Ambipolar Surface Conduction in Ternary Topological Insulator Bi2(Te1–xSex)3 Nanoribbons

Abstract
We report the composition- and gate voltage-induced tuning of transport properties in chemically synthesized Bi2(Te1–xSex)3 nanoribbons. It is found that increasing Se concentration effectively suppresses the bulk carrier transport and induces semiconducting behavior in the temperature-dependent resistance of Bi2(Te1–xSex)3 nanoribbons when x is greater than ∼10%. In Bi2(Te1–xSex)3 nanoribbons with x ≈ 20%, gate voltage enables ambipolar modulation of resistance (or conductance) in samples with thicknesses around or larger than 100 nm, indicating significantly enhanced contribution in transport from the gapless surface states.
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