The two-dimensional cobalt oxide (9 × 2) phase on Pd(100)

Gragnaniello, Luca; Barcaro, Giovanni; Sementa, Luca; Allegretti, Francesco; Parteder, G.; Surnev, S.; Steurer, Wolfram; Fortunelli, Alessandro; Netzer, H.

doi:10.1063/1.3578187

Cited by 24 publications

(46 citation statements)

References 40 publications

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“…These findings are in contrast to a recent study for the closely related system of a CoO bilayer on Pd(100) with (9 × 2) periodicity, for which only a moderately corrugated structure (height modulations of 0.18Å and 0.12Å for the oxygen and cobalt, respectively) was reported. 20 Similarly small corrugations were also reported for the FeO bilayer on Pt(111). 14 The aim of the present study is to test the extent to which the parameters of the DFT calculation and the magnetic order of the film influence the correspondence between the calculated and the experimentally determined structure.…”

Section: Introductionmentioning

confidence: 63%

“…We performed DFT calculations using the standard PBE functional with two distinct starting configurations: in one case we started with a slightly distorted, but otherwise flat, CoO bilayer that should easily converge into the structure found on Pd(100). 20 In the other case, we modified the above structure to contain two different types of oxygen species (low-lying and high-lying ones mimicking the LEED results 19 ) as indicated by the different shading in Fig. 1.…”

Section: Resultsmentioning

confidence: 99%

“…Candidates are rock-salt type FeO, MnO, and CoO films of (111) orientation, for which films of ultimate thinness -single hexagonal metal-oxygen bilayers -have been found on a number of metal substrates. [11][12][13][14][15][16][17][18][19][20] In these cases high-order commensurate phases were reported with unit cell dimensions of about ten times that of the substrate, corresponding to about 10% lattice misfits between substrates and oxide films. In the case of (100) oriented substrates, this just leads to close correspondence of row distances in one direction and, by a slight uniaxial distortion, the films achieve one-dimensional commensurability (row-on-row matching).…”

Section: Introductionmentioning

confidence: 99%

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Incommensurate Moiré overlayer with strong local binding: CoO(111) bilayer on Ir(100)

et al. 2012

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Incommensurate relaxed overlayer Moiré structures are often interpreted as systems with weak lateral variations of the binding potential and thus no structural modulations in the overlayer material. We discuss here the example of a CoO(111) bilayer on Ir(100), which is a relaxed overlayer with strong structural response to the lateral modulation of interface properties but nevertheless is incommensurate. By means of DFT calculations we quantitatively reproduce all the structural parameters of the CoO(111) bilayer on Ir(100) as proposed by a recent LEED analysis [C. Ebensperger et al., Phys. Rev. B 81, 235405 (2010)]. The calculations predict energetic degeneracies with respect to registry shifts of the CoO(111) film along [011]. Large-scale, low-temperature STM topographies reveal that the true structure of the film is incommensurate in this direction, exhibiting a onedimensional Moiré pattern with a period of about 9.4 aIr. From DFT calculations for limiting (periodic) models, we can sample the potential landscape of the cobalt and oxygen atoms in the Moiré structure across the Ir(100) unit cell. We find that despite the non-commensurability of the film, the binding to the substrate is site specific with strong attraction and repulsion points for both cobalt and oxygen atoms, leading to severe local distortions in the film. The lateral modulation of the structural elements within the oxide film can be understood as a combination of the lateral variation in the Co-Ir binding potential and additional O-Ir binding.

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Section: Introductionmentioning

confidence: 63%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Incommensurate Moiré overlayer with strong local binding: CoO(111) bilayer on Ir(100)

et al. 2012

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“…We recall that a c(4 × 2) superstructure like the one observed here has been reported for a number of rocksalt-type oxides on Pd(001). 19,61,62 In those cases, the occurrence of metal vacancies has been proposed as a mechanism able to compensate the compressive stress due to a large lattice mismatch between the substrate and the overlayer. In the present case, however, the interfacial strain is unlikely to be relevant in inducing cation vacancies.…”

Section: Discussionmentioning

confidence: 99%

“…11 The interest in one-layer-thick oxides is manifold, in particular (i) two-dimensional oxides can be seen as model systems for the oxide/metal interface, allowing investigation by means of high-resolution scanning probe techniques; (ii) the vertical confinement and the elastic and electronic coupling with the metallic substrate allows stabilizing stoichiometries and atomic structures that can differ with respect to the corresponding bulk terminations, with important implications in chemical reactivity, 12,13 adsorption properties, 14 and magnetic ordering 15 of the resulting structures; and (iii) the wetting layer can represent the precursor phase for the growth of thicker films. 16,17 Single layers of transition metal oxides have been stabilized on noble and quasinoble metals such as, for instance, Pd, 18,19 Ag, 20,21 Pt, 22,23 Au, 24 and Ir. 25 In these cases, growth techniques such as reactive deposition (i.e., metal deposition in oxygen atmosphere) and/or postoxidation are typically applied, leading to ordered phases and well-defined oxidemetal interfaces.…”

Section: Introductionmentioning

confidence: 99%

Self-organized chromium oxide monolayers on Fe(001)

et al. 2013

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The oxygen-saturated Fe(001)-p(1 × 1)O surface has been used as a template to stabilize two-dimensional Cr oxides on Fe(001). Cr deposition at 400 • C leads to two different well-ordered phases, depending on the amount of Cr deposited. In the submonolayer regime a novel c(4 × 2) overlayer self-assembles on the Fe(001)-p(1 × 1)O surface, saturating for a coverage of about 0.75 monolayers. This phase becomes unstable for higher coverages, when a ( √ 5 × √ 5)R27 • superstructure emerges. The structural and electronic details of the two one-layer-thick oxides are studied by combining high-resolution scanning tunneling microscopy, low-energy electron diffraction, Auger electron spectroscopy, and density functional theory.

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Atomically Thin 2D Transition Metal Oxides: Structural Reconstruction, Interaction with Substrates, and Potential Applications

Yang

Song

Callsen

et al. 2018

Adv Materials Inter

117

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Most of the large variety of 2D materials are derived from their parent van der Waals (vdWs) crystals, thus their atomic struc tures are identical to the bulk counterparts with some minor lattice constant differ ence due to the reduced dimensionality and vanished interlayer interaction. Simi larly, some 2D monolayers, of which a typical example would be silicene, [10] stem from bulk materials with covalent bonds. Although their bonding may significantly change (silicene: sp 2 ; bulk silicon: sp 3 ) when they go from the bulk material to the 2D monolayer, their atomic structures are analogous. However, a slight atomic relaxation may occur in order to balance the reduced bonding coordination in the 2D forms. Therefore, in these cases, the determination of the 2D atomic structures is quite straightforward.In contrast, most metal oxides feature strong interlayer ionic bonds. The lack of a strong interlayer interaction in their 2D forms usually introduces dangling bonds, leading to strong surface polarization which induces surface instability of 2D metal oxides. Pronounced lattice relaxation, prominent struc tural reconstruction and substrate effects have been identified as the main mechanisms for compensating such strong sur face polarization in 2D metal oxides, as have been observed for a Pd 5 O 4 overlayer on Pd(111), [22] a strained PdO(101) layer on Pd (100), [23] a Ag 1.83 O trilayer on Ag(111), [24] a RhO 2 trilayer on Rh(111), [25] multiple phases of 2D Mn oxides on Pd(100), [26] and TiO 2 on rutile TiO 2 (011). [27] All of these significant changes increase the difficulty of synthesizing 2D metal oxides, as well as pose a challenge to computational structure prediction methods. Notwithstanding, more recently, spectacular progress has been made in prediction, design, preparation, and charac terization of oxide monolayers owing to the advancement of growth technologies and novel synthesis routes, as well as the development of computational and theoretical methods. [28][29][30][31][32][33] The structural reconstructions in combination with the elec tron confinement in 2D and the large surfacetovolume ratio endow 2D transition metal oxides (TMOs) with stunning physical/chemical properties. Moreover, the 2D TMOs showThe discovery of graphene has stimulated dramatic research interest on other 2D materials including transition metal oxide (TMO) monolayers in order to realize novel functionalization and applications. Due to reduced bonding coordination and strong surface polarization, the structures of most TMOs in the monolayer limit are very different from their bulk counterparts, as well as their physical and chemical properties. In this brief review, the authors sum marize recent research progress on atomically thin TMO layers. The focus is on the structural properties of the TMOs and their interaction with the sub strates from the computational point of view. The authors also introduce the potential applications of the TMO 2D materials on supercapacitors, photo catalysts, batteries, and sensors.

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The two-dimensional cobalt oxide (9 × 2) phase on Pd(100)

Cited by 24 publications

References 40 publications

Incommensurate Moiré overlayer with strong local binding: CoO(111) bilayer on Ir(100)

Incommensurate Moiré overlayer with strong local binding: CoO(111) bilayer on Ir(100)

Self-organized chromium oxide monolayers on Fe(001)

Atomically Thin 2D Transition Metal Oxides: Structural Reconstruction, Interaction with Substrates, and Potential Applications

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