Initial adsorption structure of ethylene on Si(0 0 1) surface at room temperature

Ethylene (C₂H₄) on the Si(0 0 1) 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, C ₂H₄ molecules have been non-dissociatively chemisorbed on Si(0 0 1)-(2 × 1) surface at room temperature with an exposure of 100 L, and C₂H₄ on Si(0 0 1) 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-σ on-top and di-σ end-bridge). The CAICISS spectra show a better agreement with the simulation results for the di-σ on-top structure than that for the di-σ end-bridge structure. The bond length of Si dimer separation on the Si(0 0 1) surface with the adsorption of 100 L C₂H₄ is found to be 2.35 ± 0.05 Å. 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 Å and 1.61 ± 0.05 Å respectively.