Charge and Ion Transport in NiO and Aspects of Ni Oxidation from First Principles

Yu, Jianguo; Rosso, Kevin M.; Bruemmer, S.M.

doi:10.1021/jp208080v

Cited by 64 publications

(54 citation statements)

References 39 publications

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“…Recently, nickel vacancies (V Ni ") were proven to play an important role in NiO films' electrical properties. These can be spontaneously formed under oxygen-rich conditions [27,28]. Holes can be generated from nickel vacancies and are responsible for the films' p-type conductivity.…”

Section: Introductionmentioning

confidence: 99%

The Influence of Oxygen Flow Ratio on the Optoelectronic Properties of p-Type Ni1−xO Films Deposited by Ion Beam Assisted Sputtering

et al. 2018

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In this work, p-type non-stoichiometric Ni 1−x O thin films were deposited by oxygen ion beam assisted RF sputtering on glass substrates. The influence of the oxygen flow ratio (0-100%) on the films' optoelectronic properties was investigated. In our experimental conditions, all the films are crystallized in the cubic NiO phase. However, their crystallinity and mean grain size decreases with increasing oxygen flow ratios. Meanwhile, the films' conductivity improves from 9.1 to 25.4 S•cm −1. This is due to the fact that the nickel vacancies along with hole carriers can be introduced into NiO films when they are deposited under higher oxygen flow ratio conditions. Thus, the O-rich environment is beneficial in enhancing the films' carrier concentrations. In addition, with an increasing oxygen flow ratio, the film's transmittance degrades. The direct optical band gap of Ni 1−x O films declines slightly from 3.99 to 3.95 eV, with the oxygen flow ratio increasing from 0% to 100%.

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Section: Introductionmentioning

confidence: 99%

The Influence of Oxygen Flow Ratio on the Optoelectronic Properties of p-Type Ni1−xO Films Deposited by Ion Beam Assisted Sputtering

et al. 2018

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“…it contracts (Table 1). Such behaviour is not possible in the perfect cubic lattice, however in real nanoparticles/nanocrystallites the effect is caused by the Ni-O bond shortening at the surface and around nickel vacancies [19,35,36], which are present in our dark brown thin films [9][10][11]. In the next section we will demonstrate how the average size of nanoparticles/nanocrystallites and the concentration of nickel vacancies can be simultaneously estimated by taking into account multiple-scattering effects in the EXAFS analysis.…”

Section: Extended X-ray Absorption Fine Structure (Exafs)mentioning

confidence: 93%

“…The film deposition was performed at three Ar/O 2 ratios equal to 0/100 (TF1), 50/50 (TF2) and 90/10 (TF3). Thus obtained thin films had thicknesses of about 1 m and dark brown colour, suggesting the presence of nickel vacancies [9][10][11]. Commercial microcrystalline NiO powder (c-NiO, Aldrich, 99%), having green colour, was used for comparison.…”

Section: Methodsmentioning

confidence: 99%

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Local structure relaxation in nanocrystalline Ni1−xO thin films

et al. 2014

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Non-stoichiometric nickel oxide (Ni 1-x O) thin films were prepared by DC magnetron sputtering technique in mixed Ar/O 2 atmosphere and studied by synchrotron radiation Ni K-edge x-ray absorption spectroscopy, x-ray diffraction and scanning electron microscopy. The use of advanced modelling technique, combining classical molecular dynamics with ab initio multiplescattering extended X-ray absorption fine structure (EXAFS) calculations, allowed us to describe the structure relaxation and dynamics in nanocrystallites and to estimate their size and the concentration of nickel vacancies. Highlights Nickel oxide thin films were prepared by DC magnetron sputtering. Local structure of Ni 1-x O thin films was studied by x-ray absorption spectroscopy. The atomic structure of Ni 1-x O thin films is strongly relaxed. Ni vacancies in Ni 1-x O thin films play important role in atomic structure relaxation.

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“…However, due to limitations on the length scales accessible to quantum mechanical simulations, this information is limited to treatment of microscopic processes in isolation, such as transport, 10,11 defect formation, and migration energetics at metal/oxide interface 12 and interfacial potential build up. 13 To access the dynamics of the oxidation processes on the atomistic level, ab initio molecular dynamics (MD) was employed to study very early stages of grain boundary oxidation of binary alloys. 14 Elementary quantum mechanical information has also been linked with more computationally efficient classical models to model high temperature segregation of minor elements at the surface of metal alloy.…”

Section: Introductionmentioning

confidence: 99%

Multiscale model of metal alloy oxidation at grain boundaries

Sushko

Alexandrov

Schreiber

et al. 2015

The Journal of Chemical Physics

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High temperature intergranular oxidation and corrosion of metal alloys is one of the primary causes of materials degradation in nuclear systems. In order to gain insights into grain boundary oxidation processes, a mesoscale metal alloy oxidation model is established by combining quantum Density Functional Theory (DFT) and mesoscopic Poisson-Nernst-Planck/classical DFT with predictions focused on Ni alloyed with either Cr or Al. Analysis of species and fluxes at steady-state conditions indicates that the oxidation process involves vacancy-mediated transport of Ni and the minor alloying element to the oxidation front and the formation of stable metal oxides. The simulations further demonstrate that the mechanism of oxidation for Ni-5Cr and Ni-4Al is qualitatively different. Intergranular oxidation of Ni-5Cr involves the selective oxidation of the minor element and not matrix Ni, due to slower diffusion of Ni relative to Cr in the alloy and due to the significantly smaller energy gain upon the formation of nickel oxide compared to that of Cr2O3. This essentially one-component oxidation process results in continuous oxide formation and a monotonic Cr vacancy distribution ahead of the oxidation front, peaking at alloy/oxide interface. In contrast, Ni and Al are both oxidized in Ni-4Al forming a mixed spinel NiAl2O4. Different diffusivities of Ni and Al give rise to a complex elemental distribution in the vicinity of the oxidation front. Slower diffusing Ni accumulates in the oxide and metal within 3 nm of the interface, while Al penetrates deeper into the oxide phase. Ni and Al are both depleted from the region 3-10 nm ahead of the oxidation front creating voids. The oxide microstructure is also different. Cr2O3 has a plate-like structure with 1.2-1.7 nm wide pores running along the grain boundary, while NiAl2O4 has 1.5 nm wide pores in the direction parallel to the grain boundary and 0.6 nm pores in the perpendicular direction providing an additional pathway for oxygen diffusion through the oxide. The proposed theoretical methodology provides a framework for modeling metal alloy oxidation processes from first principles and on the experimentally relevant length scales.

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Charge and Ion Transport in NiO and Aspects of Ni Oxidation from First Principles

Cited by 64 publications

References 39 publications

The Influence of Oxygen Flow Ratio on the Optoelectronic Properties of p-Type Ni1−xO Films Deposited by Ion Beam Assisted Sputtering

The Influence of Oxygen Flow Ratio on the Optoelectronic Properties of p-Type Ni1−xO Films Deposited by Ion Beam Assisted Sputtering

Local structure relaxation in nanocrystalline Ni1−xO thin films

Multiscale model of metal alloy oxidation at grain boundaries

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