Manipulation The Orientation Of Individual Fullerene On Si Surface At Room-temperature

The orientations of individual fullerene molecules adsorbed on Si(111)-(7x7) havebeen successfully obtained by scanning tunneling microscopy at room temperature.There are two equivalent adsorption geometries for "Hexagon" fullerene molecules,and three equivalent adsorptions for "6-6bond" fullerene molecules based on highresolution STM images. In the case of "5-6bond" fullerene, twelve equivalentin-plane orientations have been clearly observed. The orientations of “5-6bond”fullerene molecules can be rotated by integral times as30degree when a pulse bias isapplied between the STM tip and the certain sites within the molecule. Theachievement of continuous manipulation on a molecule shows that reversiblemolecular switches with molecular orientation as the information carrier have beenrealized on individual fullerene molecules adsorbed on Si(111) surface at roomtemperature.The dependences of the molecular rotation probability on the bias between the tipand the molecule, the process of applied bias and the tip-sample distance have beeninvestigated on many manipulation cases. Combined with the experimentalobservations and the theoretical analysis, we propose that the rotation of a fullerenemolecule takes place in two successive steps: the bonding between the fullerene andthe Si surface is firstly weakened via electronic excitation and then low energyelectron bombardment causes the molecule to rotate by certain degree.