Electronic and structural properties of C₅₉Si on the monohydride Si(100) surface

Abstract

ABSTRACT:We propose the use of the Si atom in the C 59 Si molecule as a possible way to controllably anchor fullerene molecules on an Si surface, due to the formation of a strong bond to one of the Si surface atoms. We considered a monohydride Si(100) surface with the H removed from one of the Si surface atoms, and the C 59 Si was adsorbed at this site. Through ab initio calculations based on Density Functional Theory, we obtained a final Si surface -Si C59Si bond distance of 2.37 Å, and a binding energy of -3.0 eV. Considering the reaction H surface ϩ C 59 SiH 3 (C 59 Si) adsorbed ϩ (H 2 ) gas , we find this process to be exothermic by 0.41 eV. Upon adsorption of an isolated molecule, we find four levels in the gap, three empty and one singly occupied, all of them being basically localized at the C 59 Si molecule.

C59Si on the Monohydride Si(100):H−(2 × 1) Surface

“…The final Si(surface)−Si(C 59 Si) bond distance is 2.37 Å. This value is identical to what was obtained previously with non-spin-polarized calculations . Our calculations give for the pure hydrogenated Si(100) surface a Si−Si dimer interatomic distance of 2.43 Å, a Si−H distance of 1.51 Å, and a Si−Si back-bond distance of 2.37 Å.…”

“…There are two types of C−C and C−Si bonds in the C 59 Si fullerene: the ones between two hexagons, which will be labeled as HH, and the ones between a hexagon and a pentagon, which will be labeled as HP. The C−C (HH) and the C−C (HP) are both very similar to the equivalent distances in the pure C 60 and in the isolated C 59 Si and C 59 SiH molecules .…”

“…The C−C (HH) and the C−C (HP) are both very similar to the equivalent distances in the pure C 60 and in the isolated C 59 Si and C 59 SiH molecules . The binding energy, E b 1H , for the C 59 Si molecule to the surface is 2.07 eV, defined as where E T (Si(100):H + C 59 Si ) is the total energy for the configuration with the C 59 Si molecule adsorbed on the monohydride Si(100):H−(2 × 1) surface and E T (C 59 Si) and E T (Si(100):H) 1H are the total energies for the isolated C 59 Si molecule and the monohydride Si(100):H−(2 × 1) system with one hydrogen removed, respectively.…”

“…For the isolated C 59 Si, however, as there is a symmetry reduction, there is a lifting of the C 60 HOMO and LUMO degeneracies. The five C 60 degenerate HOMO orbitals split in four closely spaced levels and another one at a higher energy of approximately 0.1 eV . The three C 60 LUMO levels now result in two closely spaced levels and another one at a lower energy of approximately 0.3 eV.…”

“…A consequence of this band structure is that the system has a nonzero total spin, as it also occurs for the isolated C 59 SiH molecule . From the majority (spin up) and minority (spin down) charge densities, ρ ↑ ( r ) and ρ ↓ ( r ), respectively, we can obtain the net local magnetization m ( r ) = ρ ↑ ( r ) − ρ ↓ ( r ).…”