Galfenol thin films for surface acoustic wave generation

Abstract

This thesis investigates the use of magnetostrictive Galfenol thin films for the production of surface acoustic waves along a piezoelectric, lithium niobate, surface via the magnetostrictive effect. Using the combination of magnetostriction for surface wave actuation and piezoelectric detection it is postulated that a device of this type will produce a frequency doubling when driven with a magnetic field. This thesis investigates this type of device through multiphysics simulation using the software, COMSOL, showing how the design dimensions effect the operating frequency, and demonstrating the frequency doubling effect. Included in the modelling is the effect of magnetostrictive film thick on magnitude of the signal produced. The thesis outlines the fabrication steps to produce a device for investigation, with the radio frequency (RF) sputtering method chosen to produce the Galfenol film, and energy dispersive X-ray (EDX) analysis to determine the film composition. Electron-beam (E-Beam) evaporation is used to pattern the lithium niobate substrate with a set of gold thin film interdigital transducers (IDTs) for the piezoelectric detection of the surface wave. An experimental setup is describe that uses a pulsed magnetic field is used to actuate the magnetostrictive films, with the IDTs connected to an oscilloscope to measure the electric output and confirm s surface wave. However, the device operation is not experimental verified within this work, possibly own to weak production of surface waves due to the thickness of the film in combination with a poor signal transfer by IDTs for measurement.