Progress in nanoscience and nanotechnology requires tools that enable the imaging and manipulation of mater at the atomic and molecular scale. During the last two decades or so, scanning probe based techniques have proven to be most versatile in this regard. Among the various probe-based approaches, atomic force microscopy (AFM) stands out in many ways, including the total number of citations and the breadth of possible applications that range from materials characterization to nanofabrication and biological studies. However, while nanometer scale operation in different environments became routine, atomic resolution imaging remained elusive for a long time.

The reason for this initial deficiency was that contact with the sample blunts atomically sharp tips, which are mandatory for successful atomic resolution imaging. This problem has been overcome in the mid-1990s with the introduction of noncontact atomic force microscopy (NC-AFM), which represents a version of AFM where the cantilever is oscillated close to the sample surface without actually ‘touching’ it. This allows preserving the atomic sharpness of the tip while interaction-induced changes in the cantilever’s resonance frequency are used to quantify the tip-sample distance. Since then, progress has been steady and includes the development of commercial instruments as well as the addition of many new capabilities beyond imaging such as the identification and manipulation of individual atoms.

A series of annual international conferences, started in Osaka in 1998, have contributed significantly to this outstanding performance. Since then, its annual conferences have established as the leading meetings for NC-AFM related topics. Here we report on the outcome of the most recent conference from this series, held at Yale University in New Haven, Connecticut, from August 10 to August 14, 2009. The conference program, which can be downloaded at http://www.eng.yale.edu/ncafm2009, reflects the maturity of this field, with an increasing number of groups developing strong activities that involve novel approaches and applications covering areas well beyond the original vacuum-based imaging. The conference was complemented by a vendor exhibition featuring the latest developments in NC-AFM equipment and accessories, and a workshop on the measurement of Casimir forces, which included specialized sessions on August 10 with two joint sessions on August 11. For the first time, close interaction between the NC-AFM and the Casimir force communities was established, producing valuable synergies regarding the measurement of small forces at short range. 133 participants from 15 different countries attended the NC-AFM conference and the Casimir workshop. Thereby, the strong contingent from the US (38 participants) reflects the success of the conference in promoting NC-AFM in the US, where relatively few groups are currently employing this technique.

One of the most remarkable developments highlighted at the conference is the extension of dynamic imaging modes to high-resolution operation in liquids, which seemed almost unthinkable just a couple of years ago. State-of-the-art measurements do not just result in atomic resolution, but enable three-dimensional mapping of hydration layers on surfaces with molecular resolution. These developments are already having significant impact in the highly competitive field of biological imaging under physiological conditions. Other areas particularly noteworthy are (1) the continuing development of sophisticated force spectroscopy procedures that are able to map the complete 3D tip-sample force field on different surfaces, which are now able to resolve of the internal structures of molecules and to achieve the mapping of local lateral forces with picometer resolution; (2) the considerable resolution improvement of Kelvin probe force microscopy (reaching, in some cases, the atomic scale), which is accompanied by a thorough, quantitative understanding of the contrast observed; (3) the perfecting of atomic resolution imaging on insulating substrates (in particular oxides), which helps reshaping our microscopic understanding of surface properties and chemical activity of these surfaces; and last but not least (4) the instrumental and methodological developments that pave the way to the atomic-scale characterization of magnetic and electronic properties of nanostructures.

Next year’s conference, which is held August 2-5, 2010, in Kanazawa, Japan, will be accompanied by satellite workshops on bio-imaging, solid-liquid interface, and SPM standardization (satellite workshops are scheduled on July 31-August 1). More information can be found at http://www.afm.eei.eng.osaka-u.ac.jp/ncafm2010/.