Transformation and Actuation Properties of Vanadium Dioxide-Based NanostructuresTuesday (18.06.2019) 12:15 - 12:30
We report on the electrical and mechanical properties of vanadium dioxide-(VO2-) based nanostructures with critical dimensions down to 100 nm. Vanadium dioxide VO2 is a multifunctional ceramic material that exhibits a reversible phase transformation between the tetragonal (rutile structure) and monoclinic phase, which is accompanied by abrupt changes in electrical, optical and mechanical properties. As the Young’s modulus is rather large, about 140 GPa, large forces and high work densities can be achieved. Here, our interest is in the investigation of free-standing VO2-based structures at the nanoscale, which will open up new opportunities to use the multi-functional material properties for nanoactuation and -sensing. Starting materials are VO2 films that are deposited by magnetron sputtering . Addition of third elements, e.g., molybdenum (Mo), is used to tune the phase transformation temperatures. For nanofabrication, a top-down process has been developed based on electron beam lithography and reactive ion etching. Electrical resistance measurements of V0.99Mo0.01O2-based free-standing nanobridges exhibit a semiconductor-metal transition near 60 °C and a change in electrical resistance of more than two orders of magnitude. By deposition of a thin layer of chromium (Cr) on free-standing structures, bilayer nano-actuators of Cr/VMoO2 are fabricated. The actuation properties are investigated in detail by ambient heating as well as Joule heating in-situ inside a SEM for decreasing lateral dimensions of the nanobeams.
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