SCANNING TUNNELING MICROSCOPY OF C-60 ON GRAPHITE

Scanning tunneling microscopy investigation shows that C60 molecules adsorbed on graphite tend to form clusters of different sizes, which often further aggregate to form massive stacks. Occasionally, the molecules can form quasi-close-packed monolayer structures in small areas. From these areas, with low bias voltages and high tunnel currents we have obtained STM images of C60 molecules, which have the highest resolution and contain the richest structural features, in comparison with those C60 images obtained in previous works. The success of obtaining those low-bias images indicates that those molecules had electronic states around E(F). This fact together with the fact that the C60 molecules imaged in the high resolution images were not rotating imply that the graphite substrate may have strong interaction with C60 molecules. We believe that those atomic-scale features are closely related to the intramolecular structure of C60, even though to interpret them in terms of the molecular structure needs further investigation.