrated based on the characteristics of the transmitted frequency response. The results of these developments have laid the ground work for developing diagnostic tools to better characterize film behavior in practical applications Several sensor applications for Layered SAW devices were discussed. The Shear Horizontal displacement of the Love Wave device was exploited to demonstrate the capability of such a sensor for ice detection. A clear distinction between air, water, and ice loading was found with Love Waves whereas SV-SAWs were unable to distinguish between liquid and ice loading. The concept of a Layered SAW radiation sensor based on ion modification of a polymer film was presented for the first time. A Finite element model based on published experimental modification data was presented and validated experimentally with the UV cross-linking of an SU-8 photoresist film. Frequency changes on the order of parts in 104 were demonstrated for apparent Elastic Modulus changes of 1-2 GPa.