Electronic structures of layered C₆₀ and C₇₀ on Si(100) surface

Two-dimensional band structure calculation is carried out for the c(4 x 3) C₆₀ and perfect triangular C₇₀ lattices by using a mixed-basis approach in which wave functions are expanded with not only plane waves but also the Is and 2p atomic orbitals of carbon atoms. The effect of the Si(100) substrate is taken into account by simply assuming a charge transfer from Si dimers and a positive charge back-ground. Wave functions of excess charge on these microclusters are analyzed, and the resulting partial charge distributions explain the electron cloud images observed recently with scanning tunneling microscopy (STM).