Scanning Acoustic Microscopy

Abstract

Scanning acoustic microscopy is a form of microscopy based on the generation and detection of elastic waves in solids. The basic mechanism is the interaction of an acoustic wave with a specimen and the consequent generation of acoustic waves inside the material. Such interaction is characteristically different from optical or electronic interactions, and is mainly dependent on the mechanical properties of the specimen. As a consequence, acoustic microscopy provides an important and complementary source of information for the examination of materials. Two major advantages are obtained using an acoustic microscope. First, acoustic waves are capable of penetrating materials that are opaque to other kinds of radiation. As a result, the acoustic microscope can image subsurface characteristics of materials without the necessity of etching or coating the surface of the sample. The second advantage relies on the origin of contrast in acoustic microscopy lying in the interaction of elastic waves with local variations in mechanical properties. Using an acoustic microscope it is therefore possible to study, with high resolution and sensitivity, mechanical properties of the specimen such as density, elasticity, and viscosity. In the field of material science, applications of acoustic microscopy are quite wide and range from the analysis of cracks and other defects in engineering materials to the study of integrated circuits and electronic components. Moreover, recent advances in quantitative acoustic microscopy enable the determination of mechanical material parameters on a microscopic scale.