| Autor: |
Tetlow H; Physics Department, King's College London, London, WC2R 2LS, UK. lev.kantorovitch@kcl.ac.uk., Posthuma de Boer J; The Blackett Laboratory, Imperial College London, London SW7 2AZ, UK., Ford IJ; Department of Physics and Astronomy and London Centre for Nanotechnology, University College London, Gower Street, London WC1E 6BT, UK., Vvedensky DD; The Blackett Laboratory, Imperial College London, London SW7 2AZ, UK., Curcio D; Physics Department, University of Trieste, Via Valerio 2, 34127 Trieste, Italy., Omiciuolo L; Physics Department, University of Trieste, Via Valerio 2, 34127 Trieste, Italy., Lizzit S; Elettra - Sincrotrone Trieste S.C.p.A., AREA Science Park, S.S. 14 km 163.5, 34149 Trieste, Italy., Baraldi A; Physics Department, University of Trieste, Via Valerio 2, 34127 Trieste, Italy and Elettra - Sincrotrone Trieste S.C.p.A., AREA Science Park, S.S. 14 km 163.5, 34149 Trieste, Italy and IOM-CNR, Laboratorio TASC, AREA Science Park, S.S. 14 km 163.5, 34149 Trieste, Italy., Kantorovich L; Physics Department, King's College London, London, WC2R 2LS, UK. lev.kantorovitch@kcl.ac.uk. |
| Abstrakt: |
The complete mechanism behind the thermal decomposition of ethylene (C 2 H 4 ) on Ir(111), which is the first step of graphene growth, is established for the first time employing a combination of experimental and theoretical methods. High-resolution X-ray photoelectron spectroscopy was employed, along with calculations of core level binding-energies, to identify the surface species and their evolution as the surface temperature is increased. To understand the experimental results, we have developed a reaction sequence between the various C n H m species, from ethylene to C monomers and dimers, based on ab initio density functional calculations of all the energy barriers and the Arrhenius prefactors for the most important processes. The resulting temperature evolution of all species obtained from the simulated kinetics of ethylene decomposition agrees with photoemission measurements. The molecular dissociation mechanism begins with the dehydrogenation of ethylene to vinylidene (CH 2 C), which is then converted to acetylene (CHCH) by the removal and addition of an H atom. The C-C bond is then broken to form methylidyne (CH), and in the same temperature range a small amount of ethylidyne (CH 3 C) is produced. Finally methylidyne dehydrogenates to produce C monomers that are available for the early stage nucleation of the graphene islands. |
