title: Quantum tunneling enabled self-assembly of hydrogen atoms on Cu(111).
abstract: Atomic and molecular self-assembly are key phenomena that underpin many important technologies. Typically, thermally enabled diffusion allows a system to sample many areas of configurational space, and ordered assemblies evolve that optimize interactions between species. Herein we describe a system in which the diffusion is quantum tunneling in nature and report the self-assembly of H atoms on a Cu(111) surface into complex arrays based on local clustering followed by larger scale islanding of these clusters. By scanning tunneling microscope tip-induced scrambling of H atom assemblies, we are able to watch the atomic scale details of H atom self-assembly in real time. The ordered arrangements we observe are complex and very different from those formed by H on other metals that occur in much simpler geometries. We contrast the diffusion and assembly of H with D, which has a much slower tunneling rate and is not able to form the large islands observed with H over equivalent time scales. Using density functional theory, we examine the interaction of H atoms on Cu(111) by calculating the differential binding energy as a function of H coverage. At the temperature of the experiments (5 K), H(D) diffusion by quantum tunneling dominates. The quantum-tunneling-enabled H and D diffusion is studied using a semiclassically corrected transition state theory coupled with density functional theory. This system constitutes the first example of quantum-tunneling-enabled self-assembly, while simultaneously demonstrating the complex ordering of H on Cu(111), a catalytically relevant surface.
authors.affiliation: Chemistry Department, Tufts University, 62 Talbot Avenue, Medford, Massachusetts 02155, United States.
authors.forename: April D
authors.initials: AD
authors.lastname: Jewell
authors.forename: Guowen
authors.initials: G
authors.lastname: Peng
authors.forename: Michael F G
authors.initials: MF
authors.lastname: Mattera
authors.forename: Emily A
authors.initials: EA
authors.lastname: Lewis
authors.forename: Colin J
authors.initials: CJ
authors.lastname: Murphy
authors.forename: Georgios
authors.initials: G
authors.lastname: Kyriakou
authors.forename: Manos
authors.initials: M
authors.lastname: Mavrikakis
authors.forename: E Charles H
authors.initials: EC
authors.lastname: Sykes
mesh_terms: D003198:Computer Simulation; D003300:Copper / Q000737:chemistry*; D003460:Crystallization / Q000379:methods*; D006859:Hydrogen / Q000737:chemistry*; D008422:Materials Testing; D008956:Models, Chemical; D011789:Quantum Theory; D012666:Semiconductors
chemical_list: D003300:Copper; D006859:Hydrogen