Adsorption of atomic and molecular oxygen on Cu(100)

Puisto, Antti; Pitkänen, H.; Alatalo, M.; Jaatinen, Sampsa; Salo, Petri; Foster, Adam S.; Kangas, Teija; Laasonen, Kari

doi:10.1016/j.cattod.2004.09.072

Cited by 30 publications

(20 citation statements)

References 19 publications

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“…Thermodynamically, subsurface embedment is also strongly affected by oxygen coverage of the top surface as shown in previous DFT calculations, e.g., subsurface embedded oxygen is energetically unfavorable by 0.08 eV on clean Cu(100) surface but favored by 1.40 eV if an oxygen adatom pre-exists on the surface. 43 Additionally, from the MD simulations we observe that the surfaces become less susceptible to oxidation beyond the 1 ML limit due to the smaller oxygen adsorption probability on the surface compared to the low-coverage limit and the increase in the oxygen desorption probabilities. All of these factors combined together result in the reduced rate of subsurface oxidation.…”

Section: ■ Computational Detailsmentioning

confidence: 95%

Step-Induced Oxygen Upward Diffusion on Stepped Cu(100) Surface

2014

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Surface defects such as step edges play an important role in determining the surface properties, affecting immensely the growth mechanisms and morphologies of the nanostructures in epitaxial film growth processes. Here, we probe the dynamics of the oxidation on stepped Cu(100) using molecular dynamic simulations in conjunction with a reactive force field, and we elucidate the mechanisms and energy barriers affecting the oxidation process. Molecular dynamic simulations show that the adsorbed oxygen adatoms are unevenly distributed on the stepped surface, favoring the top terrace. We show that this behavior is due to Ehrlich− Schwobel (ES) barrier effect. However, differently from the reduced interlayer self-diffusion in descending a step as in a conventional ES barrier effect, we find instead that the ES barrier reduces the ascending diffusion barrier for oxygen, promoting its transport across the step edge and enhancing oxidation of the upper terrace. Additionally, we find that the ES barrier is stepheight dependent, where higher step edges reduce more the oxygen-ascending diffusion barrier and favor more oxidation of the upper terraces of stepped surfaces. ■ INTRODUCTIONSelf-assembly of nanostructures on thin films is of interest to several fields including catalysis, electronics, and information technology. 1−3 For many experimental conditions it is often that nanostructure growth is far from equilibrium where kinetic effects are of key importance in determining the growth morphology. 4 Depending on the nature of the supporting base and the deposited materials as well as the growth environment, nanostructures with different morphologies can self-assemble during homoepitaxial or heteroepitaxial film growth processes. Additionally, the existence of defects and, in particular, step edges on the substrate can have a profound effect on the self-assembly. For example, on copper, which is one of the best catalysts in heterogeneous catalysts, a recent in situ high-resolution transmission electron microscopy study showed that oxidation of stepped Cu(100) surfaces promotes formation of a flat metal− oxide interface through the Cu adatoms detachment from steps and diffusion across the terraces. 5 For stepped surfaces, one key question is whether the surface growth process promotes formation of a smooth two-dimensional (2D) film or a three-dimensional (3D) island structure. 6−9 In this respect, the Ehrlich−Schwobel (ES) barrier at the interlayer interface 10,11 has been shown to play an important role in determining the off-balance between these two growth mechanisms. The basic concept of the ES barrier is due to bond counting where an adatom approaching the ledge of a step sees less neighbors compared to the terrace, which in turn demotes the descending movement off a step edge. The ES barrier has been shown to reduce the interlayer mass exchange and promotes formation of 3D island structure in homoepitaxial and heteroepitaxial film growth. 6−8 There are several factors affecting the magnitude of the ES barrier, such as...

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Section: ■ Computational Detailsmentioning

confidence: 95%

Step-Induced Oxygen Upward Diffusion on Stepped Cu(100) Surface

2014

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“…At low temperatures (up to 100 K) and low coverage (∼ 0.1 monolayers, ML, defined as one adsorbed oxygen atom for every surface copper atom) experimental and computational evidence has shown that incident oxygen molecules dissociate with the oxygen atoms adsorbing at the hollow site [123][124][125][126][127][128] . These dissociated oxygen atoms stabilize chemisorption of further incoming oxygen molecules at higher coverages [129][130][131][132] .…”

Section: Cu(100)mentioning

confidence: 99%

Atomistic details of oxide surfaces and surface oxidation: the example of copper and its oxides

Gattinoni

Michaelides

2015

Surface Science Reports

270

258

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The oxidation and corrosion of metals are fundamental problems in materials science and technology that have been studied using a large variety of experimental and computational techniques. Here we review some of the recent studies that have led to significant advances in our atomic-level understanding of copper oxide, one of the most studied and better understood metal oxides. We show that a good atomistic understanding of the physical characteristics of cuprous (Cu 2 O) and cupric (CuO) oxide and of some key processes of their formation has been obtained. Indeed, the growth of the oxide has been proven to be epitaxial with the surface and to proceed, in most cases, through the formation of oxide nano-islands which, with continuous oxygen exposure, grow and eventually coalesce. We also show how electronic structure calculations have become increasingly useful in helping to characterise the structures and energetics of various Cu oxide surfaces. However a number of challenges remain. For example, it is not clear under which conditions the oxidation of copper in air at room temperature (known as native oxidation) leads to the formation of a cuprous oxide film only, or also of a cupric overlayer. Moreover, the atomistic details of the nucleation of the oxide islands are still unknown. We close our review with a perspective on future work and discuss how recent advances in experimental techniques, bringing greater temporal and spatial resolution, along with improvements in the accuracy, realism and timescales achievable with computational approaches make it possible for these questions to be answered in the near future.

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“…A more reactive surface such as a copper one would lead to stronger hybridization with the molecule and to a larger charge transfer, pulling the g resonance completely below the Fermi energy. 40 For a copper surface, the mixed-valence regime described above is not possible. …”

Section: Electronic Structure Of O 2 On Ag(110)mentioning

confidence: 99%

Role of molecular electronic structure in inelastic electron tunneling spectroscopy:O2on Ag(110)

2010

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Density-functional theory ͑DFT͒ simulations corrected by the intramolecular Coulomb repulsion U are performed to evaluate the vibrational inelastic electron tunneling spectroscopy ͑IETS͒ of O 2 on Ag͑110͒. In contrast to DFT calculations that predict a spinless adsorbed molecule, the inclusion of the U correction leads to the polarization of the molecule by shifting a spin-polarized molecular orbital toward the Fermi level. Hence, DFT+ U characterizes O 2 on Ag͑110͒ as a mixed-valent system. This has an important implication in IETS because a molecular resonance at the Fermi level can imply a decrease in conductance while in the off-resonance case, an increase in conductance is the expected IETS signal. We use the lowest-order expansion on the electron-vibration coupling in order to evaluate the magnitude and spatial distribution of the inelastic signal. The final IET spectra are evaluated with the help of the self-consistent Born approximation and the effect of temperature and modulation-voltage broadening are explored. Our simulations reproduce the experimental data of O 2 on Ag͑110͒ ͓J. R. Hahn, H. J. Lee, and W. Ho, Phys. Rev. Lett. 85, 1914 ͑2000͔͒ and give extra insight of the electronic and vibrational symmetries at play. This ensemble of results reveals that the IETS of O 2 is more complicated that a simple decrease in conductance and cannot be ascribed to the effect of a single molecular-orbital resonance.

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Adsorption of atomic and molecular oxygen on Cu(100)

Cited by 30 publications

References 19 publications

Step-Induced Oxygen Upward Diffusion on Stepped Cu(100) Surface

Step-Induced Oxygen Upward Diffusion on Stepped Cu(100) Surface

Atomistic details of oxide surfaces and surface oxidation: the example of copper and its oxides

Role of molecular electronic structure in inelastic electron tunneling spectroscopy:O2on Ag(110)

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