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Bi2(Se(x)Te(1-x))3 纳米带和纳米片中的弱各向异性局域化。

Weak antilocalization in Bi2(Se(x)Te(1-x))3 nanoribbons and nanoplates.

机构信息

Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, USA.

出版信息

Nano Lett. 2012 Feb 8;12(2):1107-11. doi: 10.1021/nl300018j. Epub 2012 Jan 25.

Abstract

Studying the surface states of Bi(2)Se(3) and Bi(2)Te(3) topological insulators has proven challenging due to the high bulk carrier density that masks the surface states. Ternary compound Bi(2)(Se(x)Te(1-x))(3) may present a solution to the current materials challenge by lowering the bulk carrier mobility significantly. Here, we synthesized Bi(2)(Se(x)Te(1-x))(3) nanoribbons and nanoplates via vapor-liquid-solid and vapor-solid growth methods where the atomic ratio x was controlled by the molecular ratio of Bi(2)Se(3) to Bi(2)Te(3) in the source mixture and ranged between 0 and 1. For the whole range of x, the ternary nanostructures are single crystalline without phase segregation, and their carrier densities decrease with x. However, the lowest electron density is still high (10(19) cm(-3)) and the mobility low, suggesting that the majority of these carriers may come from impurity states. Despite the high carrier density, weak antilocalization (WAL) is clearly observed. Angle-dependent magnetoconductance study shows that an appropriate magnetic field range is critical to capture a true, two-dimensional (2D) WAL effect, and a fit to the 2D localization theory gives α of -0.97, suggesting its origin may be the topological surface states. The power law dependence of the dephasing length on temperature is ~T(-0.49) within the appropriate field range (0.3 T), again reflecting the 2D nature of the WAL. Careful analysis on WAL shows how the surface states and the bulk/impurity states may interact with each other.

摘要

研究 Bi(2)Se(3) 和 Bi(2)Te(3) 拓扑绝缘体的表面态极具挑战性,因为体载流子密度高会掩盖表面态。三元化合物 Bi(2)(Se(x)Te(1-x))(3) 通过显著降低体载流子迁移率,可能为当前材料挑战提供解决方案。在这里,我们通过气-液-固和汽-固生长方法合成了 Bi(2)(Se(x)Te(1-x))(3) 纳米带和纳米板,其中 x 的原子比通过源混合物中 Bi(2)Se(3)与 Bi(2)Te(3) 的分子比控制,范围在 0 到 1 之间。对于整个 x 范围,三元纳米结构都是单晶的,没有相分离,其载流子密度随 x 减小。然而,最低电子密度仍然很高(10(19) cm(-3)),迁移率低,表明这些载流子主要来自杂质态。尽管载流子密度高,但仍能明显观察到弱反局域化(WAL)。角度相关磁导研究表明,适当的磁场范围对于捕获真实的二维(2D)WAL 效应至关重要,对 2D 局域化理论的拟合给出了α=-0.97,表明其起源可能是拓扑表面态。在适当的磁场范围内(0.3 T),相位退相干长度随温度的幂律依赖关系约为~T(-0.49),再次反映了 WAL 的 2D 性质。对 WAL 的仔细分析显示了表面态和体/杂质态如何相互作用。

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