With a nominal diameter of 7 Angstrom of the C60 "football"-molecule, STM is well suited to resolve the intra-molecular structure. There have been several examples in the past (see e.g. Ref.1.), showing STM images with six-fold, four-fold, three-fold and two-fold characteristics. They are not due to single carbon atoms within the molecule, but stem from the benzene-like ring structures (Ref.2), with a strong dependence on the orientation of the C60 molecule with respect to the substrate surface.
With our low-temperature STM, we were able to produce STM images of single C60 molecules adsorbed on Au(110)1x2 at T = 5 K. The STM image shows two such molecules, recorded from the Au(110)1x2 surface with submonolayer C60 coverage. The upper one has an orientation with the hexagonal ring at the top, (corresponding to image type I in Ref. 1), while the lower one is tilted upward by about 15 degrees. The red line reflects the line scan shown below with a detailed corrugation structure. The STM image corresponds to 2.4 nm x 3.4 nm and was measured with tunneling parameters: sample voltage: +0.366 V, current setpoint: 0.173 nA. (data from diploma thesis M. Pollmann)
References:
- R. Gaisch, R. Berndt, J. K. Gimzewski, B. Reihl, R. R. Schlittler, W. D. Schneider, and M. Tschudy, Appl. Phys. A 57, 207 (1993), and references therein
- C. Chavy, C. Joachim, and A. Altibelli, Chem. Phys. Lett. 214, 569 (1993).
