论文部分内容阅读
The description of the chemical adsorption is of fundamental importance for understanding the catalytic reactions on surfaces and interfaces.The adsorption of CO molecules on metal surfaces has over the years become the prototype system for describing molecular chemisorption.Perennial interest reveals that a complete understanding regarding the fundamental aspects of the molecule-substrate and molecule-molecule interactions, which are responsible for the catalytic chemistry of this comparatively simple molecule, is still far from complete.In this work we report an unique adsorption structure for CO adsorption on Cu(110)-(2×1)-O (Cu(110)-O) reconstructed surface.Combing low temperature scanning tunneling microscope (LT-STM), density functional theory (DEF) and model calculations, we have studied the chemisorption of CO molecules on Cu(110)-O surface.The substrate consists of nearly perfect-Cu-O-chains running in the <001> direction over the entire terrace widths.The one-dimensional nature of the substrate makes possible strongly anisotropic molecule-substrate and molecule-molecule interactions.We have established that adsorption of CO molecules induces a strong distortion of the substrate, i.e.the host Cu atom is lifted by about 0.1 nm from its initial position upon CO adsorption.This behavior is in contrast to CO adsorption on metal surfaces where the host metal atoms are pulled by at most 0.02 nm from their unperturbed positions.In addition, the entire Cu-CO unit tilts by 45°from the surface normal in direction orthogonal to the direction of-Cu-O-chains; such distortion facilitates dipole-dipole attraction among CO molecules leading to formation of CO lines orthogonal to-Cu-O-chains.Moreover, the same distortion causes long-range substrate-mediated repulsion between CO molecules adsorbed on the same-Cu-O-chains.Therefore, at 77K, CO molecules self-assemble into a homogeneous CO grating on Cu(110)-O surface through the orthogonal moleculemolecule and molecule-surface interactions.We describe the electronic and chemical interactions,which lead to this anisotropic molecular self-assembly on a one-dimensional surface.