  We present a theory of current conduction through buckyball(C60) molecules on
silicon by coupling a density functional treatment of the molecular levels
embedded in silicon with a non-equilibrium Green's function (NEGF) treatment of
quantum transport. Several experimental variations in conductance-voltage(G-V)
characteristics are quantitatively accounted for by varying the detailed
molecule-silicon bonding geometries. We identify how variations in contact
surface microstructure influence the number, positions and shapes of the
conductance peaks, while varying separations of the scanning probe from the
molecules influence their peak amplitudes.
