Adsorption and Wetting Structures of Kr on Pt(111) at 8 K and 45 K Studied by Scanning Tunneling Microscopy

Abstract

Adsorption and wetting structures of Kr on Pt(111) were studied using scanning tunneling microscopy. The characteristics were different from those of Xe/Pt(111) and Xe/Cu(111). At 8 K, Kr atoms adsorbed on terraces and preferential adsorption to step edges was not observed. Kr atoms were imaged with 0.12 nm height and 1.0 nm full width at half maximum. With the additional exposure, adsorption at step edges occurred, with a slight preference for the upper step edges. However, no evidence for the characteristic properties, such as repulsive interaction between adsorbates or modification of the electronic structures at step edges, was observed. With the rise in temperature to 45 K, Kr atoms on the terraces increased in size with hexagonal shape, and wetting of the step edges began. In the wetting process, the lower step edge was more preferential, and the wetting region on both step edges grew with a stripe shape; the edge of the wetting region was not irregular but straight and parallel to the steps. In addition, the height of the Kr images decreased and showed two different values, namely, Kr stripes grown from the lower step edges were observed to have 0.10 nm height, 0.02 nm higher than those with a height of 0.08 nm grown on terraces or at upper step edges. The obtained results indicate the existence of two different structures, which may be attributed to the two structures previously observed by the macroscopic analyses.