Photoemission study of hydrogen adsorption on vanadium dioxide near the semiconductor-metal phase transition

Bermudez, V. M.; Williams, Richard; Long, James P.; Reed, Rolf K.; Klein, Philipp H.

doi:10.1103/physrevb.45.9266

Cited by 34 publications

(19 citation statements)

References 18 publications

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“…Therefore, V 2 O x thin films are gradually reduced owing to the generation of more oxygen vacancies. This partial reduction leads to an increase in the V3d electron density [ 52 ]. Furthermore, oxygen vacancies in V 2 O x can cause localisation excess electrons in unfilled 3d orbitals which can explain the absorption peak near to the ultraviolet band observed in Figure 4 [ 37 ].…”

Section: Resultsmentioning

confidence: 99%

Thermally Stable Solution Processed Vanadium Oxide as a Hole Extraction Layer in Organic Solar Cells

et al. 2016

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Low-temperature solution-processable vanadium oxide (V2Ox) thin films have been employed as hole extraction layers (HELs) in polymer bulk heterojunction solar cells. V2Ox films were fabricated in air by spin-coating vanadium(V) oxytriisopropoxide (s-V2Ox) at room temperature without the need for further thermal annealing. The deposited vanadium(V) oxytriisopropoxide film undergoes hydrolysis in air, converting to V2Ox with optical and electronic properties comparable to vacuum-deposited V2O5. When s-V2Ox thin films were annealed in air at temperatures of 100 °C and 200 °C, OPV devices showed similar results with good thermal stability and better light transparency. Annealing at 300 °C and 400 °C resulted in a power conversion efficiency (PCE) of 5% with a decrement approximately 15% lower than that of unannealed films; this is due to the relative decrease in the shunt resistance (Rsh) and an increase in the series resistance (Rs) related to changes in the oxidation state of vanadium.

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Section: Resultsmentioning

confidence: 99%

Thermally Stable Solution Processed Vanadium Oxide as a Hole Extraction Layer in Organic Solar Cells

et al. 2016

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“…The increased bonding character would result in a decrease in the energy of the O 2p π band. 38 Water may similarly induce relaxation through its interaction with the VO 2 surface, which could also increase V-O 2p π-orbital overlap, resulting in a similar change in the valence band.…”

Section: Please Cite This Article As Doi:101063/15138959mentioning

confidence: 99%

Water adsorption on vanadium oxide thin films in ambient relative humidity

Goodacre

Blum

Büchner

et al. 2020

The Journal of Chemical Physics

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In this work, ambient pressure X-ray photoelectron spectroscopy (APXPS) is used to study the initial stages of water adsorption on vanadium oxide surfaces. V 2p, O 1s, C 1s and valence band XPS spectra were collected as a function of relative humidity in a series of isotherm and isobar experiments. Experiments were carried out on two VO 2 thin films on TiO 2 (100) substrates, prepared with different surface cleaning procedures. Hydroxyl and molecular water surface species were identified, with up to 0.5 ML hydroxide present at the minimum relative humidity, and a consistent molecular water adsorption onset occurring around 0.01 % relative humidity. The work function was found to increase with increasing relative humidity, suggesting that surface water and hydroxyl species are oriented with the hydrogen atoms directed away from the surface. Changes in the valence band were also observed as a function of relative humidity. Results were similar to those observed in APXPS experiments on other transition metal oxide surfaces, suggesting H 2 O-OH and H 2 O-H 2 O surface complex formation plays an important role in the oxide wetting process and water dissociation. Compared to polycrystalline vanadium metal, these vanadium oxide films generate less hydroxide and appear to be more favorable for molecular water adsorption.

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“…[17][18][19][20][21] Using ultraviolet photoemission spectroscopy (UPS) and ultraviolet optical reflectance measurements, Shin et al 19) have provided detailed information about the valence-band and conduction-band structures in the metallic and insulating phases. They concluded that the importance of the itinerant Ã electrons to screen the d k electrons in the metallic phase was recognized.…”

Section: Introductionmentioning

confidence: 99%

Temperature-Dependent Electronic Structure of VO₂in the Insulating Phase

2002

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We have studied the temperature-dependent electronic structure of VO 2 in the insulating phase. The V 3d and O 2p bands become broader and their band edges are shifted toward the Fermi level (E F ) with increasing temperature. The V 2p and O 1s core-level spectra also show a similar temperature dependence. These observations combined with optical spectra indicate that the position of E F relative to the conduction-band minimum is fixed and that the band gap changes mainly below E F . We also point out the possibility that electron-phonon interaction plays an important role in the temperature dependence of spectra in the insulating phase and may drive the metal-insulator transition.

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Photoemission study of hydrogen adsorption on vanadium dioxide near the semiconductor-metal phase transition

Cited by 34 publications

References 18 publications

Thermally Stable Solution Processed Vanadium Oxide as a Hole Extraction Layer in Organic Solar Cells

Thermally Stable Solution Processed Vanadium Oxide as a Hole Extraction Layer in Organic Solar Cells

Water adsorption on vanadium oxide thin films in ambient relative humidity

Temperature-Dependent Electronic Structure of VO₂in the Insulating Phase

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Photoemission study of hydrogen adsorption on vanadium dioxide near the semiconductor-metal phase transition

Cited by 34 publications

References 18 publications

Thermally Stable Solution Processed Vanadium Oxide as a Hole Extraction Layer in Organic Solar Cells

Thermally Stable Solution Processed Vanadium Oxide as a Hole Extraction Layer in Organic Solar Cells

Water adsorption on vanadium oxide thin films in ambient relative humidity

Temperature-Dependent Electronic Structure of VO2in the Insulating Phase

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Temperature-Dependent Electronic Structure of VO₂in the Insulating Phase