| 초록 |
By employing ab initio total-energy calculations we have studied the adsorption of 1,3-butadiene molecule(C4H6) on a dimer-reconstructed Si(001) surface. We have found that the [4+2] products are thermodynamically more stable than the [2+2] products Two kinds of stable [4+2] products are found: (i) the well-known on-top di-sigma configuration over a single dimer and (ii) end-bridge([EB]) configuration occupying two successive dimers in the same dimer row. In [EB] configuration at one mono layer (ML) coverage, 1,3-butadiene molecules at opposite end of dimer combine together to form cubane (C8H8)-like square geometry with one hydrogen atom at each apex, which is stabilized by converting remaining pi-bonds to sigma-bonds. The calculated core-level shifts(CLS) of C 1s orbital in stable configurations show little difference between peaks from interface C atom bonded directly to silicon surface and those from surface C atom with unsaturated double bond. We have also simulated the scanning tunnelling microscope(STM) image, which is in good agreement with experimental STM data. |
