VIL D: Surface physics/chemistry and nanosciences (Section 6.2-4 ,page 30, Annex 1)
It should be emphasised that the surface physics aspects of Complex Metallic Alloys are considered a new frontier in solid state physics (Prof. P.A. Thiel, head of the Chemistry Dpt at Ames Laboratories, DOE, USA) and a template for the discovery of a wealth of new interesting surface effects. For many of the potential applications of CMAs, surface properties such as friction, adhesion, corrosion and wear resistance, will determine the performance of the material. Thus, the surface characterisation of CMAs, as well as the determination of preparation-route property relations, is of vital importance for potentially novel applications. Accordingly, VIL D will unite highly experienced process-oriented groups with high-reputation research groups in physics, chemistry and corrosion. R. McGrath (ULIV) and K. Urban (FZJ), who have collected considerable expertise on scanning tunnelling microscopy (STM) of complex metal surfaces will provide UHV STM means, J.M. Dubois (CNRS-N) will provide access to a new platform under construction that will offer simultaneously a bench of preparation techniques (PVD, CVD, electron-beam evaporation, single crystal preparation) coupled in-line with the most modern surface characterisation techniques (XPS, APM, SEM, X-ray spectroscopy) in order to avoid any undesirable contamination of the surface. L. Schlapbach (EMPA) will provide angular resolved XPS, atomic force microscopy and low-temperature STM, including possibilities to look at magnetic properties of adsorbates. V. Pontikis (CNRS-V) will provide LEED, AES and X-ray photoelectron spectroscopy housed in an instrument specially equipped for the study of oxidised metals and their adhesion properties. Finally, adhesion and wetting will be addressed by the study of liquid metal droplets deposited in vacuum at high temperature (D. Chatain, CNRS-M) or organic liquids at ambient temperature (J.M. Dubois, CNRS-N). The research plan of VIL D is subdivided into the following three main tasks:
a) Fundamental studies of clean surfaces (i.e. single crystal surfaces prepared in a ultra-high vacuum) provide an essential underpinning of investigations of both the low dimensional structures and the more technologically relevant "real" surfaces. The goal of studies of these surfaces is to determine their structure, to achieve a precise description of their chemical composition and electronic structure, and to characterise their chemical reactivity and stability when atomic and molecular species are adsorbed. Comparative studies of a number of selected CMAs will be carried out in order to enable the establishment of general principles of CMA surfaces. Of further interest will be oxidation studies under controlled conditions.
b) Low-dimensional structures on CMA surfaces potentially generate possibilities for novel nanotechnology applications exploiting the unusual electronic structure and local symmetries of CMA. This new field will exploit the selforganisation of adsorbed species on well-characterised CMA surfaces to form low-dimensional nanostructures and novel surface alloys (B. Aufray, CNRS-M). Of particular interest will be the study of self-assembled nano-clusters that are expected to nucleate on specific adsorption sites on CMA surfaces (R. McGrath, ULIV) and may then serve as templates for the formation of novel low dimensional structures and nano-scale thin films formed through selforganisation (P. Gas, CNRS-M), and the pursuit of surface alloys with unusual, e.g. magnetic, properties (L. Schlapbach, EMPA). Strong emphasis will be put on realistic computer simulations that participant groups have actually pushed to a very high standard, yet considering simpler structures as those of CMAs (C. Massobrio, CNRS and G. Treglia, CNRS-M)
c) "Real" surfaces (i.e. those exposed to an atmospheric environment and covered with an oxide layer), will play a major role in corrosion resistance (KUL), friction (CNRS-N), adhesion (CNRS-N), and optical properties (KTH). The characteristics of the oxide layer will largely depend on the substrate, and can further vary with time as the material is ageing. A realistic study of the surface properties of ˆ¢’Ǩ‰ìrealˆ¢’ǨÔø‡ CMA materials must hence account for the surface composition of the initial material, the initial oxidation of the surface layers as a function of the initial alloy surface, the properties of the initial oxide layer (surface energy, composition, electronic structure), and the stability of the oxide layer as a function of time. The methodology of such studies will involve preparation of the surface under realistic conditions followed by its transfer, preferably in situ, to a suitable characterisation facility (V. FournˆÉ¬©e, CNRS-N).
