SEXAFS STUDIES OF SULFUR ADSORBED ON A NICKEL STEPPED SURFACE

The surface structure of (square-root 3 x square-root 3)R30-degrees S/Ni(7 9 11) was investigated at room temperature by the SEXAFS method. We found that the mixture of the step 4-fold site and terrace 3-fold hollow site could explain the observed polarization dependence of the EXAFS amplitude successfully. It should be noted that a (square-root 3 x square-root 3)R30-degrees LEED pattern can be observed only at low temperature for S adsorption on Ni(111). Present results suggest that the S atoms adsorbed on the step 4-fold site play an important role on stabilizing the S atoms on the terrace site, which yield the (square-root 3 x square-root 3)R30-degrees LEED pattern.