INVESTIGADORES
ASCOLANI Hugo Del Lujan
congresos y reuniones científicas
Título:
Detection of Cu Vacancies During the Phase Transition of the 0.5 ML Sn/Cu(001) Surface Alloy by Direct Recoil Spectroscopy
Autor/es:
J.E. GAYONE; A. CARRERA; O. GRIZZI; S. BENGIÓ; E.A. SÁNCHEZ; J. MARTÍNEZ BLANCO; E.G. MICHEL; J. FUHR; H. ASCOLANI
Lugar:
KIoto
Reunión:
Conferencia; ICACS-25 25th International Conference on Atomic Collisions in Solids; 2012
Resumen:
Atoms deposited on metal surfaces may form islands sitting above the top substrate layer or they may substitute some atoms to form a surface alloy. Formation of a surface alloy implies the movement of many atoms, often leading to surface reconstruction and or vacancy creation. Direct detection of vacancies is important to understand the surface behavior but usually it represents a difficult task for most surface techniques. This is not the case in ion scattering at surfaces since a missing atom implies an extension of the interatomic distances and therefore a reduction in either the shadowing or the blocking critical angle, so by tuning the azimuthal and incidence angles appropriately one can obtain a backscattering signal or a recoiling signal that appears only if a vacancy has been created (Figure 1). In this work we use these effects to characterize the line of vacancies formed by the adsorption of Sn on the Cu(100) surface. In addition, we follow the evolution of these vacancies during the reversible crystallographic phase transition of the 0.5 ML Sn/Cu(100) taking place around 360 K, (3R2xR2)R45° ->(R2xR2)R45°.Combining this technique with MC simulations, we conclude that the high-temperature phase is disordered. The phase transition can therefore be characterized as an order-disorder transition driven by the Cu vacancies entropy.