Article

# Femtosecond Structural Dynamics in VO 2 during an Ultrafast Solid-Solid Phase Transition

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University of California San Diego, La Jolla, California 92093-0339, USA.
(Impact Factor: 7.51). 01/2002; 87(23):237401. DOI: 10.1103/PhysRevLett.87.237401
Source: PubMed

ABSTRACT

Femtosecond x-ray and visible pulses were used to probe structural and electronic dynamics during an optically driven, solid-solid phase transition in ${\mathrm{VO}}_{2}$. For high interband electronic excitation $($\sim${}5\ifmmode\times\else\texttimes\fi{}{10}^{21}{\mathrm{cm}}^{$-${}3})$, a subpicosecond transformation into the high- $T$, rutile phase of the material is observed, simultaneous with an insulator-to-metal transition. The fast time scale observed suggests that, in this regime, the structural transition may not be thermally initiated.

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Available from: Jeff A Squier, Oct 17, 2014
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• "In the recent monograph[10], it is stated that the metalinsulator transition in VO 2 has a combined nature, having the features of both Mott and Peierls transitions. Nonetheless, many experimental facts indicate that the transition might be initiated by an increase in the free charge carrier density (without heating to T = T t and without affecting the lattice, i.e. not under, for example, doping or pressure) under photo-generation[11], injection[12], or high-field generation at switching[13]. These results evidence that the electron-electron interaction is of importance for a correct description of the transition. "
##### Dataset: Vanadium Dioxide: Metal-Insulator Transition, Electrical Switching and Oscillations. A Review of State of the Art and Recent Progress
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ABSTRACT: http://arxiv.org/abs/1601.06246
Full-text · Dataset · Jan 2016
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• "Vanadium dioxide (VO 2 ) can undergo a fully reversible phase transition from metallic state to insulating state (MIT) at 68 °C, which is accompanied by a structural phase transition from monoclinic (P2 1 /c, M phase) to tetragonal (P4 2 /mnm, R phase) symmetry [1] [2]. With the phase transformation, both electrical and optical properties of VO 2 also change in four-order magnitude within subpicosecond [3]. So it can be used to fabricate smart windows, thermal switches, and sensors, etc. VO 2 (M) thin film is considered as one of the appropriate forms to realize these applications and the preparation of VO 2 films has been intensively investigated recently. "
##### Article: A Novel Inorganic Precipitation-Peptization Method for VO2 Sol and VO2 Nanoparticles Preparation: Synthesis, Characterization and Mechanism
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ABSTRACT: In this paper, a simple, safe and cost-saving precipitation-peptization method was proposed to prepare VO2 sol by using inorganic VOSO4-NH3⋅H2O-H2O2 reactants system in air under room temperature. In this process, VOSO4 was firstly precipitated to form VO(OH)2, then monometallic species of VO(O2)(OH)(-) were formed through the coordination between VO(OH)2 and H2O2. The rearrangement of VO(O2)(OH)(-) in a nonplanar pattern and intermolecular condensation reactions result in multinuclear species. Finally, VO2 sol is prepared through the condensation reactions between the multinuclear species. After drying the obtained sol at 40°C, VO2 xerogel exhibiting monoclinic crystal structure with the space group of C2/m was prepared. The crystal structure of VO2 nanoparticles was transferred to monoclinic crystal structure with the space group of P21/c (VO2(M)) by annealing the xerogel at 550°C. Both XRD and TEM analysis indicated that the nanoparticles possess good crystallinity with crystallite size of 34.5nm as estimated by Scherrer's method. These results suggest that the VO2 sol has been prepared successfully through the proposed simple method.
Full-text · Article · Sep 2015 · Journal of Colloid and Interface Science
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• "In this photoinduced solid state phenomenon, one should single out the case of the standard yet controversial oxide VO 2 which exhibits a pure 1st order phase transition. Indeed, as reported recently by various authors, the photoinduced phase transition by femtosecond laser pulses in VO 2 has allowed shedding light not only on the so long disputed nature of the transition itself, distinguishing hence the Mott–Hubbard-like transition from the electron trapping in homopolar bonds, but also on its dynamic and the duration of the phase transition itself which was found to be of about 180 fs [18] [19]. The additional complementary recent work of Lysenko et al. [20] indicated that, upon a laser excitation, an instantaneous response in the transient reflectivity and transmission was observed followed by a relatively longer relaxation process. "
##### Article: Photoinduced Electron Spin Resonance Phenomenon in a-Cr2O3 Nanospheres
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ABSTRACT: The photoinduced phenomenon in 𝛼-Cr2O3 nanoscaled spherical particles was investigated in the temperature range of 150 up to 315 K. An X-band electron-spin resonance spectrometry was employed to probe the magnetic behavior in 𝛼-Cr2O3 under an IR illumination in the nanosecond regime. The photoinduced effect on both low and high field ESR signals appears above 280 K and is remarkably enhanced just below Neel temperature ´ 𝑇N. Such a photoinduced ESR phenomenon disappears in a reproducible way in the paramagnetic insulating state which occurs above 𝑇N of crystalline 𝛼-Cr2O3. In the antiferromagnetic phase, that is, below 𝑇N, the shift of the low field absorption could be attributed to the interaction of the light with specific Cr3+ ions located in strongly distorted sites correlated to strong ligand-field effect.
Full-text · Article · Jan 2015 · Journal of Nanomaterials