Sequential Electronic and Structural Transitions in VO<sub>2</sub> Observed Using X‐ray Absorption Spectromicroscopy

Kumar, Suhas; Strachan, John Paul; Pickett, Matthew D.; Bratkovsky, A. M.; Nishi, Yoshio; Williams, R. Stanley

doi:10.1002/adma.201402404

Cited by 84 publications

(67 citation statements)

References 46 publications

(121 reference statements)

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“…O1s to O2p states, in which two distinct features of the t 2g and e g peaks reflected the unoccupied states [26,27]. The intensity ratio of t 2g /e g decreased substantially with…”

Section: (D) Presented the Transitions Frommentioning

confidence: 98%

Sequential insulator-metal-insulator phase transitions of VO2 triggered by hydrogen doping

Shi¹,

Wang²,

Fan³

et al. 2017

Phys. Rev. B

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We report modulation of a reversible phase transition in VO 2 films by hydrogen doping. Metallic and insulating phases are successively observed at room temperature as the doping concentration increases. The polarized charges induced by doped hydrogens gradually occupy V3d-O2p hybridized orbitals and consequently modulate the filling of the VO 2 crystal conduction band-edge states, which eventually become saturated and therefore evolve into new valence band-edge states. A clear linear relationship between H-concentration and V3d orbital occupancy were found.These results suggest the exceptional sensitivity of VO 2 electronic properties to electron concentration and orbital occupancy, providing key information for the phase transition mechanism.

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“…O1s to O2p states, in which two distinct features of the t 2g and e g peaks reflected the unoccupied states [26,27]. The intensity ratio of t 2g /e g decreased substantially with…”

Section: (D) Presented the Transitions Frommentioning

confidence: 98%

Sequential insulator-metal-insulator phase transitions of VO2 triggered by hydrogen doping

Shi¹,

Wang²,

Fan³

et al. 2017

Phys. Rev. B

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“…The vanadium K-edge XANES high-resolution spectroscopy has been shown to have the sensitivity to probe the local structure changes associated with the MIT transition [52]. Moreover, a local probe such as XANES may investigate simultaneously both the MIT and the SPT, monitoring the local behaviour of VO 2 films at the O K-edge [53].…”

Section: Mesoscience and The Phase Separation Scenario In Correlated mentioning

confidence: 99%

“…Recent results using X-ray absorption spectromicroscopy [53] showed that it is possible to induce an electronic transition without inducing a structural transition in thin film of VO 2 during a heating-cooling cycle. This experiment is an additional demonstration of the relevance of used techniques with high spectral, time and spatial resolution, to accurately study inhomogeneous media such as phase separated materials and with complex multi-dimensional phase diagrams.…”

Section: Mesoscience and The Phase Separation Scenario In Correlated mentioning

confidence: 99%

Phase Separations in Highly Correlated Materials

Marcelli

2016

Acta Phys. Pol. A

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The X-ray absorption near edge structure spectroscopy is a unique powerful local and fast experimental method to study complex systems since it probes the nanoscale structure around selected atoms giving evidence for different local and instantaneous phases present in multiscale highly correlated granular systems. Transition metals and rare earth oxides like manganites, cuprates or pnictides superconductors show a rich variety of different competing structural, electronic and magnetic phases, which spatially coexist forming complex lattice textures. Many recent experimental data have pointed out the presence of arrested phase separation and the interplay of different phases occurring from nano-to micrometer-scale. This scenario opens the possibility to manipulate the mesoscopic phases to get new material functionalities. Therefore there is increasing need to develop methods to probe morphology and phase distribution at multiple length scales. Actually, combining X-ray imaging at high spatial resolution with µ-XANES spectroscopy both mesoscale, nanoscale and atomic structural changes can be identified. The µ-XANES spectroscopy technique is rapidly growing to investigate adaptive matter, high temperature superconductors, complex materials showing arrested phase separation at the mesoscale. IntroductionIt is well known that phase separation occurs where two or more phases with comparable free energies coexist giving two or more macroscopic phases each one with a large coherence length, however there is growing scientific interest for the case of arrested phase separations in transition metal oxides where two or more phases form complex textures extending in the mesoscale between the atomic scale and the macroscopic world, made of small domains with a size ranging from nanoscale to micron-scale. The mesoscale phase separation leads to strong anomalies or dramatic changes of system properties and material functionality. Clear anomalies are observed in the behaviour of different observable quantities such as the resistivity and the optical transmission [1,2]. The origin of the mesoscale phase separation phenomenon responsible for a variety of unusual phenomena is due to the appearance of voxels of competing thermodynamic phases inside a host phase [3][4][5][6]. Transition metals and rare earth oxides, as for example high temperature superconductors, as cuprates or pnictides present multiple electronic states with different orbital symmetries at the Fermi energy and competing anisotropic Coulomb, magnetic and electron-lattice short range interactions together with long range Coulomb and elastic interaction, giving complex lattice architectures and a rich variety of different coexisting electronic and magnetic phases. Their interplay plays a key role in colossal magnetoresistance materials [7,8], ferroelectrics [9,10] and in high temperature superconductors (HTS) showing arrested phase separation at mesoscopic or nanoscopic length scales [11][12][13][14][15].

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“…3-6 Some of the important scientific issues recently addressed include the nature and sequence of the transitions, 7,8 effect of surface charges, 9,10 role of joule heating during resistance switching, 11,12 phase diagram of the transitions, 13 etc. There have been debates and contradicting results on several of these issues.…”

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confidence: 99%

“…This is very consistent with our previous experimental result using a more direct and detailed mapping of the two transitions in the same film of VO2 used here. 8 To better compare the transitions observed in the infrared, visible and x-ray transmission, and the resistance, we used the 2-dimensional Bruggeman effective medium approximation (EMA) for percolative media to calculate the macroscopic resistance (black curve in Figure 3a) by parametrically varying the volume fraction of the component phases with different resistivities (using terminal resistance values from Figure 1b for heating and cooling braches separately). [29][30][31] We then use the normalized transmission of Figure 1b as indicative of the phase fractions (Φ) measured by infrared and visible lights and map them to the resistance of the film at the corresponding temperatures ( Figure 3a).…”

mentioning

confidence: 99%

The phase transition in VO2 probed using x-ray, visible and infrared radiations

Kumar

Strachan

Kilcoyne

et al. 2016

Applied Physics Letters

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Sequential Electronic and Structural Transitions in VO₂ Observed Using X‐ray Absorption Spectromicroscopy

Cited by 84 publications

References 46 publications

Sequential insulator-metal-insulator phase transitions of VO2 triggered by hydrogen doping

Sequential insulator-metal-insulator phase transitions of VO2 triggered by hydrogen doping

Phase Separations in Highly Correlated Materials

The phase transition in VO2 probed using x-ray, visible and infrared radiations

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Sequential Electronic and Structural Transitions in VO2 Observed Using X‐ray Absorption Spectromicroscopy

Cited by 84 publications

References 46 publications

Sequential insulator-metal-insulator phase transitions of VO2 triggered by hydrogen doping

Sequential insulator-metal-insulator phase transitions of VO2 triggered by hydrogen doping

Phase Separations in Highly Correlated Materials

The phase transition in VO2 probed using x-ray, visible and infrared radiations

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Sequential Electronic and Structural Transitions in VO₂ Observed Using X‐ray Absorption Spectromicroscopy