Acoustic wave field imaging and measurement by scanning probe methods

Abstract

Acoustic waves are widely utilized for the investigation of elastic properties of solids and layered systems. However, since the spatial resolution is limited due to Abbe’s criteria, small structures can not be investigated by elastic waves using conventional techniques. These limitations can be overcome by applying scanning probe methods. A scanning acoustic force microscope (SAFM) and a scanning acoustic tunneling microscope (SATM) for the measurement of high-frequency surface acoustic waves were developed. The methods are based on the mixing at the nonlinearities of the tip-to-sample interactions. The amplitude and phase of the surface oscillation can be imaged with a lateral resolution in the nanometer range. The phase velocities of surface acoustic wave for propagation distances as small as 20 nm were measured. By using the SATM the surface oscillation was measured on the atomic scale. The SAFM was applied for the investigation of high-frequency interdigital transducers up to some GHz. Scattering and dispersion of elastic waves were studied. Recently, it has been shown that in-plane polarized surface acoustic waves can be detected by using a scanning acoustic probe technique. The phase velocity of Love waves in quartz-layered systems was determined.