Quantitative Multilayer Cu(410) Structure and Relaxation Determined by QLEED

Abstract

Industrially relevant catalytically active surfaces exhibit defects. These defects serve as active sites; expose incoming adsorbates to both high and low coordinated surface atoms; determine morphology, reactivity, energetics, and surface relaxation. These, in turn, affect crystal growth, oxidation, catalysis, and corrosion. Systematic experimental analyses of such surface defects pose challenges, esp., when they do not exhibit order. High Miller index surfaces can provide access to these features and information, albeit indirectly. Here, we show that with quantitative low-energy electron diffraction (QLEED) intensity analyses and density functional theory (DFT) calculations, we can visualize the local atomic configuration, the corresponding electron distribution, and local reactivity. The QLEED-determined Cu(410) structure (Pendry reliability factor RP ≃ 0.0797) exhibits alternating sequences of expansion (+) and contraction (−) (of the first 16 atomic interlayers) relative to the bulk-truncated interlayer spacing of ca. 0.437 Å. The corresponding electron distribution shows smoothening relative to the bulk-determined structure. These results should aid us to further gain an atomic-scale understanding of the nature of defects in materials.

Directional growth of iron oxide nanowires on a vicinal copper surface

“…As the angle between the spots is 60 • , it may be assumed that they originate from a hexagonal structure-most probably iron oxide growing in the [111] direction. This growth orientation agrees well with the one determined based on the atomicallyresolved STM image (figure 3(b)), as well as the one reported for iron oxides on Cu(001) [34][35][36][37][38] (the 4-atom-wide terraces of Cu(410)-O have a Cu(001) structure [29]). At the vicinity of the central line running in the [010] direction, spots positioned ±15 • with respect to the centre of symmetry can be seen (marked with red arrows).…”

“…The selected substrate-Cu(410)-is a vicinal Cu(001) surface. A perfect bulk-cut Cu(410) is characterized by 4-atom-wide terraces exhibiting a slightly reconstructed Cu(001) structure and separated by monoatomic steps representing the (110) plane [29]. The width of each terrace is ∼7.2 Å and the step height is 1.75 Å [30,31].…”