With the additional preparations for the ESRF upgrade, which was entering a critical phase in 2007, the last year has been very busy for surface and interface science (SIS) at the ESRF. Two novel SIS beamlines are foreseen in stage one of the upgrade and a third one most likely in the second phase. This will result in a complete renewal of the existing portfolio of the ESRF SIS beamlines, presently comprising ID01, ID03, and ID32.

Major improvements were carried out at the three “core” SIS beamlines in 2007. The ID01 team commissioned a new high stability white beam monochromator, which is now suitable for sub-micrometre focusing. At ID03 the speed of the two diffractometers has been greatly increased with the help of the new ESRF “ICEPAP” stepper motor drives. Small-angle scattering, to study shape transitions in growth studies, is now routinely possible at ID03. Furthermore, a new UHV compatible high pressure chamber for GIXRD catalysis studies is presently being commissioned. At ID32 work has continued in preparation for the installation of a new ultra high vacuum system for photoelectron spectroscopy in 2008, which will allow the analysis of electron kinetic energies up to 15 keV with a resolution down to 20 meV. Furthermore, a new, fully equipped electrochemistry laboratory is now available for users close to the ID32 beamline.

Surface and interface science at the ESRF has always had a rather different bias to conventional laboratory-based UHV surface science. In the mainstream area, one exploits methods that specifically probe only the outermost few atomic layers of a solid. By contrast, X-rays allow one to probe beneath the surface, yet by suitable choice of experimental measurement conditions, X-ray scattering can also be surface specific. A major component of SIS at the ESRF has thus been to explore the properties of ultra-thin layers imposed by a surface or interface, such as in epitaxial growth of thin films, multilayers, quantum dots and, of course, buried interfaces per se. This remains a major strength of the facility. What is also true, however, is that mainstream surface science is shifting its centre of gravity as it aims to tackle problems of increasing complexity, and many of the resulting challenges can be addressed with great effect by X-ray scattering. For example, while UHV surface science studies are commonly undertaken with the aim of identifying basic mechanisms in heterogeneous catalysis, it is now recognised that in many such problems the mechanisms differ under UHV and ‘high’ pressure conditions, so the surface needs to be investigated under reaction conditions at pressures of the reactant and product gases up to 1 bar or more. Several specific examples of this type concern oxidation reactions (such as the CO oxidation reaction conducted in automobile catalytic converters) in which it appears that ultrathin oxide layers on the metal surface, only stable at elevated pressures, play a key role in the reaction. Optical methods such as X-ray scattering (and infrared spectroscopy) are almost the only methods available for in situ surface studies under these conditions, and such experiments, particularly in the special chamber at ID03, are exploiting the special capabilities of the ESRF to the full. One such example is described by Over et al., while Stierle et al. report the results of in situ studies of elevated pressure surface oxidation in a rather different system has been conducted on a special chamber at ID32.

A rather different case of surface complexity that retains the UHV environment is that of surface structures with a very large surface mesh. Tackling problems of this type was one of the earliest goals of surface X-ray diffraction at synchrotron radiation facilities, because the traditional method of low energy electron diffraction becomes intractable due to the computational complexity of multiple scattering calculations for such systems. While relatively few studies of this type are now conducted at the ESRF a recent investigation of the surface reconstruction of Sm(0001) at ID03, reported by Lundgren et al., is a particularly elegant example. The modified electronic environment of the reconstructed surface layer of Sm atoms leads to a shift of some 7 eV in the L-edge, allowing anomalous scattering to be used to provide chemical as well as structural information on this complex surface phase.

While also reflecting the trend to increasing complexity, a rather distinct and clearly identifiable trend in the surface science community is an increasing emphasis on nanoscience. Of course, investigations focussed on just the outermost few atomic layers of a solid have always been concerned with scientific phenomena arising from localisation (perpendicular to the surface) on the nanometre scale, as have investigations of ultrathin single and multiple layer structures. Pursuing the growing interest in the science resulting from nanometre localisation in two and three dimensions, however, is thus a natural development within this community, the traditional techniques of surface science providing many of the necessary tools, although with an increasing need for lateral resolution. Scanning probe microscopies have had a huge impact in this area and offer attractive real-space imaging, yet they are limited in their ability to be applied at high resolution to dynamic studies at elevated temperatures and pressures. In such cases, X-ray scattering provides crucial complementary information. One classic example of nanostructuring of a single crystal surface is adsorbate-induced faceting, in which an initially flat surface breaks into a ‘hill-and-valley’ morphology due to a change in the relative surface free energies of different surface orientations due to the adsorbed layer. In such phenomena the adsorbate may be a result of a simple gas-phase reaction, such as atomic oxygen from dissociation of the molecular species, but may also involve an ultra-thin film of metal atoms. The results of an investigation of this type of nanoscale faceting on W(111) induced by Pt deposition is reported by Revenant et al.

The more detailed short reports that follow include six contributions from the core ESRF SIS beamlines, and also two articles from the French CRG beamline BM32, which is almost entirely dedicated to SIS studies. Specifically, in addition the article by Revenant et al., there is a report on a novel technique using monochromatic and “white” X-radiation to obtain structure and strain of polycrystalline grains from Sicardy et al. Two studies are reported from experiments performed at ID01: Richard et al. have used a new way to study defects in crystals non-destructively, and Mocuta et al. describe experiments that employ a new technique, for which the ID01 staff have coined the name ‘X-ray diffraction microscopy’. The two contributions from ID03 deal with catalysis (Over et al.) and the determination of the Sm(0001) surface structure using anomalous diffraction (Lundgren et al.). The formation of an ultra-thin oxide film was studied in real time by Stierle et al. at ID32 and van Bokhoven et al. show how to identify the location of aluminium in the unit cell of zeolite crystals, which largely defines their functionality, with the help of the X-ray standing wave method.

D.P. Woodruff (University of Warwick) and J. Zegenhagen