Probing Disordered Metallic Films With Surface Acoustic Waves

Amy Bylsma Engebretson and Brage Golding

Department of Physics and Astronomy, Michigan State University

A surface acoustic wave (SAW) can be generated and received by interdigital electrodes, or metal fingers, deposited onto a piezoelectric slab. A SAW is a sound wave which travels along the surface of a solid. Its wavelength is determined by the spacing of the fingers. The above SEM micrograph shows aluminum fingers on lithium niobate. The finger spacing of 1.36 micron (about 0.00005 inches) corresponds to the wave oscillating at frequencies near 700 MHz. By placing thin films of disordered metals in the path of the SAW, we can probe the interaction of the waves with the electrons and defects in the metal. At very low temperatures, near absolute zero, atoms that comprise the defects can absorb energy from the waves and move between two nearby positions. We are studying the characteristics of these transitions in order to arrive at a better understanding of the interactions between defects and electrons.