The effects of strain and vacancy defects on the electronic structure of Cr2O3

Mi, Zhishan; Chen, Li; Shi, Changmin; Ma, Yuan; Wang, Dongchao; Li, Xiaolong; Li, Hongmei; Li, Qiao

doi:10.1016/j.commatsci.2017.12.012

Cited by 26 publications

(13 citation statements)

References 38 publications

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“…A decrease in the optical gap was note when the NiO lattice parameter increased and the film turned into tensile strain [1 taking into account that the mean crystallite size decreases with tensile strain as observe here for the as-deposited NiO. Theoretical calculations indicated that tensile strain wou also reduce the gap of Cr2O3 [13]. Furthermore, Eg < 3.2 eV has been reported for Ni coatings with mean crystallite sizes below 20 nm [49] and Eg < 2.7 eV for Cr2O3 crystallit below 28 nm [50].…”

Section: Resultsmentioning

confidence: 69%

“…Due to its lower 3d occupation number, a lower U and higher electrical conductivity are expected for Cr 2 O 3 than NiO. Nevertheless, the respective electronic characteristics can be altered as previous studies have revealed that compressive strain can increase the band gap energy and U values in both Cr 2 O 3 [13] and NiO [14]. In addition, the metal vacancy defects play an important role in changing the lattice arrangement and introducing charge transition levels that modify the electronic bands [15,16].…”

Section: Introductionmentioning

confidence: 98%

“…Although with differences in their electronic structure, NiO (Ni 2+ 3d 8 ) and Cr 2 O 3 (Cr 3+ 3d 3 ) are equally suitable for acting as p-TCOs [6]. Both are transparent to the visible light due to optical absorption beginning at wavelengths below 0.4 µm and they allow the creation of holes by metal vacancy defects (V Ni or V Cr ) [12,13].…”

Section: Introductionmentioning

confidence: 99%

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Structural Changes Induced by Heating in Sputtered NiO and Cr2O3 Thin Films as p-Type Transparent Conductive Electrodes

Guillén

Herrero

2021

Electronic Materials

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NiO and Cr2O3 are transition metal oxides with a partially filled d electron band that supports p-type conduction. Both are transparent to the visible light due to optical absorption beginning at wavelengths below 0.4 μm and the creation of holes by metal vacancy defects. The defect and strain effects on the electronic characteristics of these materials need to be established. For this purpose, NiO and Cr2O3 thin films were deposited on unheated glass substrates by reactive DC sputtering from metallic targets. Their structural, morphological, optical and electrical properties were analyzed comparatively in the as-grown conditions (25 °C) and after heating in air at 300 °C or 500 °C. The cubic NiO structure was identified with some tensile strain in the as-grown conditions and compressive strain after heating. Otherwise, the chromium oxide layers were amorphous as grown at 25 °C and crystallized into hexagonal Cr2O3 at 300 °C or above also with compressive strain after heating. Both materials achieved the highest visible transmittance (72%) and analogous electrical conductivity (~10−4 S/cm) by annealing at 500 °C. The as-grown NiO films showed a higher conductivity (2.5 × 10−2 S/cm) but lower transmittance (34%), which were related to more defects causing tensile strain in these samples.

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Section: Resultsmentioning

confidence: 69%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

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Structural Changes Induced by Heating in Sputtered NiO and Cr2O3 Thin Films as p-Type Transparent Conductive Electrodes

Guillén

Herrero

2021

Electronic Materials

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“…Ni(111) presents a hexagonal symmetry with a lattice parameter of a Ni = 2.49 Å, which makes it an ideal substrate for the epitaxial growth of high-quality graphene layers ( a Gr = 2.46 Å) by hydrocarbon cracking. − Cr 2 O 3 is a corundum-type oxide, meaning that, when considered along the (0001) direction, it consists of a stack of different hexagonal planes that repeat themselves in an ordered way: one plane of oxygen with an in-plane lattice constant a O–O = 2.86 Å and two very close and shifted planes of chromium with an in-plane lattice constant a Cr–Cr = 4.96 Å. The hexagonal structures corresponding to the different ionic species are rotated by 90° with respect to each other. − …”

Section: Resultsmentioning

confidence: 99%

Graphene as an Ideal Buffer Layer for the Growth of High-Quality Ultrathin Cr₂O₃ Layers on Ni(111)

et al. 2019

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Metal−oxide nanostructures play a fundamental role in a large number of technological applications, ranging from chemical sensors to data storage devices. As the size of the devices shrinks down to the nanoscale, it is mandatory to obtain sharp and good quality interfaces. Here, it is shown that a two-dimensional material, namely, graphene, can be exploited as an ideal buffer layer to tailor the properties of the interface between a metallic substrate and an ultrathin oxide. This is proven at the interface between an ultrathin film of the magnetoelectric antiferromagnetic oxide Cr 2 O 3 and a Ni(111) single crystal substrate. The chemical composition of the samples has been studied by means of X-ray photoemission spectroscopy, showing that the insertion of graphene, which remains buried at the interface, is able to prevent the oxidation of the substrate. This protective action leads to an ordered and layer-by-layer growth, as revealed by scanning tunneling microscopy data. The structural analysis performed by lowenergy electron diffraction indicates that the oxide layer grown on graphene experiences a significant compressive strain, which strongly influences the surface electronic structure observed by scanning tunneling spectroscopy.

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“…Recent density functional theory calculation have also indicated that tensile strain on chromium oxide introduces both Cr and O vacancies ( Mi et al, 2018 ). These vacancies were predicted to introduce energy states below the conduction band, with Cr vacancies causing a significant decrease in the band gap.…”

Section: Discussionmentioning

confidence: 99%

Stress-Affected Oxygen Reduction Reaction Rates on UNS S13800 Stainless Steel

2022

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This work investigates the previously unexplored impact of tensile stress on oxygen reduction reaction (ORR) kinetics of a precipitation-hardened, stainless-steel fastener material, UNS S13800. ORR is known to drive localized and galvanic corrosion in aircraft assemblies and greater understanding of this reaction on structural alloys is important in forecasting component lifetime and service requirements. The mechano-electrochemical behavior of UNSS13800 was examined using amperometry to measure the reduction current response to tensile stress. Mechanical load cycles within the elastic regime demonstrated reversible electrochemical current shifts under chloride electrolyte droplets that exhibited a clear potential dependence. Strain ramping produced current peaks with a strain rate dependence, which was distinct from the chronoamperometric shifts during static tensile load conditions. Finally, mechanistic insight into the dynamic and static responses was obtained by deoxygenation, which demonstrated ORR contributions that were distinct from other reductive processes.

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The effects of strain and vacancy defects on the electronic structure of Cr2O3

Cited by 26 publications

References 38 publications

Structural Changes Induced by Heating in Sputtered NiO and Cr2O3 Thin Films as p-Type Transparent Conductive Electrodes

Structural Changes Induced by Heating in Sputtered NiO and Cr2O3 Thin Films as p-Type Transparent Conductive Electrodes

Graphene as an Ideal Buffer Layer for the Growth of High-Quality Ultrathin Cr₂O₃ Layers on Ni(111)

Stress-Affected Oxygen Reduction Reaction Rates on UNS S13800 Stainless Steel

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The effects of strain and vacancy defects on the electronic structure of Cr2O3

Cited by 26 publications

References 38 publications

Structural Changes Induced by Heating in Sputtered NiO and Cr2O3 Thin Films as p-Type Transparent Conductive Electrodes

Structural Changes Induced by Heating in Sputtered NiO and Cr2O3 Thin Films as p-Type Transparent Conductive Electrodes

Graphene as an Ideal Buffer Layer for the Growth of High-Quality Ultrathin Cr2O3 Layers on Ni(111)

Stress-Affected Oxygen Reduction Reaction Rates on UNS S13800 Stainless Steel

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Graphene as an Ideal Buffer Layer for the Growth of High-Quality Ultrathin Cr₂O₃ Layers on Ni(111)