The Mediation With Ag Cluster For Adsorption State Of Fullerene At Room-Temperature

High-resolution scanning tunneling microscopy (STM) images unambiguouslyreveal that the steadily adsorbed fullerene molecules on Si(111)-7×7reconstructionsurface at room-temperature undergo spontaneously circular transformation amongfive types of adsorption orientations after introducing Ag clusters to the surface. Thefive types of adsorption orientations contain: one of the hexagons facing toward the Sisurface on the corner hole; one of the edge atoms facing down toward the Si surfaceon the middle of defective unit; a pentagon facing toward the surface on the middle ofnon-defective unit;5-6bonds within the molecule faces toward the surface on thecorner of the defective unit and6-6bonds within the molecule faces toward thesurface on the corner of non-defective unit. Most of adsorption orientation transitionsare between one of the edge atoms facing down toward the Si surface and5-6bondswithin the molecule faces toward the surface, or between6-6bonds within themolecule faces toward the surface and5-6bonds within the molecule faces toward thesurface. Reversing the deposition order, i.e., fullerene molecules were adsorbed onSi(111)-7×7surface pre-modified with Ag clusters leads to the same phenomenonshown by high resolution STM images. In contrast, fullerene molecules adsorbed onthe clean bare Si(111)-7×7surface reside on the surface steadily and never shows noadsorption orientation transformation. The Contrast experiments above reveal asignificant role of Ag clusters in adsorption orientations transformation of fullereneadsorbed on Si(111)-7×7surface.Using linescan function of STM system to manipulate fullerene moleculesadsorbed on the bare Si(111)-7×7surface and then monitor their adsorptionorientations, we find that steadily adsorbed fullerene molecules will move slightlywithin a unit of Si(111)-7×7reconstruction surface by applying a certain voltage andcurrent in linescan manipulation. Moreover, the adsorption orientations of thesefullerenes transform simultaneously with its movement by manipulation.