Book review: Noncontact atomic force microscopy (nanoscience and technology)

Edited by S. Morita, R. Wiesendanger and E. Meyer. Pp 435. Springer-Verlag. Berlin. 2002. Price £70.00 (Hardcover). ISBN: 3540431179

In many ways, the name “atomic force microscopy” is something of a misnomer, conjuring, as it does, images of single atoms contacting each other. Under the conditions typically used in commercial instruments designed for ambient operation, the contact area is much larger than a single atom and the kinds of loads employed (nN and greater) would generate pressures in excess of the tensile strength of any known material if applied through a single atomic contact. Thus it seemed, for many years, and the goal of measuring forces between single atoms remained apparently illusory. First hints that things were different came in the mid-1990s, with the emergence of modulation-based approaches to AFM that yielded apparently atomically resolved images of crystalline surfaces. Critically–and in contrast to the mirages that previously reflected “atomic resolution”–these images exhibited atomic defects. Many of the “atomic resolution” images obtained previously are thought to have arisen from interference effects as the rather large tip (draw a scale diagram of a 50 nm radius asperity alongside an atom!) slid across the periodic substrate. The new non-contact images were clearly different, however. From these beginnings the daughter technique of non-contact AFM (NC-AFM) was born, and ushered in new possibilities for the investigation of atomic structure and bonding at extremely high spatial resolution. This excellent book, compiled by a respected and experienced group of editors, provides both an introduction to the technique and an overview of its applications, with contributions from leaders in the field that provide an excellent snapshot of the state-of-the-art. It represents a fascinating insight into the remarkable new possibilities that NC-AFM offers. It remains the case that NC-AFM is a more challenging and specialised technique that the many other variants of AFM, with work being predominantly carried out in UHV on fairly well-defined surfaces. However, in return, it delivers astonishingly well-resolved data. NC-AFM provides images of surface crystal structure (such as the well-known 7 × 7 reconstruction of the Si(111) surface) with a spatial resolution comparable to that offered by STM. Images of semiconductor surfaces reveal atomic locations and facilitate the direct imaging of the locations of heteroatoms deposited, for example, by epitaxy. However, in contrast to STM, NC-AFM enables the imaging of insulators, too, including, for example, alkali halides and oxides. Images of atomic arrangements are not the only type of data provided. Recently, there have been advances in the investigation of chemical bonding interactions using NC-AFM, representing a significant further advance in sophistication: chemical force microscopy with the spatial resolution of STM. If an Si tip, with a terminal atom possessing a dangling bond, is approached towards a dangling bond on an Si surface, then the result will be the splitting of these atomic orbitals into bonding and antibonding orbitals, with an accompanying covalent bonding force that may be measured. These are, however, simply a few illustrations of the capability of NC-AFM. This comprehensive volume provides an accurate, informative and authoritative overview of the state-of-the-art. It covers all aspects of the methodology, from basic theory, through instrumentation to applications. There are chapters covering semiconductors, halides, oxides and organic molecular adsorbates. For a newcomer to the field, it would make an excellent starting point. For others interested in surface science, or other SPM techniques, it provides valuable insights into an important and comparatively recent tool that, it is hoped, will continue to expand its capability over coming years.

---