Adsorption of ethylene on Sn and In terminated Si(001) surface studied by photoelectron spectroscopy and scanning tunneling microscopy (original) (raw)
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Arxiv preprint arXiv: …, 2009
The vibrational and structural properties of a single-domain Si(001)-(2x1) surface upon ethylene adsorption have been studied by density functional cluster calculations and high-resolution electron energy loss spectroscopy. The detailed analysis of the theoretically and the experimentally determined vibrational frequencies reveals two coexisting adsorbate configurations. The majority ethylene species is di-σ bonded to the two Si atoms of a single Si-Si dimer. The local symmetry of this adsorption complex for ethylene saturation is reduced to C 2 as determined by surface selection rules for the vibrational excitation process. The symmetry reduction includes the rotation of the C-C bond around the surface normal and the twist of the methylene groups around the C-C axis. Experimentally 17 ethylene-derived modes are found and assigned for the majority and the minority species based on a comparison with calculated vibrational frequencies. The minority species which can account up to 14 % of the total ethylene coverage is spectroscopically identified for the first time. It is assigned to ethylene molecules di-σ bonded to two adjacent Si-Si dimers (in an end-bridge configuration). One part of these minority species desorbs molecularly at 665 K, about 50 K higher than the majority species, whereas the remaining part dissociates to adsorbed acetylene at temperatures around 630 K. For the latter a di-σ end-bridge like bonding configuration is proposed based on a comparison of the vibrational spectra with data for adsorbed acetylene on Si(100)-(2x1).
Adsorption of ethylene on Si(111)7×7 by synchrotron radiation photoemission
Journal of Electron Spectroscopy and Related Phenomena, 1995
Ethylene adsorption on Si(lll)7x7 was studied by valence band and Si2p core line synchrotron radiation photoemission. Experiments were performed at room temperature, as a function of coverage. The simultaneous quenching of the S 1 and $2 silicon surface states upon adsorption shows that ethylene adsorbs in a molecular form, on a bridging site between a silicon adatom and rest atom. An electron donation from silicon to ethylene, which indicates a rather strong Si-C bond, induces an upward shift of the shallower molecular orbitals. The C-C double bond is stretched and becomes intermediate between single and double bond.
Adsorption of ethylene on Si(111)7x7 by synchrotron radiation photoemission
Ethylene adsorption on Si(lll)7x7 was studied by valence band and Si2p core line synchrotron radiation photoemission. Experiments were performed at room temperature, as a function of coverage. The simultaneous quenching of the S 1 and $2 silicon surface states upon adsorption shows that ethylene adsorbs in a molecular form, on a bridging site between a silicon adatom and rest atom. An electron donation from silicon to ethylene, which indicates a rather strong Si-C bond, induces an upward shift of the shallower molecular orbitals. The CC double bond is stretched and becomes intermediate between single and double bond.
The Journal of Chemical Physics
A detailed first-principles density functional analysis of the geometric and electronic properties of ethylene adsorbed on the dimer reconstructed Si(001)-(2×1) surface is presented. This theoretical study was carried out in close reference to a recent angle-resolved photoemission spectroscopy investigation of the same adsorption system. Adsorbate weighted Kohn-Sham one-particle spectra are calculated and compared to the band structure derived from the angle-resolved photoemission spectra. In addition, the symmetry character of the concomitant Bloch waves is determined to yield information which can directly be related to the results of a dipole selection rule analysis of the corresponding photoemission signals. Total energy minimization of a model slab reveals a distortion of the adsorption complex at saturation coverage to local C2 symmetry involving an 11° rotation of the ethylene molecule around the surface normal and a 27° twist of the methylene groups around the CC axis. This ...
Journal of Physics: Condensed Matter, 2008
Scanned-energy mode C 1s photoelectron diffraction has been used to investigate the local adsorption geometry of benzene on Si(001) at saturation coverage and room temperature. The results show two different local bonding geometries co-exist, namely the 'standard butterfly' (SB) and 'tilted bridge' (TB) forms, with a composition of 58±29% of the SB species. Detailed structural parameter values are presented for both species including Si-C bondlengths. Based on published measurements of the rate of conversion of the SB to the TB form on this surface we estimate that the timescale of our experiment is sufficient to achieve equilibrium, and in this case our results indicate that the difference in the Gibbs free energy of adsorption, (G(TB)-G(SB)), is in the range-0.023 to +0.049 eV. We suggest, however, that the relative concentration of the two species may also be influenced by a combination of steric effects influencing the kinetics, and a sensitivity of the adsorption energies of the adsorbed SB and TB forms to the nature of the surrounding benzene molecules.
The Journal of Chemical Physics, 2010
The vibrational and structural properties of a single-domain Si͑001͒-͑2 ϫ 1͒ surface upon ethylene adsorption have been studied by density functional cluster calculations and high-resolution electron energy loss spectroscopy. The detailed analysis of the theoretically and the experimentally determined vibrational frequencies reveals two coexisting adsorbate configurations. The majority species consist of ethylene molecules which are di-bonded to the two Si atoms of a single Siu Si dimer. The local symmetry of this adsorption complex is reduced to C 2 for ethylene saturation coverage as determined by surface selection rules for the vibrational excitation process. The symmetry reduction includes the rotation of the C u C bond around the surface normal and the twist of the methylene groups around the C u C axis. Experimentally, 17 ethylene-derived modes are found and assigned for the majority and the minority species based on a comparison with calculated vibrational frequencies. The minority species which can account up to 14% of the total ethylene coverage is spectroscopically identified for the first time. It is assigned to ethylene molecules dibonded to two adjacent Siu Si dimers ͑in an end-bridge configuration͒. One part of the minority species desorbs molecularly at 665 K, about 50 K higher than the majority species, whereas the remaining part dissociates to adsorbed acetylene at temperatures around 630 K. For the latter, a diend-bridge like bonding configuration is proposed based on a comparison with vibrational data for adsorbed acetylene on Si͑100͒-͑2 ϫ 1͒. Physics 133, 054705-1 054705-2 Kostov et al. J. Chem. Phys. 133, 054705 ͑2010͒ 054705-6 Kostov et al. J. Chem. Phys. 133, 054705 ͑2010͒ 054705-8 Kostov et al. J. Chem. Phys. 133, 054705 ͑2010͒ 054705-10 Kostov et al.
Adsorption of small hydrocarbon molecules on Si surfaces: Ethylene on Si(001)
Physical Review B, 2008
The interaction between small unsaturated hydrocarbon molecules of C 2 H 4 with a vicinal silicon ͑001͒ surface is studied by means of reflectance anisotropy spectroscopy and analyzed with first principles calculations. Our results confirm that ethylene adsorbs without breaking the silicon dimers. Comparison of theoretical optical spectra with experimental data shows that the C 2 H 4 molecules lay on top of the silicon dimers from low to high coverage. This occurs even though, from a purely energetic point of view, a bridge configuration would be favorable at 1 monolayer coverage.
The Journal of Chemical Physics, 2010
The vibrational and structural properties of a single-domain Si͑001͒-͑2 ϫ 1͒ surface upon ethylene adsorption have been studied by density functional cluster calculations and high-resolution electron energy loss spectroscopy. The detailed analysis of the theoretically and the experimentally determined vibrational frequencies reveals two coexisting adsorbate configurations. The majority species consist of ethylene molecules which are di-bonded to the two Si atoms of a single Siu Si dimer. The local symmetry of this adsorption complex is reduced to C 2 for ethylene saturation coverage as determined by surface selection rules for the vibrational excitation process. The symmetry reduction includes the rotation of the C u C bond around the surface normal and the twist of the methylene groups around the C u C axis. Experimentally, 17 ethylene-derived modes are found and assigned for the majority and the minority species based on a comparison with calculated vibrational frequencies. The minority species which can account up to 14% of the total ethylene coverage is spectroscopically identified for the first time. It is assigned to ethylene molecules dibonded to two adjacent Siu Si dimers ͑in an end-bridge configuration͒. One part of the minority species desorbs molecularly at 665 K, about 50 K higher than the majority species, whereas the remaining part dissociates to adsorbed acetylene at temperatures around 630 K. For the latter, a diend-bridge like bonding configuration is proposed based on a comparison with vibrational data for adsorbed acetylene on Si͑100͒-͑2 ϫ 1͒. Physics 133, 054705-1 054705-2 Kostov et al. J. Chem. Phys. 133, 054705 ͑2010͒ 054705-6 Kostov et al. J. Chem. Phys. 133, 054705 ͑2010͒ 054705-8 Kostov et al. J. Chem. Phys. 133, 054705 ͑2010͒ 054705-10 Kostov et al.
Surface Science, 1998
The core-level binding energies of simple unsaturated organic molecules bonded to the Si(001) surface have been investigated using X-ray photoelectron spectroscopy (XPS). Using the Si 2p levels as an internal standard, the shifts in carbon and nitrogen levels were analyzed for a series of small unsaturated molecules, including cyclopentene, ethylene, acetylene, 3-pyrroline and pyrrolidine, adsorbed on the Si(001) surface. Alkene-like carbon atoms are found to have binding energies 0.6-0.9 eV higher than alkane-like molecules. Carbon atoms bonded directly to the silicon surface show binding energies 0.7-0.8 eV lower than those that are not bonded directly to silicon. The N 1s binding energy is decreased by 0.9 eV by bonding to silicon. The use of XPS for identification of bonding configurations of unsaturated organic molecules on the silicon (001) surface is discussed.