Resistance modulation in VO$_{\mathrm{2}}$ nanowires induced by an electric field \textit{via} air-gap gates

Vanadium dioxide (VO$_{\mathrm{2}})$ shows huge resistance change with metal-insulator transition (MIT) at around room temperature. Controlling of the MIT by applying an electric field is a topical ongoing research toward the realization of Mott transistor. In this study, we have successfully switched channel resistance of VO$_{\mathrm{2}}$ nano-wire channels by a pure electrostatic field effect using a side-gate-type field-effect transistor (SG-FET) \textit{via }air gap and found that single crystalline VO$_{\mathrm{2}}$ nanowires and the channels with narrower width enhance transport modulation rate. The rate of change in resistance ( (R$_{\mathrm{0}}$-R)/R, where R$_{\mathrm{0}}$ and R is the resistance of VO$_{\mathrm{2}}$ channel with off state and on state gate voltage (V$_{\mathrm{G}})$, respectively) was 0.42 {\%} at V$_{\mathrm{G}}=$30 V in in-plane poly-crystalline VO$_{\mathrm{2}}$ channels on Al$_{\mathrm{2}}$O$_{\mathrm{3}}$(0001) substrates, while the rate in single crystalline channels on TiO$_{\mathrm{2}}$ (001) substrates was 3.84 {\%}, which was 9 times higher than that using the poly-crystalline channels. With reducing wire width from 3000 nm to 400 nm of VO$_{\mathrm{2}}$ on TiO$_{\mathrm{2}}$ (001) substrate, furthermore, resistance modulation ratio enhanced from 0.67 {\%} to 3.84 {\%}. This change can not be explained by a simple free-electron model. In this presentation, we will compare the electronic properties between in-plane polycrystalline VO$_{\mathrm{2}}$ on Al$_{\mathrm{2}}$O$_{\mathrm{3}}$ (0001) and single crystalline VO$_{\mathrm{2}}$ on TiO$_{\mathrm{2}}$ (001) substrates, and show experimental data in detail..