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Title: X-ray Absorption Spectroscopy of Vanadium Dioxide Thin Films Across the Phase-Transition Boundary

Abstract

X-ray absorption spectroscopy (XAS) and x-ray photoemission spectroscopy of the V L edge and O K edge were performed on VO{sub 2} thin films rf sputtered at various conditions. The spectra give evidence of the changes in the electronic structure depending on the film quality. XAS of the O K edge shows a decrease of the spacing between 3d{sub {pi}} and 3d{sub {sigma}} bands by 0.8 eV with concurrent broadening of both bands for the sample sputtered at lower substrate temperature and consequently having more polycrystalline and disordered character. 3d{sub {sigma}} band position appears to be more sensitive to the sample quality, indicating that the cation-ligand interaction is mostly affected likely due to the distortion of the local O coordination surrounding a V ion. The observed variation of the spectra in films of different morphologies may reflect the changes of the density of states responsible for the considerable variation of the metal-insulator transition (MIT) properties reported for VO{sub 2} thin films synthesized at different conditions. The study of the temperature dependence of the XAS spectra including repeated measurements across the MIT revealed both reversible and irreversible V L-edge and O K-edge changes. The thermal cycling of the VO{sub 2} filmsmore » through the MIT shows irreversible shifts of the conduction bands toward lower photon energies apparently caused by the sample deterioration due to the lattice transformations at the MIT. The signature of a phase transition in a VO{sub 2} film at MIT temperature (T{sub MIT}) is clearly seen in the XAS O K-edge spectra which show reversible switches of the 3d{sub {pi}} and 3d{sub {sigma}} bandwidths by approximately 20% depending on the sample being above or below T{sub MIT}.« less

Authors:
; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
930664
Report Number(s):
BNL-81159-2008-JA
Journal ID: ISSN 0163-1829; PRBMDO; TRN: US0900016
DOE Contract Number:  
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review B: Condensed Matter and Materials Physics; Journal Volume: 75; Journal Issue: 19
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ABSORPTION SPECTROSCOPY; ELECTRONIC STRUCTURE; PHOTOEMISSION; PHOTONS; SPECTRA; SPECTROSCOPY; SUBSTRATES; SWITCHES; TEMPERATURE DEPENDENCE; THERMAL CYCLING; THIN FILMS; TRANSFORMATIONS; VANADIUM; national synchrotron light source

Citation Formats

Ruzmetov,D., Senanayake, S., and Ramanathan, S. X-ray Absorption Spectroscopy of Vanadium Dioxide Thin Films Across the Phase-Transition Boundary. United States: N. p., 2007. Web. doi:10.1103/PhysRevB.75.195102.
Ruzmetov,D., Senanayake, S., & Ramanathan, S. X-ray Absorption Spectroscopy of Vanadium Dioxide Thin Films Across the Phase-Transition Boundary. United States. doi:10.1103/PhysRevB.75.195102.
Ruzmetov,D., Senanayake, S., and Ramanathan, S. Mon . "X-ray Absorption Spectroscopy of Vanadium Dioxide Thin Films Across the Phase-Transition Boundary". United States. doi:10.1103/PhysRevB.75.195102.
@article{osti_930664,
title = {X-ray Absorption Spectroscopy of Vanadium Dioxide Thin Films Across the Phase-Transition Boundary},
author = {Ruzmetov,D. and Senanayake, S. and Ramanathan, S.},
abstractNote = {X-ray absorption spectroscopy (XAS) and x-ray photoemission spectroscopy of the V L edge and O K edge were performed on VO{sub 2} thin films rf sputtered at various conditions. The spectra give evidence of the changes in the electronic structure depending on the film quality. XAS of the O K edge shows a decrease of the spacing between 3d{sub {pi}} and 3d{sub {sigma}} bands by 0.8 eV with concurrent broadening of both bands for the sample sputtered at lower substrate temperature and consequently having more polycrystalline and disordered character. 3d{sub {sigma}} band position appears to be more sensitive to the sample quality, indicating that the cation-ligand interaction is mostly affected likely due to the distortion of the local O coordination surrounding a V ion. The observed variation of the spectra in films of different morphologies may reflect the changes of the density of states responsible for the considerable variation of the metal-insulator transition (MIT) properties reported for VO{sub 2} thin films synthesized at different conditions. The study of the temperature dependence of the XAS spectra including repeated measurements across the MIT revealed both reversible and irreversible V L-edge and O K-edge changes. The thermal cycling of the VO{sub 2} films through the MIT shows irreversible shifts of the conduction bands toward lower photon energies apparently caused by the sample deterioration due to the lattice transformations at the MIT. The signature of a phase transition in a VO{sub 2} film at MIT temperature (T{sub MIT}) is clearly seen in the XAS O K-edge spectra which show reversible switches of the 3d{sub {pi}} and 3d{sub {sigma}} bandwidths by approximately 20% depending on the sample being above or below T{sub MIT}.},
doi = {10.1103/PhysRevB.75.195102},
journal = {Physical Review B: Condensed Matter and Materials Physics},
number = 19,
volume = 75,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}