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arXiv · 1604.04306

Ultrafast mid-infrared nanoscopy of strained vanadium dioxide nanobeams

M. A. Huber·M. Plankl·M. Eisele·R. E. Marvel·F. Sandner·T. Korn·C. Schüller·R. F. Haglund, Jr.·R. Huber·T. L. Cocker
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Abstract

Long regarded as a model system for studying insulator-to-metal phase transitions, the correlated electron material vanadium dioxide (VO$_2$) is now finding novel uses in device applications. Two of its most appealing aspects are its accessible transition temperature ($\sim$341 K) and its rich phase diagram. Strain can be used to selectively stabilize different VO$_2$ insulating phases by tuning the competition between electron and lattice degrees of freedom. It can even break the mesoscopic spatial symmetry of the transition, leading to a quasi-periodic ordering of insulating and metallic nanodomains. Nanostructuring of strained VO$_2$ could potentially yield unique components for future devices. However, the most spectacular property of VO$_2$ - its ultrafast transition - has not yet been studied on the length scale of its phase heterogeneity. Here, we use ultrafast near-field microscopy in the mid-infrared to study individual, strained VO$_2$ nanobeams on the 10 nm scale. We reveal a previously unseen correlation between the local steady-state switching susceptibility and the local ultrafast response to below-threshold photoexcitation. These results suggest that it may be possible to tailor the local photo-response of VO$_2$ using strain and thereby realize new types of ultrafast nano-optical devices.

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M. A. Huber, M. Plankl, M. Eisele, R. E. Marvel, F. Sandner, T. Korn, C. Schüller, R. F. Haglund, Jr., R. Huber, T. L. Cocker. 2016-04-14. Ultrafast mid-infrared nanoscopy of strained vanadium dioxide nanobeams. https://doi.org/10.1021/acs.nanolett.5b04988

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