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-MoP15
Local Tunneling Barrier Height Measurement of Cs Monolayer on a Pt(111) Surface

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

Session: Surfaces and Interfaces Poster Session
Presenter: Y. Yamada, University of Tsukuba, Japan
Authors: Y. Yamada, University of Tsukuba, Japan
A. Sinsarp, University of Tsukuba, Japan
M. Sasaki, University of Tsukuba, Japan
S. Yamamoto, University of Tsukuba, Japan
Correspondent: Click to Email
The local tunneling barrier height (LBH) image of the Cs monolayer on a Pt(111) surface is measured in atomic resolution by means of an STM technique. The Cs atoms form three different superstructures, (2x2), (@sr@3x@sr@3) and (@sr@3x@sr@3)R30, depending on its surface coverage on the Pt(111) surface. We find that the (2x2) structure is thermally stable at room temperature in contrast to other structures which disappear in few hours. Only for the (2x2) structure, we could obtain a clear atom-resolved STM/LBH image at room temperature. We find the atomic LBH distribution in the image corresponding to atomic geometry of this structure. This distribution, however, cannot be considered to be identical to the distribution of the classically defined work function. The average barrier height of this structure is, however, about 2.2eV smaller than that of a clean Pt(111) surface, suggesting the work function reduction of about 4.4eV from the clean Pt(111) value. This agrees well with our macroscopical work function results measured by means of the Kelvin contact potential method. The (2x2) surface corrugation amplitude obtained from the STM image is as large as 0.6Å, suggesting that the spatial distribution in the electron density of this structure is strongly localized, in contrast to the case of other 'metallic' superstructures, where no atomic image is observed by STM. It is speculated that the charge localization with some charge transfer causes the lowest work function of the (2x2) structure and its high thermal stability.