Center of Electron Microscopy and State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, China.
Nano Lett. 2013 Jun 12;13(6):2851-6. doi: 10.1021/nl401186d.
We present a direct atom-by-atom chemical identification of the nanostructures and defects of topological insulators (TIs) with a state-of-the-art atomic mapping technology. Combining this technique and density function theory calculations, we identify and explain the layer chemistry evolution of Bi(2)Te(3–x)Se(x) ternary TIs. We also reveal a long neglected but crucially important extended defect found to be universally present in Bi(2)Te(3) films, the seven-layer Bi(3)Te(4) nanolamella acceptors. Intriguingly, this defect is found to locally pull down the conduction band, leading to local n-type conductivity, despite being an acceptor which pins the Fermi energy near the valence band maximum. This nanolamella may explain inconsistencies in measured conduction type as well as open up a new route to manipulate bulk carrier concentration. Our work may pave the way to more thoroughly understand and tailor the nature of the bulk, as well as secure controllable bulk states for future applications in quantum computing and dissipationless devices.
我们利用最先进的原子映射技术，实现了对拓扑绝缘体（TI）纳米结构和缺陷的直接原子级化学识别。结合该技术和密度泛函理论计算，我们确定并解释了 Bi(2)Te(3–x)Se(x)三元 TI 的层化学演化。我们还揭示了一个长期被忽视但至关重要的扩展缺陷，该缺陷普遍存在于 Bi(2)Te(3)薄膜中，是七层 Bi(3)Te(4)纳米薄片受主。有趣的是，尽管该缺陷是受主，会将费米能级钉扎在价带顶附近，但它被发现会局部下拉导带，导致局部 n 型导电性。这种纳米薄片可能解释了测量得到的传导类型的不一致性，并为操纵体相载流子浓度开辟了新途径。我们的工作可能为更深入地理解和调整体相的性质铺平道路，并为未来在量子计算和无损耗器件中的应用提供可控的体相状态。
