Elucidating the Structure and Chemical State of Co Growth on the ZnO(101̅0) Surface

Abstract

This study elucidates the epitaxial growth structure and chemical state of Co on the ZnO(101̅0) surface by using scanning tunneling microscopy, reflection high-energy electron diffraction, X-ray photoelectron spectroscopy, and ultraviolet photoelectron spectroscopy. The well-ordered cobalt oxide (CoO x )(2 × 1) structure is formed at 0.5 ML Co coverage. Increasing the Co coverage from 0.7 to 1 ML allows for the surface characterization by the Co stripe structure, while the Co metallic clusters are clearly developed above 3 ML Co coverage. Coverage-dependent measurements of the Co chemical state indicate that the initial Co mixed oxidation and metallic state exists at submonolayer and gradually transfers to a metallic Co-dominated state. The results also suggest that the initial growth mode is two-dimensional-like and bridged to three-dimensional at higher Co coverages.

Graphene‐Coated ZnO and SiO2 as Supports for CoO Nanoparticles with Enhanced Reducibility

“…The AFM topography images on bare SiO 2 and ZnO substrates show the formation of a uniform Co layer that follows the local high and low features of the substrate . This indicates that cobalt deposition on oxide substrates either approximates a layer‐by‐layer growth mode or forms a high density of small 3D clusters that coalesce into a continuous film . On the contrary, on carbon substrates [graphene‐covered oxides and highly oriented pyrolytic graphite (HOPG)], cobalt forms individual, homogenously sized nanoparticles, which increase the surface roughness, as demonstrated by the vertical profile along the cross‐sectional lines shown in Figure S2.…”

Magnetism modulation of Fe/ZnO heterostructure by interface oxidation

“…Su et al reported the thickness-dependent transition of Co chemical state from the initial Co mixed oxidation to metallic state in Co/ZnO(10 10). 7 Results of Wett et al show that, at ambient temperature, Fe grows on ZnO(0001) in the pseudo layer-by-layer mode with the FeO formation at the interface. 8 Annealing leads to a stepwise oxidation of the Fe to FeO (670 K) and Fe 2 O 3 (820 K).…”

Recent Advances in Palladium‐Catalyzed Cycloadditions Involving Trimethylenemethane and its Analogs

“…This dynamic behavior, which can be envisioned as having the palladium center whirl around the ligand, is also manifested in substituted systems. Again, this observation is explained by a faster equilibration (compared with cycloaddition) between the two initially formed TMM complexes (7) and (8), and that (7) is more reactive towards addition to the olefin (Scheme 2.2). Again, this observation is explained by a faster equilibration (compared with cycloaddition) between the two initially formed TMM complexes (7) and (8), and that (7) is more reactive towards addition to the olefin (Scheme 2.2).…”

“…Cycloadditions of either of the methyl precursor (5) or (6) give the same major product (9) (80-100% depending on the nature of the olefin). Interestingly, the theoretical study by Fenske suggests that complex (7) is also favored thermodynamically [8]. Interestingly, the theoretical study by Fenske suggests that complex (7) is also favored thermodynamically [8].…”

“…The advancements include the development of substituted analogs, improved catalytic systems, other TMM precursors, and analogous cycloaddition reactions involving both inter-and intramolecular systems. An X-ray crystallographic analysis of a stable TMM-Pd complex prepared by a different route indicates that the ligand binds in an unsymmetrical g 3 mode, in contrast to virtually all other metal complexes of this fragment which have symmetrical g 4 binding mode [7]. This chapter will focus only on the TMM chemistry using Trost's approach, even though other methodologies are also available [3,4].…”