Initial adsorption structure of ethylene on Si(001) surface at room temperature

Ethylene (C2H4) on the Si(001) surface has been a Subject of numerous investigations over a decade. Despite a wealth of experimental and theoretical studies, the adsorption structures are not clearly understood yet. In order to elucidate this controversial issues clearly, C2H4 molecules have been non-dissociatively chemisorbed on Si(001)-(2 x 1) surface at room temperature with an exposure of 100 L, and C2H4 on Si(001) surface structure has been investigated by coaxial impact collision ion scattering spectroscopy (CAICISS). To determine the adsorption structure of the C2H4 molecules definitely, the computer simulation with the two-dimensional trajectory counting method has been performed for the recently proposed most possible two single molecular adsorption configurations (di-sigma on-top and di-sigma end-bridge). The CAICISS spectra show a better agreement with the simulation results for the di-sigma on-top structure than that for the di-sigma end-bridge structure. The bond length of Si dimer separation on the Si(001) surface with the adsorption of 100 L C2H4 is found to be 2.35 +/- 0.05 angstrom. This implies that the bonding of Si dimers stays intact. It is also found that the bonding length of C-Si and C-C is 1.81 +/- 0.05 angstrom and 1.61 +/- 0.05 angstrom respectively. (c) 2005 Elsevier B.V. All rights reserved.