ROOM-TEMPERATURE REPOSITIONING OF INDIVIDUAL C-60 MOLECULES AT CU STEPS - OPERATION OF A MOLECULAR COUNTING DEVICE

C-60 molecules absorbed on a monoatomic Cu step have been reversibly r epositioned st room temperature with the tip of a scanning tunneling m icroscope by performing controlled displacements along the step direct ion. We demonstrate the feasibility of building an abacus on the nanom eter scale using single molecules as ''counters,'' Cu monoatomic steps as ''rods'' that constrain the molecular motion to one dimension, and the scanning tunneling microscope as an ''actuator'' for counting ope rations. (C) 1996 American Institute of Physics.