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.