Advances in Acoustic Microscopy – serie

This is the second volume of Advances in Acoustic Microscopy. It continues the aim of presenting applications and developments of techniques that are related to high-resolution acoustic imaging. We are very grateful to the authors who have devoted considerable time to preparing these chapters, each of which describes a field of growing importance. Laboratories that have high-performance acoustic microscopes are frequently asked to examine samples for which the highest available resolution is not necessary, and the ability to penetrate opaque layers is more significant. Such applications can be thought of as bridging the gap be­ tween acoustic microscopy at low gigahertz frequencies, and on the one hand nondestructive testing of materials at low megahertz frequencies and on the other hand medical ultrasonic imaging at low megahertz frequencies. Commercial acoustic microscopes are becoming increasingly available and popular for such applications. We are therefore delighted to be able to begin the volume with chapters from each of those two fields. The first chapter, by Gabriele Pfannschmidt, describes uses of acoustic microscopy in the semiconductor industry. It provides a splendid balance to the opening chapter of Volume 1, which came from a national research center, being written from within a major European electronics industry itself. Dr Pfann­ schmidt describes the use of two quite different types of acoustic microscopes, and points out the advantages of each for specific purposes.

In 1992 Acoustic Microscopy was published by Oxford University Press, in the series of Monographs on the Physics and Chemistry of Materials. Reviews appeared in the Journal of Microscopy [169 (1), 91] and in Contemporary Physics [33 (4), 296]. At the time of going to press, it seemed that the field of acoustic microscopy had settled down from the wonderful developments in resolution that had been seen in the late seventies and the early eighties and from the no less exciting developments in quantitative elastic measurements that had followed. One reviewer wrote, "The time is ripe for such a book, now that the expansion of the subject has perceptively slowed after it was detonated by Lemons and Quate. " [A. Howie, Proc. RMS 27 (4), 280]. In many ways, this remains true. The basic design for both imaging and quantitative instruments is well-established; the upper frequency for routine imaging is the 2 GHz established by the Ernst Leitz scanning acoustic microscope (ELSAM) in 1984. For the most accurate V(z) measurements, the 225-MHz line-focus-beam lens, developed at Tohoku Univer­ sity a little before then, remains standard. The principles of the contrast theory have been confirmed by abundant experience; in particular the role of surface acoustic waves, such as Rayleigh waves, dominates the contrast in most high­ resolution studies of many materials.