Light-induced ultrafast phase transitions in VO 2 thin film

S. Lysenko, A. J. Rua, V. Vikhnin, J. Jimenez, F. Fernandez, H. Liu

Research output: Contribution to journalArticle

85 Scopus citations

Abstract

Vanadium dioxide shows a passive and reversible change from a monoclinic insulator phase to a metallic tetragonal rutile structure when the sample temperature is close to and over 68 °C. As a kind of functional material, VO 2 thin films deposited on fused quartz substrates were successfully prepared by the pulsed laser deposition (PLD) technique. With laser illumination at 400 nm on the obtained films, the phase transition (PT) occurred. The observed light-induced PT was as fast as the laser pulse duration of 100 fs. Using a femtosecond laser system, the relaxation processes in VO 2 were studied by optical pump-probe spectroscopy. Upon a laser excitation an instantaneous response in the transient reflectivity and transmission was observed followed by a relatively longer relaxation process. The alteration is dependent on pump power. The change in reflectance reached a maximum value at a pump pulse energy between 7 and 14 mJ/cm 2 . The observed PT is associated with the optical interband transition in VO 2 thin film. It suggests that with a pump laser illuminating on the film, excitation from the d θ,ε - state of valence band to the unoccupied excited mixed d θ,ε -π* - state of the conduction band in the insulator phase occurs, followed by a resonant transition to an unoccupied excited mixed d θ,ε -π* - state of the metallic phase band.

Original languageEnglish (US)
Pages (from-to)5512-5515
Number of pages4
JournalApplied Surface Science
Volume252
Issue number15
DOIs
Publication statusPublished - May 30 2006
Externally publishedYes

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Keywords

  • Exciton
  • Laser excitation
  • Phase transition
  • Thin film
  • Ultrafast
  • VO

ASJC Scopus subject areas

  • Chemistry(all)
  • Condensed Matter Physics
  • Physics and Astronomy(all)
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films

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