Growth control of the oxidation state in vanadium oxide thin films

Abstract

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 V2(+3)O3, V(+4)O2, and V2(+5)O5. A well pronounced MIT was only observed in VO2 films grown in a very narrow range of oxygen partial pressure P(O2). The films grown either in lower (< 10 mTorr) or higher P(O2) (> 25 mTorr) result in V2O3 and V2O5 phases, respectively, thereby suppressing the MIT for both cases. We have also found that the resistivity ratio before and after the MIT of VO2 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.

arXiv comment16 pages, 4 figures

References in corpus (9)

• Mott transition in VO2 revealed by infrared spectroscopy and nano-imaging
• Memory Metamaterials
• Electrodynamics of Correlated Electron Materials
• Reversible redox reactions in an epitaxially stabilized SrCoOx oxygen sponge
• Half-metallic semiDirac point generated by quantum confinement in TiO${}_2$/VO${}_2$ nanostructures
• Strongly Correlated Materials
• A Microscopic View on the Mott transition in Chromium-doped V2O3
• Reversal of the lattice structure in SrCoOx epitaxial thin films studied by real-time optical spectroscopy and first-principles calculations
• Atomic layer engineering of perovskite oxides for chemically sharp heterointerfaces

Cited by in corpus (4)

• Enhanced passive thermal stealth properties of VO${}_2$ thin films via gradient W doping
• Structural evolution of epitaxial SrCoOx films near topotactic phase transition
• Reversible modulation of metal-insulator transition in VO2 via chemically-induced oxygen migration
• Maximizing Infrared Transmission Contrast Upon Phase Transition of Thermally Grown Vanadium Dioxide Thin Films by Rapid Thermal Processing