Scanning Tunneling Microscopy/Spectroscopy Studies of Lanthanum Endohedral Metallofullerenes

We have investigated monolayer and multilayer islands of La 2 @C 80 and La@C 82 molecules grown on a hydrogen-terminated Si(100)-2 × 1 surfaces by ultrahigh vacuum scanning tunneling microscopy. The observed La 2 @C 80 molecule has a spherical shape, consistent with a recent result by synchrotron X-ray measurements. The energy gap for the La 2 @C 80 multilayer islands is measured to be 1.3−1.5 eV, whereas that for La@C 82 is 0.5 eV, indicating that the I h cage of the La 2 @C 80 molecule is highly stabilized by an electron transfer from the encaged La atoms.