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

Paper SS2-WeA8
Ordered Structures of CO on Pd(111) Studied by STM

Wednesday, October 31, 2001, 4:20 pm, Room 121

Session: Adsorption on Metal Surfaces
Presenter: M.K. Rose, Lawrence Berkeley National Laboratory and University of California at Berkeley
Authors: M.K. Rose, Lawrence Berkeley National Laboratory and University of California at Berkeley
J.C. Dunphy, Lawrence Berkeley National Laboratory
T. Mitsui, Lawrence Berkeley National Laboratory
A. Borg, Norwegian University of Science and Technology, Norway
D.F. Ogletree, Lawrence Berkeley National Laboratory
M. Salmeron, Lawrence Berkeley National Laboratory
Correspondent: Click to Email
The @sr@3x@sr@3-R30°, c(4x2), and (2x2)-3CO structures of CO on Pd(111) have been studied by STM. Shifts of the CO binding site with increasing coverage are observed. At coverages of 1/3 ML and below, CO occupies three-fold hollow sites. Near 1/2 ML, regions of c(4x2) CO with both FCC and HCP three-fold hollow site occupation coexist with bridge bonded c(4x2) CO. At high coverage, a partially disordered phase with no top site occupation directly precedes formation of the 2x2 structure. With additional adsorption of CO, bright maxima appear with 2x2 periodicity. The maxima at the edge of 2x2 domains exhibit a quasi-continuous range of corrugation, implying a gradual shift of CO to top sites. The high corrugation of top site CO obscures the other two CO molecules per unit cell, resulting in a symmetric 2x2 periodicity. In addition to this symmetric 2x2 structure, previously unreported domains of lower symmetry 2x2 are observed.