Electromechanical Actuation and Current-Induced Metastable States in Suspended Single-Crystalline VO2 Nanoplatelets
A. Tselev,1 J. D. Budai,2 E. Strelcov,3 J. Z. Tischler,2 A. Kolmakov3, and S. V. Kalinin1
1-Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831
2-Materials Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831
3-Physics Department, Southern Illinois University Carbondale, Carbondale, IL 62901
A novel electro-mechanical actuation principle, which can be employed at the nanometer length scale, has been demonstrated. The principle is based on reversible coupled metal-insulator and structural transitions in vanadium dioxide nanowires and nanoplatelets. It was shown that the large difference in the lattice parameters of metal and semiconductor phases of VO2 can be employed to generate electrically controlled mechanical motion. The novel concept ultimately employs coupling of both electronic and structural aspects in VO2 to achieve actuator action, in contrast to previous reports where only the thermally activated structural component of the transition was used. We find that with similar device sizes, achievable displacements are comparable to those of existing electrothermal actuator designs. The actuation can be realized over a wide temperature range, including room temperature.
Development and manufacture of functional nanoscale devices and systems ranging from smart dust sensors to nanoscale robots requires a technology for generating and controlling mechanical motion at the nanoscale. Although devices such as computer processors can effectively handle electrical signals at length scales of 10 nanometers, achieving motion at the nanoscale has remained elusive. In this work, a new strategy for generation of mechanical displacements on the nanoscale has been demonstrated. The approach uses coupling between metal-insulator and structural phase transformations in VO2 and employs the interplay between current flow, Joule heating, and phase transformations accompanied by mechanical motion. Experiments with prototypical actuator devices fabricated with single-crystalline VO2 nanoplatelets showed that the actuators based on this new electro-mechanical actuation principle can provide displacements comparable to those of existing electrothermal actuator designs of similar dimensions at operational temperatures well below 100°C, including room temperature.
This work was published online in Nano Letters, DOI: 10.1021/nl200493k. This research was conducted at the Center for Nanophase Materials Sciences, which is sponsored at Oak Ridge National Laboratory by the Office of Basic Energy Sciences, U.S. Department of Energy. JDB and JZT were supported by the Division of Materials Sciences and Engineering, Office of Basic Energy Sciences, U.S. DOE under ERKCS73 (X-ray and Neutron scattering and Microscopy). Use of the APS beamline 34-IDE was supported by the Scientific User Facilities Division of BES, U.S. DOE. The research at SIUC was supported through NSF ECCS-0925837 and SISGR-DOE ERKCM67.