Adsorption of acetylene and ethylene on the Si(001)2×1 surface studied by NEXAFS and UPS

Abstract The adsorption of acetylene (C 2 H 2 ) and ethylene (C 2 H 4 ) on the Si(001)2×1 surface has been investigated by near edge X-ray adsorption fine structure (NEXAFS) and ultraviolet photoemission spectroscopy (UPS) using synchrotron radiation. Upon molecular adsorption, a drastic decrease of the π* resonance (C 2 H 4 ) and an energy shift of the σ* resonance (both C 2 H 2 and C 2 H 4 ) were observed in the NEXAFS spectra. The intensity of dangling bond states of Si in the UPS spectra diminished significantly by adsorption of both molecules. These results provide firm evidence for the structure model with Si dimers preserved and the di-σ bonding between the adsorbed molecules and Si dimers.