VO2 nanosheets exhibiting a well-defined metal-insulator phase transition
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abstract
The ultrafast first-order metal-insulator phase transition in VO 2 is characterized by a several orders of magnitude change in optical transmittance and electrical conductivity, which makes this material an attractive candidate for use in a wide variety of applications ranging from Mott field-effect transistors to thermochromic coatings and optical waveguides. However, relatively little progress has been achieved in fabricating VO 2 nanostructures exhibiting a well-defined metal-insulator transition despite the potential attractiveness of such structures as building blocks for novel nanoscale electronic devices. Herein, we present a solution-based approach for the synthesis of monoclinic single-crystalline VO 2 nanosheets exhibiting a well-defined metal-insulator phase transition by combining the facile hydrothermal reduction of V 2O 5, an inexpensive and abundant precursor, with an annealing process. The controlled hydrothermal reduction of bulk V 2O 5 using small molecule aliphatic alcohols and ketones as reducing agents yields metastable nanostructures of VO 2(B) that can be readily transformed to monoclinic VO 2 exhibiting a sharp metal-insulator phase transition via an annealing process. The morphology and size of the obtained VO 2 nanostructures are found to depend on the reaction time and concentration of the added structure-directing agent, providing substantial insight into the nanowire formation process. 2009 The Royal Society of Chemistry.
