Topological insulator Bi$_{2}$Te$_{3}$ nanowire field effect devices

Bismuth telluride (Bi$_{2}$Te$_{3})$ has been studied extensively as one of the best thermoelectric materials and recently shown to be a prototype topological insulator with nontrivial conducting surface states. We have grown Bi$_{2}$Te$_{3}$ nanowires by a two-step solution phase reaction and characterized their material and structural properties by XRD, TEM, XPS and EDS. We fabricate both backgated (on SiO$_{2}$/Si) and top-gated (with ALD high-k gate dielectric such as Al$_{2}$O$_{3}$ or HfO$_{2})$ field effect devices on such nanowires with diameters $\sim $50nm. Ambipolar field effect and a resistance modulation of up to 600{\%} at low temperatures have been observed. The 4-terminal resistance shows insulating behavior (increasing with decreasing temperature) from 300~K to 50K, then saturates in a plateau for temperatures below 50K, consistent with the presence of metallic surface state. Aharonov--Bohm (AB) oscillations are observed in the magneto-resistance with a magnetic field parallel to the nanowire, providing further evidence of the presence of surface state conduction Finally, a prominent weak anti-localization (WAL) feature that weakens with increasing magnetic field and/or temperature is observed in the magneto-resistance with a magnetic field perpendicular to the nanowire.