Strain-induced phase transformation and piezoresistivity in VO 2 nanowires
- PDF / 852,456 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 28 Downloads / 194 Views
esearch Letters
Strain-induced phase transformation and piezoresistivity in VO2 nanowires A. Sedlmayr, R. Mönig, S.T. Boles, G. Kilibarda, and O. Kraft, Institute for Applied Materials, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany Address all correspondence to R. Mönig at [email protected] (Received 25 January 2012; accepted 14 March 2012)
Abstract We report on the mechanical and electrical response of VO2 nanowires during the application of uniaxial tensile strain at room temperature. Stress–strain curves exhibit plateaus, which are characteristic of reversible transformations. The mechanical data are also discussed in terms of size effects, which is important for applications where the structural integrity is key to the performance of devices. Electrical measurements during straining show a distinct increase in resistivity at the M1–M2 transition, and a strong piezo-resistive effect for the M2 phase, disclosing new opportunities for future nanostructured devices. To our knowledge, this is the first time that piezoresistivity in the M2 phase has been reported.
Many applications for transition metal oxides, and particularly for VO2, have been proposed. Among them are field effect transistors,[1] energy-efficient window coatings[2,3] and gas sensors.[4] However, to extend the field of applications, a deeper fundamental understanding of the occurring phase transformations and the related mechanical and electronic properties of VO2 is required. Pure strain-free VO2 is subjected to a phase transformation at 341 K from the high-temperature tetragonal metallic R phase to the monoclinic insulating M1 phase, accompanied by a change in resistance of several orders of magnitude.[5–7] The presence of an additional insulating M2 phase has been determined to appear under uniaxial stress or from doping of VO2.[6,8–10] Pouget et al.[11] demonstrated that the M2 phase could be stabilized by uniaxial stress and postulate this metastable M2 phase to be a Mott insulator, where electronic properties are significantly influenced by external forces. For the understanding and the application of correlated electron materials (CEM), the electrical response to temperature and mechanical load is important. In particular, the coupling between the mechanical load, phase transformations and electronic properties can be difficult to determine in bulk materials. Recently, the synthesis of nanoscale one-dimensional singlecrystalline structures strongly improved the opportunities to investigate and understand CEMs. When these are produced without preexisting defects, they can be subjected to extreme mechanical stresses without fracture, considerably exceeding the strengths of their bulk counterparts.[12–15] Most investigations to date have addressed the metal–insulator phase transition between M1 and R.[12,13] Only little work has been done on investigating the insulator–insulator transition between M1 and M2 and characterizing M2.
However, the recent fabrication of nanostructured single crystals has spurred the detaile
Data Loading...
