Formation of Highly Ordered VO<sub>2</sub> Nanotubular/Nanoporous Layers and Their Supercooling Effect in Phase Transitions

Yang, Yang; Lee, Ki-Young; Zobel, Mirijam; Mačković, Mirza; Unruh, Tobias; Spiecker, Erdmann; Schmuki, Patrik

doi:10.1002/adma.201200073

Cited by 25 publications

(25 citation statements)

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“…11,[65][66][67] Consequently it is of great importance to develop efficient methods to prepare such nanoparticles in large quantities and over extended surfaces. In fact, there have been numerous prior studies on VO 2 -based nanoparticles, and recent investigations have been conducted with hydrothermal/solvothermal/colloidal techniques, 27,49,50,64, vapor transport, 56,[109][110][111][112][113][114][115] anodization, 116 polymer-assisted deposition, 117,118 and templating. 29,119 References to earlier studies on the manufacturing of nanostructured VO 2 -based materials can be found elsewhere.…”

Section: Introductionmentioning

confidence: 99%

Thermochromic VO2 nanorods made by sputter deposition: Growth conditions and optical modeling

Namura

Suzuki

et al. 2013

Journal of Applied Physics

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Thermochromic VO 2 nanorods made by sputter deposition: Growth conditions and optical modeling. Reactive dc magnetron sputtering onto glass-based substrates yielded deposits of thermochromic VO 2 with well-developed nanorods and nanowires. Their formation was promoted by high substrate temperature (above ~500 °C), sufficient film thickness, proper inlet of the reactive gas, dispersed gold "seeds" and pronounced substrate roughness. Rutherford back scattering ascertained mass thicknesses, scanning electron microscopy depicted the nanostructures, and glancing incidence Xray diffraction proved that single-phase VO 2 was normally formed. Journal of Applied PhysicsSpectrophotometric measurements of total and diffuse transmittance and reflectance on VO 2 thin films, at room temperature and ~100 °C, allowed us to determine complex dielectric functions below and above the "critical" temperature for thermochromic switching (~68 °C). These data were then used in computations based on the Bruggeman effective medium theory applied to randomly oriented prolate spheroidal structural units to derive the optical properties of the deposits.Experimental and computed data on spectral absorptance were found to be in good qualitative agreement.

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Section: Introductionmentioning

confidence: 99%

Thermochromic VO2 nanorods made by sputter deposition: Growth conditions and optical modeling

Namura

Suzuki

et al. 2013

Journal of Applied Physics

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“…Moreover, scaling VO 2 particles to nanoscale offers the possibility to further enhance its thermochromic performance at a moderate τ c . Several chemical and physical techniques have been reported to construct nanostructures of thermochromic VO 2 , including hydrothermal, magnetron sputtering, CVD, PVD, sol–gel, confined‐space combustion method, electrochemical and solution methods . Among them, vapor deposition is an efficient method for high quality VO 2 ‐film fabrication, but the equipment required for the film deposition is usually complex and expensive; a solution‐based deposition process is more cost effective, high‐yielding, and flexible, but it always suffers from multiple‐steps, lower purity, and small‐scale production .…”

Section: Introductionmentioning

confidence: 99%

Hydrothermal Synthesis of VO₂ Polymorphs: Advantages, Challenges and Prospects for the Application of Energy Efficient Smart Windows

Magdassi

Gao

et al. 2017

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Vanadium dioxide (VO ) is a widely studied inorganic phase change material, which has a reversible phase transition from semiconducting monoclinic to metallic rutile phase at a critical temperature of τ ≈ 68 °C. The abrupt decrease of infrared transmittance in the metallic phase makes VO a potential candidate for thermochromic energy efficient windows to cut down building energy consumption. However, there are three long-standing issues that hindered its application in energy efficient windows: high τ , low luminous transmittance (T ), and undesirable solar modulation ability (ΔT ). Many approaches, including nano-thermochromism, porous films, biomimetic surface reconstruction, gridded structures, antireflective overcoatings, etc, have been proposed to tackle these issues. The first approach-nano-thermochromism-which is to integrate VO nanoparticles in a transparent matrix, outperforms the rest; while the thermochromic performance is determined by particle size, stoichiometry, and crystallinity. A hydrothermal method is the most common method to fabricate high-quality VO nanoparticles, and has its own advantages of large-scale synthesis and precise phase control of VO . This Review focuses on hydrothermal synthesis, physical properties of VO polymorphs, and their transformation to thermochromic VO (M), and discusses the advantages, challenges, and prospects of VO (M) in energy-efficient smart windows application.

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“…The phase transitions were observed at 70 ˚C and 45 ˚C for heating and cooling cycles, respectively 53. Cheng et al54 reported high-resolution transmission electron microscopy imaging of a phase transition in a VO 2 rod, activated in situ by a high intensity electron beam.Although recent TEM studies have revealed some aspects of structural details of the phase transition, the atomic scale mechanisms of the phase transition in doped VO 2 remains unclear.…”

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Atomic Origins of Monoclinic-Tetragonal (Rutile) Phase Transition in Doped VO₂ Nanowires

et al. 2015

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There has been long-standing interest in tuning the metal-insulator phase transition in vanadium dioxide (VO2) via the addition of chemical dopants. However, the underlying mechanisms by which doping elements regulate the phase transition in VO2 are poorly understood. Taking advantage of aberration-corrected scanning transmission electron microscopy, we reveal the atomistic origins by which tungsten (W) dopants influence the phase transition in single crystalline WxV1-xO2 nanowires. Our atomically resolved strain maps clearly show the localized strain normal to the (122̅) lattice planes of the low W-doped monoclinic structure (insulator). These strain maps demonstrate how anisotropic localized stress created by dopants in the monoclinic structure accelerates the phase transition and lead to relaxation of structure in tetragonal form. In contrast, the strain distribution in the high W-doped VO2 structure is relatively uniform as a result of transition to tetragonal (metallic) phase. The directional strain gradients are furthermore corroborated by density functional theory calculations that show the energetic consequences of distortions to the local structure. These findings pave the roadmap for lattice-stress engineering of the MIT behavior in strongly correlated materials for specific applications such as ultrafast electronic switches and electro-optical sensors.

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Formation of Highly Ordered VO₂ Nanotubular/Nanoporous Layers and Their Supercooling Effect in Phase Transitions

Abstract: The fabrication of self-organized VO(2) nanotubular/nanoporous layers is demonstrated by self-organizing anodization, followed by a suitable heat treatment. These VO(2) layers show a reversible metal to insulator transition (MIT) at 70 and 44 °C, when heating and cooling, respectively.

Cited by 25 publications

References 32 publications

Thermochromic VO2 nanorods made by sputter deposition: Growth conditions and optical modeling

Thermochromic VO2 nanorods made by sputter deposition: Growth conditions and optical modeling

Hydrothermal Synthesis of VO₂ Polymorphs: Advantages, Challenges and Prospects for the Application of Energy Efficient Smart Windows

Atomic Origins of Monoclinic-Tetragonal (Rutile) Phase Transition in Doped VO₂ Nanowires

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Formation of Highly Ordered VO2 Nanotubular/Nanoporous Layers and Their Supercooling Effect in Phase Transitions

Abstract: The fabrication of self-organized VO(2) nanotubular/nanoporous layers is demonstrated by self-organizing anodization, followed by a suitable heat treatment. These VO(2) layers show a reversible metal to insulator transition (MIT) at 70 and 44 °C, when heating and cooling, respectively.

Cited by 25 publications

References 32 publications

Thermochromic VO2 nanorods made by sputter deposition: Growth conditions and optical modeling

Thermochromic VO2 nanorods made by sputter deposition: Growth conditions and optical modeling

Hydrothermal Synthesis of VO2 Polymorphs: Advantages, Challenges and Prospects for the Application of Energy Efficient Smart Windows

Atomic Origins of Monoclinic-Tetragonal (Rutile) Phase Transition in Doped VO2 Nanowires

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Formation of Highly Ordered VO₂ Nanotubular/Nanoporous Layers and Their Supercooling Effect in Phase Transitions

Hydrothermal Synthesis of VO₂ Polymorphs: Advantages, Challenges and Prospects for the Application of Energy Efficient Smart Windows

Atomic Origins of Monoclinic-Tetragonal (Rutile) Phase Transition in Doped VO₂ Nanowires