Atomic and electronic structures of charge-doping VO<sub>2</sub>: first-principles calculations

Chen, Lanli; Cui, Yuanyuan; Luo, Hongjie; Gao, Yanfeng

doi:10.1039/d0ra02420a

Cited by 19 publications

(10 citation statements)

References 45 publications

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“…For electron doping, on the other hand, the transition temperature decreases only by a few K per additional electron, ranging between −2.2 K and −4.3 K per 10 21 cm –3 electron density increase (in the range from 0 to 3.1 × 10 21 cm –3 ). These findings are in good agreement with the ones in ref . The relaxation of the structure has a rather small effect on the transition temperature compared to the charge-doped systems at neutral geometry, suggesting that atomistic structure rearrangements are not the driving force for the transition temperature change.…”

Section: Resultssupporting

confidence: 92%

“…In order to better understand the interplay between charge density and dopant ion in the context of the VO 2 thermochromism, we first studied the effect of bare charge doping on transition temperatures and light absorption in VO 2 . In ref , Chen et al have investigated the effect of charge doping on the former in detail. In accordance with their results, we found that electron and hole doping both reduce T MIT , with the effect of the latter being much stronger as shown in Figure a.…”

Section: Resultsmentioning

confidence: 99%

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The Origin of the Thermochromic Property Changes in Doped Vanadium Dioxide

Koch

Chaker

2022

ACS Appl. Mater. Interfaces

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Vanadium dioxide is a promising material for novel smart window applications due to its reversible metal–insulator transition which is accompanied by a change in its optical properties. The transition temperature (T MIT) can be controlled via elemental doping, but the reduction of T MIT is generally coupled with a decrease of the optical contrast between the two phases. To better understand how the contrast is fundamentally connected to T MIT, the thermochromic properties of doped VO2 were theoretically investigated across the metal–insulator transition from first principles. Different dopants and their interaction with the VO2 host structure as well as different modes of doping were studied in detail. It was found that the transition temperature change is mainly related to the stabilization of the high-temperature metallic phase due to lattice deformations which are caused by the presence of the dopant ion. Inherent limitations to the thermochromic performance of VO2 substitutionally doped by the replacement of vanadium cations with other species were found, and alternative approaches were proposed. Specifically, a charge-neutral substitution of oxygen or an oxygen substitution in combination with interstitial doping without net charge transfer between the dopant atoms and VO2 were identified as promising avenues to ensure a low T MIT and no loss of optical contrast in vanadia-based smart window materials.

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Section: Resultssupporting

confidence: 92%

Section: Resultsmentioning

confidence: 99%

The Origin of the Thermochromic Property Changes in Doped Vanadium Dioxide

Koch

Chaker

2022

ACS Appl. Mater. Interfaces

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“…The higher intensity presents an additional contribution from the acceptor level of Co 2+ 3d (∼1 eV), as marked in the diagram, indicating a higher orbital occupancy with more trapped holes induced by Co 3d –V 3d coupling . It was previously reported that the band structure could be tuned by carrier localization . Carriers can be trapped at V or O sites to form V (4‑ n )+ –V 4+ pairs ( n = 1, 2, or 3) .…”

Section: Resultsmentioning

confidence: 84%

“…49 It was previously reported that the band structure could be tuned by carrier localization. 50 Carriers can be trapped at V or O sites to form V (4-n)+ −V 4+ pairs (n = 1, 2, or 3). 8 The V 3d band shift indicates that a V 5+ −V 4+ pair in the Co-doped VO 2 is induced by localized holes and pushes the Fermi level closer to the valence band.…”

Section: Resultsmentioning

confidence: 99%

Tuning Phase Transition and Thermochromic Properties of Vanadium Dioxide Thin Films via Cobalt Doping

Geng

Chang

Fan

et al. 2022

ACS Appl. Mater. Interfaces

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Vanadium dioxide (VO2) featuring a distinct thermally triggered phase transition is regarded as the most attractive thermochromic material for smart window applications. However, the high transition temperature (∼67 °C) and moderate luminous transmittance (<50%) of the pristine VO2 circumvent room temperature applications. In this work, epitaxial cobalt-doped VO2 thin films were fabricated to tailor the electric and optical properties on a c-plane sapphire substrate. At the highest doping concentration of 10%, the transition temperature of VO2 is reduced to 44 °C, accompanied by a high luminous transmittance of 79% for single-element Co-doped VO2. The roles of cobalt doping and detailed band variation are fully explained experimentally and by modeling (DFT calculation), respectively. Furthermore, the dramatically increased carrier concentration in cobalt-doped VO2 underscores the promising future of cobalt-doped VO2 unveiled by temperature-dependent Hall effect measurement.

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“…Since Morin reported observing the metal-to-insulator transition (MIT) of VO 2 in 1959 1 , VO 2 has been widely studied to understand the origin of its MIT [2][3][4][5][6][7] and to use it in practical applications including smart windows, batteries, transistors, ultrafast switches, and gas sensors [8][9][10][11][12][13][14][15] . The MIT of VO 2 can be induced by different factors such as heat, an electric field, doping, oxygen vacancy, photons, and a magnetic field 1,[5][6][7][16][17][18][19][20] . A typical critical temperature (T c ) of the MIT of VO 2 is approximately 68 °C 5 .…”

Section: Decoupling the Metal Insulator Transition And Crystal Field mentioning

confidence: 99%

Decoupling the metal insulator transition and crystal field effects of VO2

Hwang

Park

Yeo

et al. 2021

Sci Rep

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VO2 is a highly correlated electron system which has a metal-to-insulator transition (MIT) with a dramatic change of conductivity accompanied by a first-order structural phase transition (SPT) near room temperature. The origin of the MIT is still controversial and there is ongoing debate over whether an SPT induces the MIT and whether the Tc can be engineered using artificial parameters. We examined the electrical and local structural properties of Cr- and Co-ion implanted VO2 (Cr-VO2 and Co-VO2) films using temperature-dependent resistance and X-ray absorption fine structure (XAFS) measurements at the V K edge. The temperature-dependent electrical resistance measurements of both Cr-VO2 and Co-VO2 films showed sharp MIT features. The Tc values of the Cr-VO2 and Co-VO2 films first decreased and then increased relative to that of pristine VO2 as the ion flux was increased. The pre-edge peak of the V K edge from the Cr-VO2 films with a Cr ion flux ≥ 1013 ions/cm2 showed no temperature-dependent behavior, implying no changes in the local density of states of V 3d t2g and eg orbitals during MIT. Extended XAFS (EXAFS) revealed that implanted Cr and Co ions and their tracks caused a substantial amount of structural disorder and distortion at both vanadium and oxygen sites. The resistance and XAFS measurements revealed that VO2 experiences a sharp MIT when the distance of V–V pairs undergoes an SPT without any transitions in either the VO6 octahedrons or the V 3d t2g and eg states. This indicates that the MIT of VO2 occurs with no changes of the crystal fields.

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Atomic and electronic structures of charge-doping VO₂: first-principles calculations

Abstract: The controllable phase transition temperature in charge doping VO2 is coupled with changes in the atomic and electronic structures. The current results provide a variable way to tune the VO2 phase transition temperature through charge doping.

Cited by 19 publications

References 45 publications

The Origin of the Thermochromic Property Changes in Doped Vanadium Dioxide

The Origin of the Thermochromic Property Changes in Doped Vanadium Dioxide

Tuning Phase Transition and Thermochromic Properties of Vanadium Dioxide Thin Films via Cobalt Doping

Decoupling the metal insulator transition and crystal field effects of VO2

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Atomic and electronic structures of charge-doping VO2: first-principles calculations

Abstract: The controllable phase transition temperature in charge doping VO2 is coupled with changes in the atomic and electronic structures. The current results provide a variable way to tune the VO2 phase transition temperature through charge doping.

Cited by 19 publications

References 45 publications

The Origin of the Thermochromic Property Changes in Doped Vanadium Dioxide

The Origin of the Thermochromic Property Changes in Doped Vanadium Dioxide

Tuning Phase Transition and Thermochromic Properties of Vanadium Dioxide Thin Films via Cobalt Doping

Decoupling the metal insulator transition and crystal field effects of VO2

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Product

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Atomic and electronic structures of charge-doping VO₂: first-principles calculations