Scanning tunneling microscopy images for two isomers of Ce@C82 were observed on Si(111)-(7X7) at 295 K. The Ce@C82 molecules in the first layer were bound to the Si surfaces, and the motions were frozen even at 295 K. The multilayer of the Ce@C82 isomer I (Ce@C82-I) produced a close-packed structure in the surface layer by annealing the Si substrate at 473 K. The distance between the nearest-neighboring molecules was 1.15(4) nm whose value was consistent with that, 1.12 nm, estimated from x-ray diffraction of the Ce@C82-I crystals. This implies that the close-packed structure is dominated by van der Waals forces, as in crystals of Ce@C82-I. The internal structure of Ce@C82-I was observed in the first layer due to a freeze of molecular motion caused by strong interactions between the molecule and the Si adatoms in the surface. Scanning tunneling spectroscopy revealed that the energy gaps for Ce@C82-I and -II in the first layer opened to gap energies, Eg of 0.7 and 1.0 eV, respectively. This fact suggests that these molecules are semiconductors with smaller value of Eg than those for C60 and C70.
|Number of pages||7|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - Dec 1 2004|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics