Low‐Energy Electron Diffraction

Abstract

Low‐energy electron diffraction (LEED) is a common and powerful method for determining the geometric structure of solid surfaces. It has the advantage of being fast and inexpensive relative to many other surface techniques. LEED can provide quick information on the surface unit cell size and geometry of single crystal surfaces, and with more effort can be used to determine the complete surface geometry, i.e. composition, bond lengths and angles. Although LEED has been used primarily as a structural technique, it can be used to determine other surface properties such as atomic and molecular vibration and libration amplitudes and energies. LEED has dominated the study of surface geometries for relatively simple structures, and is expected to become increasingly important in the study of nanostructures, molecular adsorbates, and insulating surfaces.

Inelastic H-Atom scattering from ultra-thin films

“…Due to the binding of the surface atoms the surface is in most of the cases more rigid, indicating that the incoming atom experience collisions with a surface atom of an higher effective mass. Experiments of Ar atoms scattered from Pt (111) showed that better agreements with binary collision models are obtained when the surface mass increases to M = 2.5 • M Pt (with M Pt mass of a single platinum atom). [35] 2.1.2 Born-Oppenheimer approximation (BOA)…”

“…The methodology will subsequently extended to insulating surfaces such as Al 2 O 3 as well as ultra thin films of alumina on a platinum substrate. Finally, inspired by the previous studies of free standing graphene on Pt (111) by Hongyang Jiang, [29] the last chapter will deal with hydrogen scattering experiments performed on an atomically thin graphene layer on Ni (111). This chapter will answer the question of how the different nature of a metal surface influences the reactivity of the adsorbed graphene substrate.…”

“…In this thesis, experiments were performed on single crystalline gold, platinum, silver, palladium, nickel and copper metal surfaces at a (111) surface cut as well as on a single crystalline insulting α-Al 2 O 3 (0001) surface. The following section will provide basic information of the atomic and electronic structure aforementioned surfaces.…”

“…While these adsorption sites exist for ideal f cc (111) surfaces, it should be noted that surface atoms tend to minimize the surface energy by rearranging their surface position leading to a reconstructed surface which usually includes a less ordered structure. However, a reconstruction of clean f cc(111) metal surfaces does not occur at room temperature.…”

“…However, the graphene films are often not rotationally aligned to the metal surface, but display often a moiré structure with large periodicity, which results from the lattice mismatch between graphene and the underlying metal. Graphene on a Ni (111) surface represents an exception as it shows smallest lattice mismatch. The lattice mismatch between graphene and the nickel atom surface bond distance is about 111) surface.…”