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Ambipolar field effect in the ternary topological insulator (BixSb1–x)2Te3 by composition tuning


Topological insulators exhibit a bulk energy gap and spin-polarized surface states that lead to unique electronic properties1,2,3,4,5,6,7,8,9, with potential applications in spintronics and quantum information processing. However, transport measurements have typically been dominated by residual bulk charge carriers originating from crystal defects or environmental doping10,11,12, and these mask the contribution of surface carriers to charge transport in these materials. Controlling bulk carriers in current topological insulator materials, such as the binary sesquichalcogenides Bi2Te3, Sb2Te3 and Bi2Se3, has been explored extensively by means of material doping8,9,11 and electrical gating13,14,15,16, but limited progress has been made to achieve nanostructures with low bulk conductivity for electronic device applications. Here we demonstrate that the ternary sesquichalcogenide (BixSb1–x)2Te3 is a tunable topological insulator system. By tuning the ratio of bismuth to antimony, we are able to reduce the bulk carrier density by over two orders of magnitude, while maintaining the topological insulator properties. As a result, we observe a clear ambipolar gating effect in (BixSb1–x)2Te3 nanoplate field-effect transistor devices, similar to that observed in graphene field-effect transistor devices17. The manipulation of carrier type and density in topological insulator nanostructures demonstrated here paves the way for the implementation of topological insulators in nanoelectronics and spintronics.

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Figure 1: (BixSb1–x)2Te3, a tunable topological insulator system with a single Dirac cone of surface states.
Figure 2: Characterization of (BixSb1–x)2Te3 nanoplates.
Figure 3: Ambipolar field effect in ultrathin nanoplates of (BixSb1–x)2Te3.
Figure 4: Temperature-dependent field effect in (BixSb1–x)2Te3 nanoplates.

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Y.C. acknowledges support from the Keck Foundation, a DARPA MESO project (no. N66001-11-1-4105) and a King Abdullah University of Science and Technology (KAUST) Investigator Award (no. KUS-l1-001-12). Y.L.C. acknowledges support from a DARPA MESO project (no. N66001-11-1-4105). Z.K.L., Z.X.S., Y.L.C., J.G.A. and I.R.F. acknowledge support from Department of Energy, Office of Basic Energy Science (contract DE-AC02-76SF00515). K.L. acknowledges support from the KAUST Postdoctoral Fellowship (no. KUS-F1-033-02).

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D.K., Y.L.C. and Y.C. conceived the experiments. Y.L.C. and Z.K.L. carried out ARPES measurements. J.G.A. synthesized and characterized bulk single crystals. Q.F.Z. performed electronic structure calculations. D.K. and J.J.C. carried out synthesis, structural characterization and device fabrication for nanoplates. D.K., K.L., J.J.C., S.S.H. and K.J.K. carried out transport measurements and analyses. All authors contributed to the scientific planning and discussions.

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Correspondence to Yi Cui.

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Kong, D., Chen, Y., Cha, J. et al. Ambipolar field effect in the ternary topological insulator (BixSb1–x)2Te3 by composition tuning. Nature Nanotech 6, 705–709 (2011).

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