Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, USA.
Nat Nanotechnol. 2011 Oct 2;6(11):705-9. doi: 10.1038/nnano.2011.172.
Topological insulators exhibit a bulk energy gap and spin-polarized surface states that lead to unique electronic properties, 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 doping, 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 doping and electrical gating, but limited progress has been made to achieve nanostructures with low bulk conductivity for electronic device applications. Here we demonstrate that the ternary sesquichalcogenide (Bi(x)Sb(1-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 (Bi(x)Sb(1-x))2Te3 nanoplate field-effect transistor devices, similar to that observed in graphene field-effect transistor devices. 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.
拓扑绝缘体表现出体能隙和自旋极化的表面态，从而具有独特的电子性质，有望在自旋电子学和量子信息处理中得到应用。然而，传输测量通常受到晶体缺陷或环境掺杂引起的残余体电荷载流子的主导，这些电荷载流子掩盖了表面载流子对这些材料中电荷输运的贡献。通过材料掺杂和电门控，已经广泛探索了控制当前拓扑绝缘体材料（如二元硒碲化物 Bi2Te3、Sb2Te3 和 Bi2Se3）中的体载流子，但在实现具有低体电导率的纳米结构以用于电子器件应用方面，进展有限。在这里，我们证明了三元硒碲化物 (Bi(x)Sb(1-x))2Te3 是一个可调谐的拓扑绝缘体系统。通过调整铋与锑的比例，我们能够将体载流子密度降低两个数量级以上，同时保持拓扑绝缘体的特性。因此，我们在 (Bi(x)Sb(1-x))2Te3 纳米板场效应晶体管器件中观察到了明显的双极性门控效应，类似于在石墨烯场效应晶体管器件中观察到的效应。这里演示的拓扑绝缘体纳米结构中载流子类型和密度的操纵为拓扑绝缘体在纳米电子学和自旋电子学中的应用铺平了道路。
