C-60 MANIPULATION AND CLUSTER FORMATION USING A SCANNING TUNNELING MICROSCOPE

We have used the tip of an ultrahigh vacuum scanning tunneling microsc ope to induce displacements of C-60 molecules on the Si(111)-7 x 7 sur face at room temperature. The manipulation is achieved by using a swee ping procedure we have developed which moves the tip closer to the sur face and sweeps it across in a predetermined direction. Feedback contr ol of the tunnel current is maintained throughout and the tip-surface separation is adjusted by changing the sample bias and tunnel current. For a 0.007 monolayer (ML) coverage of C-60, a sweeping area of 60 An gstrom x 60 Angstrom was used to move individual C-60 molecules, while for higher coverages (0.05-0.2 ML) a sweeping area of 216 Angstrom x 216 Angstrom was used to move large groups of C-60 molecules. We show an example at 0.2 ML coverage where we have removed C-60 over an area 110 Angstrom x 370 Angstrom resulting in the formation of a line of C- 60 molecules 20-30 Angstrom in width. (C) 1996 American Vacuum Society .