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Title: Growth control of the oxidation state in vanadium oxide thin films

Precise control of the chemical valence or oxidation state of vanadium in vanadium oxide thin films is highly desirable for not only fundamental research but also technological applications that utilize the subtle change in the physical properties originating from the metal-insulator transition (MIT) near room temperature. However, due to the multivalent nature of vanadium and the lack of a good understanding on growth control of the oxidation state, stabilization of phase pure vanadium oxides with a single oxidation state is extremely challenging. Here, we systematically varied the growth conditions to clearly map out the growth window for preparing phase pure epitaxial vanadium oxides by pulsed laser deposition for providing a guideline to grow high quality thin films with well-defined oxidation states of V{sub 2}{sup +3}O{sub 3}, V{sup +4}O{sub 2}, and V{sub 2}{sup +5}O{sub 5}. A well pronounced MIT was only observed in VO{sub 2} films grown in a very narrow range of oxygen partial pressure P(O{sub 2}). The films grown either in lower (<10 mTorr) or higher P(O{sub 2}) (>25 mTorr) result in V{sub 2}O{sub 3} and V{sub 2}O{sub 5} phases, respectively, thereby suppressing the MIT for both cases. We have also found that the resistivity ratio before and aftermore » the MIT of VO{sub 2} thin films can be further enhanced by one order of magnitude when the films are further oxidized by post-annealing at a well-controlled oxidizing ambient. This result indicates that stabilizing vanadium into a single valence state has to compromise with insufficient oxidation of an as grown thin film and, thereby, a subsequent oxidation is required for an improved MIT behavior.« less
Authors:
; ;  [1] ;  [1] ;  [2] ;  [1] ;  [3] ;  [3]
  1. Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)
  2. (Korea, Republic of)
  3. (United States)
Publication Date:
OSTI Identifier:
22402442
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 105; Journal Issue: 22; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ANNEALING; ENERGY BEAM DEPOSITION; EPITAXY; LASER RADIATION; OXIDATION; PARTIAL PRESSURE; PULSED IRRADIATION; TEMPERATURE RANGE 0273-0400 K; THIN FILMS; VALENCE; VANADIUM; VANADIUM IONS; VANADIUM OXIDES