Nature of interface bonding of ethylene and benzene with Si(1 0 0)c(4×2): angle-dependent Si 2p high resolution photoelectron spectroscopy studies

The interface bonding between adsorbates (ethylene and benzene) and the Si(1 0 0)c(4×2) surface has been investigated by means of angle-dependent Si 2p high resolution photoelectron spectroscopy at 140 K, and several new quantitative properties have been obtained. Upon ethylene adsorption, a drastic decrease of up dimer and down dimer atom components (95%), and the appearance of a new component has been observed. This new component is assigned to the outer most Si atoms which are bonded to ethylene. The originally asymmetric Si dimer atoms become chemically equivalent upon adsorption. In the case of benzene, the decrease of up dimer and down dimer components is about 49% at the saturation coverage, and the unreacted dimers remain asymmetric. The charge transfer between adsorbed molecules and the Si(1 0 0)(2×1) surface has been estimated from the core-level shift and the nature of interface bonding including surface and second layer Si atoms is discussed.