Phonon-Mediated Electron Transport through CaO Thin Films

Cui, Yi; Tosoni, Sergio; Schneider, W. D.; Pacchioni, Gianfranco; Nilius, Niklas; Freund, Hans‐Joachim

doi:10.1103/physrevlett.114.016804

Cited by 19 publications

(30 citation statements)

References 40 publications

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“…We found that the 2D-CaO(100) have a direct band gap of 2.03 eV while bulk CaO, with cubic rocksalt structure, exhibits insulator behavior with a wide band gap of 7.7 eV. 42,43 This is consistent with experimentally observed decrease in the band gap of CaO thin-film 44,45 , i.e. Cui et.al have found the band gap of CaO thin-film grown on Mo(100) to be 7.1 eV using a low-temperature scanning tunneling microscopy technique.…”

Section: B Caosupporting

confidence: 85%

“…Cui et.al have found the band gap of CaO thin-film grown on Mo(100) to be 7.1 eV using a low-temperature scanning tunneling microscopy technique. 44 Notice here our finding (2.03 eV) is for a monolayer of CaO which is very thinner than those thin-film studied in refs. 44,45 .…”

Section: B Caocontrasting

confidence: 51%

“…44 Notice here our finding (2.03 eV) is for a monolayer of CaO which is very thinner than those thin-film studied in refs. 44,45 . Therefore, because of small indirect band gap one can conclude that monolayer of CaO(100) can show semiconducting properties.…”

Section: B Caocontrasting

confidence: 51%

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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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Section: B Caosupporting

confidence: 85%

Section: B Caocontrasting

confidence: 51%

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

et al. 2017

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“…Accordingly, atomic resolution could be achieved only in this thickness range. For thicker films (up to 50 ML) relevant for doping, electron hopping was identified as the dominant transport mechanism for electrons through the dielectric layer [6]. Our setup is equipped with an optical readout that enables the collection of photons from the tip-sample junction and their detection with a charge-coupled device unit outside the vacuum chamber.…”

Section: Methodsmentioning

confidence: 99%

Defect complexes in Li-doped MgO

et al. 2015

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Magnesium oxide (MgO) is used in a variety of industrial applications due to its low cost and structural stability. In heterogeneous catalysis, MgO and Li-doped MgO have been studied as catalysts for the oxidative coupling of methane. In this work, we analyze the structure and stability of defect complexes comprising Li dopants and oxygen vacancies in MgO, combining scanning tunneling microscopy, photon-emission experiments, and density-functional theory computations. The experimental results strongly indicate that after annealing Li-doped MgO to temperatures of 600 K and higher, Li evaporates from the surface, but Li defects, such as substitutional defects, interstitials, or defect complexes comprising Li remain in the bulk. Our calculations show that bulk defect complexes containing F 2+ color centers, that have donated their two electrons to two adjacent Li defects, are the most stable configurations at realistic pressure and temperature conditions.

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“…Recently, it has been proposed based on a low-temperature STM experiments that carrier transport in Mo supported CaO thin film is accompanied by strong phonon excitations [14]. Interestingly, phonon excitations showed various oscillating signals in the differential conductance (dI /dV ) depending on the thickness of CaO film.…”

Section: Introductionmentioning

confidence: 99%

Structure and dynamics of CaO films: A computational study of an effect of external static electric field

et al. 2017

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Häkkinen, H. (2017). Structure and dynamics of CaO films: A computational study of an effect of external static electric field. Physical Review B, 95 (16) Oxide films play a significant role in a wide range of industrial fields, mostly due to the thickness-dependent variation of their properties. Recently, it has been proposed based on the experimental study that carrier transport in CaO films proceeds via strong phonon excitations with a variable signal depending on the film thickness. In this paper, we report a detailed investigation in the frame of the density functional theory of structural and electronic properties of freestanding and Mo(100)-supported CaO films, as well as phonons therein, as functions of the film thickness and intensity of the external static electric field. Our calculations demonstrate that phonon frequencies negligibly depend on the external electric field. A small gradual increase of the energy of CaO phonons upon increase of the film thickness was found to be in line with earlier experimental findings. The effect of Mo support was observed in the systematic decrease of the energy of phonons. The applied electric field showed a minor effect on the structure of CaO films, whereas electronic properties of the oxide were significantly affected. In particular, the band gap of CaO films was found to gradually decrease with the growing intensity of the external electric field, while the effect is a more pronounced for thicker films. Overall, our paper provides innovative insights into the mechanism of electron transport and electronic properties of CaO films that might lead to new potential applications of oxide materials.

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Phonon-Mediated Electron Transport through CaO Thin Films

Cited by 19 publications

References 40 publications

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

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

Defect complexes in Li-doped MgO

Structure and dynamics of CaO films: A computational study of an effect of external static electric field

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