Growth and the structure of epitaxial<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">VO</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>at the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">TiO</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>(110) surface

Sambi, Mauro; Sangiovanni, Guido; Granozzi, G.; Parmigiani, F.

doi:10.1103/physrevb.55.7850

Cited by 92 publications

(45 citation statements)

References 21 publications

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“…A new V 2p 3/2 peak at 516.4-516.5 eV appears in the reaction mixture pointing to the partial reduction of V 5+ to V 4+ even at room temperature. It should be noted that in the highly cited studies [57][58][59][60][61] [20,[62][63][64][65][66][67][68]. These numbers are in good agreement with our data.…”

Section: In Situ Nap Xps Xanes and Tpr Studysupporting

confidence: 83%

Selective oxidation of methanol to form dimethoxymethane and methyl formate over a monolayer V2O5/TiO2 catalyst

Каичев

Popova

Chesalov

et al. 2014

Journal of Catalysis

130

150

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address: vvk@catalysis.ru (V.V. Kaichev). A B S T R A C TThe methanol oxidation over highly dispersed vanadium oxide supported on TiO 2 (anatase) has been investigated by in situ Fourier transform infrared spectroscopy (FTIR), near ambient pressure X-ray photoelectron spectroscopy (NAP XPS), X-ray absorption near edge structure (XANES), and temperature-programmed reaction spectroscopy. The data were complimented with kinetics measurements in a flow reactor. It was found that at low temperatures dimethoxymethane competes with methyl formate, whereas the production of formaldehyde is greatly inhibited. FTIR shows the presence of non-dissociatively adsorbed molecules of methanol, as well as adsorbed methoxy, dioximethylene, and formate species under reaction conditions. According to the NAP XPS and XANES data, the reaction involves the reversible reduction of V 5+ cations, pointing that the vanadia lattice oxygen participates in the methanol oxidation through the classical Mars-van Krevelen mechanism. The detailed mechanism of the methanol oxidation on vanadia catalysts is discussed.

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Section: In Situ Nap Xps Xanes and Tpr Studysupporting

confidence: 83%

Selective oxidation of methanol to form dimethoxymethane and methyl formate over a monolayer V2O5/TiO2 catalyst

Каичев

Popova

Chesalov

et al. 2014

Journal of Catalysis

130

150

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“…We began with the procedure described by Sambi et al for producing epitaxial VO 2 thin films on TiO 2 (110). [17][18][19][20][21] The key aspect of this procedure was the deposition of 0.2-0.5 monolayers (ML) of amorphous vanadium metal at room temperature followed by a 2 minute anneal at 423 K in 7.5×10 -7 -1.5×10 -6 Torr of oxygen during which it transforms into an epitaxial VO 2 layer. One ML corresponds to 5.2×10 14 vanadium atoms / cm 2 for growth on TiO 2 (110).…”

Section: -13mentioning

confidence: 99%

Epitaxial growth of VO2 by periodic annealing

Tashman

Lee

Paik

et al. 2014

Applied Physics Letters

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We report the growth of ultrathin VO 2 films on rutile TiO 2 (001) substrates via reactive molecular-beam epitaxy. The films were formed by the cyclical deposition of amorphous vanadium and its subsequent oxidation and transformation to VO 2 via solid-phase epitaxy.Significant metal-insulator transitions were observed in films as thin as 2.3 nm, where a resistance change ΔR/R of 25 was measured. Low angle annular dark field scanning transmission electron microscopy was used in conjunction with electron energy loss spectroscopy to study the film/substrate interface and revealed the vanadium to be tetravalent and the titanium interdiffusion to be limited to 1.6 nm. Page 4 of 25The huge metal-insulator transition (MIT) exhibited by VO 2 in the vicinity of roomtemperature has made it a material of interest for uncooled microbolometer arrays, 1 gas sensing, 2 optical limiting, 3 and most recently MIT transistors. 4,5 In bulk single crystals this MIT occurs at a transition temperature (T c ) of 340 K and is accompanied by a change in structure from a hightemperature tetragonal form, to a low-temperature monoclinic form. 6 The change in resistivity through this transition in bulk VO 2 single crystals has been measured to be five orders of magnitude with a temperature hysteresis 0.5-1 K. 7 The change in resistivity in thick films (>100 nm) can be as high as four orders of magnitude, [8][9][10] but in thin films (<10 nm) is less than three orders of magnitude in all reports to date. 11-13While VO 2 presents an opportunity for emergent switching devices and sensors, its large carrier concentration (~10 In this paper we describe a process for the growth of ultrathin VO 2 films by reactive molecular-beam epitaxy (MBE) and show that they exhibit clear MITs in films as thin as 2.3 nm.We investigate the properties of these films with four-circle x-ray diffraction (XRD), low-angle annular dark field (LAADF) scanning transmission electron microscopy (STEM), electron energy loss spectroscopy (EELS), and electronic transport measurements. We also describe a standardized method for calculating the magnitude, hysteresis, and T c of these transitions using Savitsky-Golay smoothing derivatives. 16 All films in this paper were grown by MBE in a Veeco Gen10. X-ray diffraction spectra were collected with a Rigaku Smartlab system utilizing Cu Κ α1 radiation with a 220 Ge twobounce incident-beam monochromator and a 220 Ge two-bounce diffraction side analyzer crystal. STEM images were taken with an FEI Tecnai G 2 F20. VO 2 film thicknesses were calculated with data from Rutherford backscattering spectrometry (RBS) assuming the calibration films had bulk VO 2 density. Electrical transport data was taken using the standard four-contact van der Pauw method in a Quantum Design Physics Property Measurement System (PPMS) with contacts made using gold wire and silver paint. All growth temperatures were measured using a thermocouple in the substrate cavity, but not in contact with the substrate.During growth the film was monitored using reflection ...

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“…Recently, in an effort to better understand the relationships between the structure and reactivity of supported vanadia catalysts several groups have studied model systems composed of vapor-deposited vanadia films supported on well-defined metal oxide single crystal surfaces including TiO 2 (110) and CeO 2 (111) [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31]. In the studies of vanadia films on TiO 2 (110) it has been found that vapor deposition of vanadium metal, either in the presence of a background of O 2 or followed by annealing in O 2 , produces vanadia films that predominantly contain V +3 or mixtures of V +3 and V +4 for O 2 pressures less than 10 -6 Torr [22,23,29].…”

Section: Introductionmentioning

confidence: 99%

“…In the studies of vanadia films on TiO 2 (110) it has been found that vapor deposition of vanadium metal, either in the presence of a background of O 2 or followed by annealing in O 2 , produces vanadia films that predominantly contain V +3 or mixtures of V +3 and V +4 for O 2 pressures less than 10 -6 Torr [22,23,29]. The reactivity of these films has been studied using TPD of methanol [12,13].…”

Section: Introductionmentioning

confidence: 99%

Reactivity of monolayer V2O5 films on TiO2(110) produced via the oxidation of vapor-deposited vanadium

2003

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The growth, and reactivity of monolayer V 2 O 5 films supported on TiO 2 (110) produced via the oxidation of vapor-deposited vanadium were studied using X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD). Oxidation of vapor-deposited vanadium in 10 -7 Torr of O 2 at 600 K produced vanadia films that contained primarily V +3 , while oxidation in 10 -3 Torr at 400 K produced films that contained primarily V +5 . The reactivity of the supported vanadia layers for the oxidation of methanol to formaldehyde was studied using TPD. The activity for this reaction was found to be a function of the oxidation state of the vanadium cations in the film. AbstractThe growth, and reactivity of monolayer V 2 O 5 films supported on TiO 2 (110) produced via the oxidation of vapor-deposited vanadium were studied using X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD).Oxidation of vapor-deposited vanadium in 10 -7 Torr of O 2 at 600 K produced vanadia films that contained primarily V +3 , while oxidation in 10 -3 Torr at 400 K produced films that contained primarily V +5 . The reactivity of the supported vanadia layers for the oxidation of methanol to formaldehyde was studied using TPD. The activity for this reaction was found to be a function of the oxidation state of the vanadium cations in the film.

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Growth and the structure of epitaxialVO2at theTiO2(110) surface

Cited by 92 publications

References 21 publications

Selective oxidation of methanol to form dimethoxymethane and methyl formate over a monolayer V2O5/TiO2 catalyst

Selective oxidation of methanol to form dimethoxymethane and methyl formate over a monolayer V2O5/TiO2 catalyst

Epitaxial growth of VO2 by periodic annealing

Reactivity of monolayer V2O5 films on TiO2(110) produced via the oxidation of vapor-deposited vanadium

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