Incomplete wetting of very dilute Cu(Ag) alloys by surface segregation

A350

656 Surface Science 25 t/'252 ( 1 t~91 ) 656 65t~ N,~rth-Holland

Roughening phenomena at the Au(ll0) surface U. R o m a h n ~, H. Z i m m e r m a n n b, M. Nold ~, A. Hoss ", H. G6bet b, P. von Blanckenhagen ~' and W. Schommers b " lnstitut fiir Nukleare Festk6rperphysik, t, and lnstttut fiir Material- und Festki~rperforschung, Kernforschungszentrurn Karl~ruhe. ostfach 3640, W-7500 Karlsruhe, Germany

Received 1 October 1990; accepted for publication 3 Janua~ 1991

The temperature dependence of the structure of the Au( l l0) surface has been studied between 510 and 713 K sample temperature by LEED experiments. A strong broadening of the 23 eV specular reflex was found indicating that the surface becomes rough already below the order-disorder transition. At T > T~. the peak width increases much faster with temperature up to 703 K where we observed a sudden change of the energy spectra.

660

Origin of the surface core-level of the W( 100} surface K.G. Purcell Surface Science Centre, University of Lwerpool, Liverpool L69 3BX, UK

J. Jupille Laboratoire Maurice Letort, 54600 Villers-Les-Nancy, France

and D.A. King Department of Chemistry, University of Cambridge, Cambridge CB2 IEW, UK

Received 1 October 1990; accepted for publication 24 November 1990

Surface Science 251/252 (t991) 660-663 North-Holland

shifts induced by reconstruction

The clean, H-induced and N-induced reconstructions of the W(100} surface have been studied by means of surface core-level spectroscopy. The clean and N-induced SCL shifts are consistent with a simple, local restructuring of the surface layer. The surprising case of the hydrogen reconstruction, involving an anomalous SCL shift to the higher binding energy side of the bulk peak, is discussed.

664 Surface Science 251/252 (1991) 664-669 North-Holland

Incomplete wetting of very dilute Cu(Ag) alloys by surface segregation J. Eugene a, G. Tr~glia b, B. Legrand c, B. Aufray ~ and F. Caban~ a " Laboratoire de M~tallurgie, Facultd des Sciences et Techniques de St-Jdrome, Boite 511, 13397 Marseille Cedex 13, France h Laboratoire de Physique des Solides, Universit$ Paris-Sud, Batiment 510, 91405 Orsay Cedex, France ' Section de Recherches de M$tallurgie Physique, CEN Saclay, 91191 Gif-sur-Yvette Cedex, France

Received 1 October 1990; accepted for publication 3 January 1991

The equilibrium segregation isotherm derived from kinetics experiments on a dilute Cu(Ag) solid solution exhibits at T = 730 K a surface phase transition from almost pure Cu to almost pure Ag. The energetics of the driving forces being unambiguously defined from the electronic structure (TBIM: tight-binding lsing model), this transition can be easily interpreted in the framework of a simplified (Fowler-Guggenheim type) approach. A more sophisticated statistical treatment (APM: area preserving mapping) shows that this transition should be first of a finite succession of layering transitions leading to an incomplete Ag-wetting of the Cu(Ag) surface.