Introduction

With the ESRF Upgrade Programme launched in November, the starting signal was given for developing concrete plans for the future upgrade and refurbishment of the surface and interface science (SIS) beamlines. Conceptual design reports are required for the meeting of the Science and Advisory Committee in spring 2009. ID01 may be transformed into a 130 m long beamline for nanofocusing and coherent diffraction imaging (CDI) and ID03 may be relocated to another straight section. ID32 will most likely not be influenced immediately by the Upgrade Programme.

To explore the opinions and needs of the user community for the upgraded ID01 beamline, a highly successful brainstorming meeting with more than 30 participants was held at the ESRF in November. The diffraction analysis of MEMS/NEMS (micro/nano electro mechanical systems) was recognised as a brand-new and exciting avenue of research. With the novel ESRF in situ AFM at ID01 (see Figure 84), the X-ray analysis of mechanical interaction on the sub-µm scale has already been demonstrated, which may represent another prominent mission for the new ID01 beamline. The other two SIS beamlines had a busy time as well and improvements at ID03 have continued. In the ID03 UHV chamber in EH2, cooling was improved (< 30 K) and a high precision and rigid HEXAPOD for sample alignment with six degrees of freedom has now been installed. In EH1, a new small-volume flow-through reactor for in situ X-ray diffraction was commissioned, which permits rapid gas exchange and thus allows surface reactions to be followed at much increased speed (< sec). At ID32, the X-ray standing wave and photoelectron spectroscopy capabilities have been further upgraded. A new UHV system with a (presently unique) photoelectron analyser was installed in EH2. The analyser for HAXPES (hard X-ray photoelectron spectroscopy) studies is equipped with a low-noise 2D delay-line detector and, once fully commissioned, will permit the analysis of electrons with up to 15000 eV kinetic energy with very high resolution (nominally down to E/E = 10-6). Fresnel zone plates, installed in front of the existing XPS system, have been tested and can deliver a beam as small as 3 µm for spatially-resolved XPS measurements.

Fig. 84: A monochromatic X-ray beam of ~ 9.9 keV is focused by beryllium lenses (CRL) onto a single SiGe island while an atomic force microscopy (AFM) tip is used to apply pressure. A two dimensional image of the scattering close to the SiGe(004) Bragg peak is recorded. The shift in intensity (marked by the green arrows) reflects the compression of the island’s lattice parameter (see http://www.esrf.fr/news/spotlight/spotlight63).

Surface science is dead, yet long live surface science since with the advent of the fashionable term nanoscience, many fields of (classical) surface science underwent some metamorphosis, but mostly in their labelling. However, a real shift in paradigm accompanied the change in the name of our group from surface science to surface and interface science (SIS) some years ago. The change reflected two aspects: firstly, the term surface for the truncated region of a solid suggest a purely two dimensional nature while the region affected by the truncation always extends into the third dimension. Secondly, it is apparent that the trend of science becoming more and more specialised is being reversed at present owing to the increasing interest in more complex systems. Thus, even the classical surface science has become more and more multidisciplinary. Surface scientists are looking at what’s happening above and below where two agents meets, whether these are solid and vacuum, solid and solid, solid and liquid, etc. Contact points or phase boundaries are areas of interaction, interchange, and reaction and affect the properties of the materials involved. This is of interest to almost all fields in natural science and most industries. Noteworthy, the increased interaction extends to the scientists involved as well.

This year’s SIS highlights are clearly testifying toward multidisciplinary interaction. Stadler et al. revealed that the cohesion among organic molecules can be tuned by the adsorption on a metal (silver) surface by using X-ray standing wave (XSW) studies with photoelectron spectroscopy at ID32. Dealing with a similar subject, also on the borderline between physics and chemistry, and likewise using the XSW method at ID32, Koch et al. find that the specific chemical/electronic interaction of molecules with a metal surface can lead to pronounced molecular distortions. The contribution of Le Bolloc’h et al. correlates structure and electronic properties for a subject of fundamental physics. An electronic excitation, a charge density wave, was studied by diffraction at ID01, and the authors discovered that it shows an intriguingly long coherence length of the order of µm. Making important progress toward the future mission of ID01, a joint team from DESY, IKZ Berlin, JKU Linz, and the ESRF (Zozulya et al.) managed to record CDI patterns from sub-µm small SiGe islands and to reconstruct their shape and density by a model-free phase retrieval approach.

While the last four contributions analysed in some detail some of the amazing features that Mother Nature is able to create on surfaces, in the following reports the authors watched over Mother Nature’s shoulder when in action. Thus, Coati et al. observed the detailed nano-faceting of vicinal Ni surfaces induced by Ag deposit. Nolte et al. observe an oxygen-induced shape change of the Rh nanoparticles on a MgO(100) during oxidation and CO induced reduction that turns out to be fully reversible. Finally, in a collaborative effort, a team from MPI Halle, APS/ANL, and the ESRF studied the mesoscopic relaxations in cobalt nano-islands on Cu(001) and found experimental evidence for large contractions of the interatomic cobalt distances. With so many excellent results coming from the SIS beamlines, a selection of a few highlights is always difficult. I hope you enjoy our choice and I wish you a happy reading.

J. Zegenhagen