COADSORBATE INDUCED RECONSTRUCTION OF A STEPPED PT(111) SURFACE BY SULFUR AND CO - A NOVEL SURFACE RESTRUCTURING MECHANISM OBSERVED BY SCANNING-TUNNELING-MICROSCOPY

The chemisorption of sulfur and CO was found to have profound effects on the structure of a stepped platinum surface. By itself, sulfur chem isorbs, forming a p(2 x 2) ordered structure, and induces doubling of the terrace widths and step heights. Subsequent coadsorption of CO dis places the sulfur, compressing it to distances of root 3 times the Pt lattice spacing, and induces surface restructuring; New terraces form which contain exclusively CO and are separated by monatomic steps from the terraces containing the compressed sulfur overlayer. This coadsor bate induced restructuring phenomenon has strong implications in the m echanisms of surface catalyzed reactions.