Adsorbate-induced alloy phase separation: a direct view by high-pressure scanning tunneling microscopy.
The influence of high pressures of carbon monoxide (CO) on the stability of a Au/Ni(111) surface alloy has been studied by high-pressure scanning tunneling microscopy. We show that CO induces a phase separation of the surface alloy at high pressures, and by means of time-lapsed STM movies we find that Ni atoms are removed from the surface layer during the process. Density functional theory calculations reveal the thermodynamic driving force for the phase separation to be the Au-induced compression of the CO overlayer with a resulting CO-CO repulsion. Furthermore, the atomistic mechanism of the process is shown to be kink-site carbonyl formation and evaporation which is found to be enhanced by the presence of Au.
Vestergaard
Ebbe K
EK
Interdisciplinary Nanoscience Center (iNANO) and Department of Physics and Astronomy, University of Aarhus, DK 8000 Aarhus C, Denmark.
Vang
Ronnie T
RT
Knudsen
Jan
J
Pedersen
Thorbjørn M
TM
An
Toshu
T
Laegsgaard
Erik
E
Stensgaard
Ivan
I
Hammer
Bjørk
B
Besenbacher
Flemming
F