Photoemission study of the electronic structure of Mo and Mo oxides

Werfel, F.; Minni, E.

doi:10.1088/0022-3719/16/31/022

Cited by 213 publications

(152 citation statements)

References 18 publications

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“…Simultaneously, a high-energy doublet, denoted with (c), shows up at 233.4 eV and develops the largest intensity of all Mo features upon annealing. It has been matched to fully oxidized Mo 6+ , although its BE is somewhat higher than the literature value of 232.7 eV [20]. The difference would be in line with the band-bending effect that has been identified previously for the Ca and O BE values (Fig.…”

Section: B Evolution Of the Mo Core-level Spectra During Cao Annealingsupporting

confidence: 87%

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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: B Evolution Of the Mo Core-level Spectra During Cao Annealingsupporting

confidence: 87%

“…2(a)]. We note that the temperature effect is most pronounced for an intermediate film thickness (20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30) and fades away for thicker films. Conversely, the band onset can be tuned by varying the film thickness and keeping the annealing temperature constant at 1000 K. This trend is 035418- 2 FIG.…”

Section: (E)mentioning

confidence: 83%

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

et al. 2015

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“…1(a) is confirmed by the evolution of the XPS valence band energy distribution curves of Mo depicted in Fig. 2(a), and characterized by a broad overall band with a maximum intensity at 2 eV below the Fermi level 49 E F . The broad emission centered at ∼ 6 eV is assigned to an O2p photoemission signal of adsorbed oxygen, with contributions from various oxygen species.…”

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confidence: 53%

Processing and charge state engineering of MoOx

et al. 2017

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The effects of wet chemical processing employed in device fabrication standards are studied on molybdenum oxide (MoOx) ultra-thin films. We have combined x-ray photoelectron spectroscopy (XPS), angle resolved XPS and x-ray reflectivity to gain insight into the changes in composition, structure and electronic states upon treatment of films with different initial stoichiometry prepared by reactive sputtering. Our results show significant reduction effects associated with the development of gap states in MoOx, as well as changes in the composition and structure of the films, systematically correlated with the initial oxidation state of Mo.

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“…Oxygen vacancies both donate electrons to the Mo 4d states and reduce the crystal field sufficiently to allow the formation of extended 4d gap states. 17 Photovoltaics is a rapidly growing technological field and one in which MoO 3 has found several niches, being used as an electron injection layer in organic solar cells and gaining interest as an absorbing material in new generations of solar cells. 9,[18][19][20][21][22] Due to the importance of energy level alignment, interband transitions and optical properties in photovoltaic applications, awareness of the effect of oxygen non-stoichiometry on the electronic structure of MoO 3 is 5 imperative for design of high-efficiency devices.…”

Section: Figurementioning

confidence: 99%

A van der Waals Density Functional Study of MoO₃ and Its Oxygen Vacancies

et al. 2016

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The electronic structure of layered molybdenum trioxide MoO 3 is highly sensitive to changes in oxygen stoichiometry as Mo 6+ has an empty 4d shell. Applications of MoO 3 are responsive to small changes in vacancy concentration, with some functions relying on a narrow window of oxygen non-stoichiometry. Difficulties in analyzing the energetics of oxygen vacancies by computational methods stem from the inability to accurately model the layered structure of MoO 3 . One unit cell parameter is governed by long range forces across the structural gaps and these dispersed interactions are not well described by conventional density functional theory (DFT) methods. With the exchange functional vdW-DF2 we accurately model the structure, in good agreement with experimental data. This basis allows exploration of the effect of oxygen non-stoichiometry on the electronic structure and properties of the oxygen deficient material.The layered structure efficiently screens the structural perturbations caused by oxygen vacancies.The enthalpies of formation are calculated for oxygen vacancies at the three symmetry inequivalent oxygen sites. The oxygen deficiency in MoO 3 gives rise to Mo 4d gap states with energy levels dependent on the type of oxygen vacancy.

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Photoemission study of the electronic structure of Mo and Mo oxides

Cited by 213 publications

References 18 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

Processing and charge state engineering of MoOx

A van der Waals Density Functional Study of MoO₃ and Its Oxygen Vacancies

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Photoemission study of the electronic structure of Mo and Mo oxides

Cited by 213 publications

References 18 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

Processing and charge state engineering of MoOx

A van der Waals Density Functional Study of MoO3 and Its Oxygen Vacancies

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A van der Waals Density Functional Study of MoO₃ and Its Oxygen Vacancies