Ultrathin Films of VO2 on r-Cut Sapphire Achieved by Postdeposition Etching

Tony Yamin, Shai Wissberg, Hagai Cohen, Gili Cohen-Taguri, Amos Sharoni

Research output: Contribution to journalArticlepeer-review

19 Scopus citations

Abstract

The metal-insulator transition (MIT) properties of correlated oxides thin films, such as VO2, are dramatically affected by strain induced at the interface with the substrate, which usually changes with deposition thickness. For VO2 grown on r-cut sapphire, there is a minimum deposition thickness required for a significant MIT to appear, around 60 nm. We show that in these thicker films an interface layer develops, which accompanies the relaxation of film strain and enhanced electronic transition. If these interface dislocations are stable at room temperature, we conjectured, a new route opens to control thickness of VO2 films by postdeposition thinning of relaxed films, overcoming the need for thickness-dependent strain-engineered substrates. This is possible only if thinning does not alter the films' electronic properties. We find that wet etching in a dilute NaOH solution can effectively thin the VO2 films, which continue to show a significant MIT, even when etched to 10 nm, for which directly deposited films show nearly no transition. The structural and chemical composition were not modified by the etching, but the grain size and film roughness were, which modified the hysteresis width and magnitude of the MIT resistance change.

Original languageEnglish
Pages (from-to)14863-14870
Number of pages8
JournalACS applied materials & interfaces
Volume8
Issue number23
DOIs
StatePublished - 15 Jun 2016

Bibliographical note

Publisher Copyright:
© 2016 American Chemical Society.

Keywords

  • VO
  • oxide electronics
  • strain engineering
  • thinning
  • ultrathin

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