IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Surface Science Monday Sessions
       Session SS2-MoP

Paper SS2-MoP16
Dynamics and Thermal Stability of Cs Super-structures on a Pt(111) Surface

Monday, October 29, 2001, 5:30 pm, Room 134/135

Session: Surfaces and Interfaces Poster Session
Presenter: T. Kondo, University of Tsukuba, Japan
Authors: T. Kondo, University of Tsukuba, Japan
H. Kozakai, University of Tsukuba, Japan
T. Sasaki, University of Tsukuba, Japan
S. Yamamoto, University of Tsukuba, Japan
Correspondent: Click to Email
Understanding the dynamics and the thermal stability of alkali-metal atoms adsorbed on a metal surface is essentially important for controlling the monolayer growth and unveiling the origin of the work function reduction due to adsorption. We have made clear the dynamics from formation to destruction and the thermal stability of the Cs super-structures on a Pt(111) surface by means of Helium atom scattering (HAS) which enables us to study at high sensitivity the dynamics of the ultra-thin delicate layer of Cs atoms. Among three structures previously identified by LEED, both the (@sr@3x@sr@3) and the (@sr@3x@sr@3)R30° structures are found unstable and destructed at around 350K, transforming into the more stable (2x2)structure. The (2x2) structure which is stable up to about 450K exhibits a large corrugation of the potential energy surface seen by He atoms. This suggests a strong bond between Cs and Pt atoms and the localization of electron cloud density for the (2x2) structure as a result of the charge transfer from Cs atoms to the substrate Pt(111) surface. It is also suggested that the work function minimum, attained at the Cs coverage 0.25 forming the (2x2) structure, is closely related to this charge transfer. On the contrary, the small corrugation for the (@sr@3x@sr@3) structure at a full coverage indicates that a bond among adsorbed Cs atoms is metallic, the electrostatic potential being delocalized along the direction parallel to the surface.