title: Orthogonal Intermolecular Interactions of CO molecules on a one-dimensional substrate.
abstract: By low-temperature scanning tunneling microscopy, we study CO molecule chemisorption on a quasi-one-dimensional Cu(110)-(2×1)-O surface. Atom-resolved images reveal how the interaction of CO with the surface Cu-O- chains gives rise to orthogonal attractive and repulsive intermolecular interactions. First-principles calculations show that CO molecules induce unprecedented lifting of the host Cu atoms by 1 Å from the Cu-O- chains, enabling the Cu-CO unit to tilt by 45° from the surface normal. Contrary to the behavior of CO on metal surfaces, this structural distortion enables unprecedented, orthogonal, short-range intermolecular dipole-dipole attraction and long-range, surface-mediated repulsion. These interactions lead to self-assembly into molecular nanograting structures consisting of arrays of single-molecule-wide CO rows. The origin of the novel behavior of CO molecules in the electronic and geometrical properties of the quasi-one-dimensional substrate suggests that similar molecule-molecule and molecule-substrate interactions could play an important role at catalytic sites on reactive surfaces.
authors.affiliation: Department of Physics and Astronomy, University of Pittsburgh, Pennsylvania 15260, USA.
authors.forename: Min
authors.initials: M
authors.lastname: Feng
authors.forename: Chungwei
authors.initials: C
authors.lastname: Lin
authors.forename: Jin
authors.initials: J
authors.lastname: Zhao
authors.forename: Hrvoje
authors.initials: H
authors.lastname: Petek