Growth and Morphology of Calcium-Oxide Films Grown on Mo(001)

Shao, Xiang; Myrach, Philipp; Nilius, Niklas; Freund, Hans‐Joachim

doi:10.1021/jp201852x

Cited by 49 publications

(64 citation statements)

References 32 publications

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“…The CaO films were prepared by Ca deposition onto a Mo(001) single crystal in 5 × 10 −7 mbar of O 2 , followed by vacuum annealing to stimulate film crystallization [12]. Most of the samples were actually fabricated with a two-step procedure.…”

Section: Methodsmentioning

confidence: 99%

Evolution of the electronic structure of CaO thin films following Mo interdiffusion at high temperature

et al. 2015

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The electronic structure of CaO films of 10-60 monolayer thickness grown on Mo(001) has been investigated with synchrotron-mediated x-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM). Upon annealing or reducing the thickness of the film, a rigid shift of the CaO bands to lower energy is revealed. This evolution is explained with a temperature-induced diffusion of Mo ions from the metal substrate to the oxide and their accumulation in the interface region of the film. The Mo substitutes divalent Ca species in the rocksalt lattice and is able to release electrons to the system. The subsequent changes in the Mo oxidation state have been followed with high-resolution XPS measurements. While near-interface Mo transfers extra electrons back to the substrate, generating an interface dipole that gives rise to the observed band shift, near-surface species are able to exchange electrons with adsorbates bound to the oxide surface. For example, exposure of O 2 results in the formation of superoxo species on the oxide surface, as revealed from STM measurements. Mo interdiffusion is therefore responsible for the pronounced donor character of the initially inert oxide, and largely modifies its adsorption and reactivity behavior.

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Section: Methodsmentioning

confidence: 99%

Evolution of the electronic structure of CaO thin films following Mo interdiffusion at high temperature

et al. 2015

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“…The films are characterized by a square (1 1) LEED pattern, indicative of the (001) termination of the CaO surface, and by flat terraces of approximately 100 nm 2 in size in STM. [19] The CaO films are subject to self-doping, proceeding by spontaneous diffusion of Mo ions from the metal support into the film at elevated temperature. [20] While interfacial oxide planes contain up to 25 % Mo ions, this number decreases with increasing film thickness.…”

Section: Dedicated To Professor Helmut Schwarz On the Occasion Of Hismentioning

confidence: 99%

Adsorption, Activation, and Dissociation of Oxygen on Doped Oxides

et al. 2013

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Charge transfer in the presence of dopants is relevant for the adorption and activation of small molecules, such as O2 . Scanning tunneling microscopy and DFT calculations provide evidence for the formation of strongly bound superoxo species on chemically inert, Mo-doped CaO films. This oxygen surface species shows a high propensity to dissociate. Dopants could also be important for the activation of hydrocarbons on inert oxides.

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“…8,11 Preparation of high quality crystalline calcium-oxide (CaO) films is more difficult as compared to that of MgO. The CaO thin-films have been grown on a Mo(001) support, 12 and exhibited similar electronic and optical properties of bulk CaO.…”

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Monolayer alkali and transition-metal monoxides: MgO, CaO, MnO, and NiO

et al. 2017

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Two dimensional crystals with strong interactions between layers has attracted increasing attention in recent years in a variety of fields. In particular, the growth of single layer of oxide materials (e.g. MgO, CaO, NiO and MnO), over metallic substrates were found to display different physical properties than their bulk. In this study, we report on physical properties of single layer of metallic oxide materials and compare their properties with their bulk and other two dimensional (2D) crystals. We found that the planar structure of metallic monoxides are unstable instead the buckled structure are thermodynamically stable. Also, the 2D-MnO and NiO exhibit different magnetic (ferromagnetic) and optical properties than their bulk whereas band gap energy and linear stiffness found to be decreasing from NiO to MgO. Our findings provide novel insight into oxide thin-film technology applications.

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Growth and Morphology of Calcium-Oxide Films Grown on Mo(001)

Cited by 49 publications

References 32 publications

Evolution of the electronic structure of CaO thin films following Mo interdiffusion at high temperature

Evolution of the electronic structure of CaO thin films following Mo interdiffusion at high temperature

Adsorption, Activation, and Dissociation of Oxygen on Doped Oxides

Monolayer alkali and transition-metal monoxides: MgO, CaO, MnO, and NiO

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