Izadi Sepideh, Han Jeong Woo, Salloum Sarah, Wolff Ulrike, Schnatmann Lauritz, Asaithambi Aswin, Matschy Sebastian, Schlörb Heike, Reith Heiko, Perez Nicolas, Nielsch Kornelius, Schulz Stephan, Mittendorff Martin, Schierning Gabi
Bielefeld University, Faculty of Physics, Experimental Physics, 33615, Bielefeld, Germany.
Leibniz IFW Dresden, Institute for Metallic Materials, 01069, Dresden, Germany.
Small. 2021 Oct;17(42):e2103281. doi: 10.1002/smll.202103281. Epub 2021 Sep 21.
3D topological insulators (TI) host surface carriers with extremely high mobility. However, their transport properties are typically dominated by bulk carriers that outnumber the surface carriers by orders of magnitude. A strategy is herein presented to overcome the problem of bulk carrier domination by using 3D TI nanoparticles, which are compacted by hot pressing to macroscopic nanograined bulk samples. Bi Te nanoparticles well known for their excellent thermoelectric and 3D TI properties serve as the model system. As key enabler for this approach, a specific synthesis is applied that creates nanoparticles with a low level of impurities and surface contamination. The compacted nanograined bulk contains a high number of interfaces and grain boundaries. Here it is shown that these samples exhibit metallic-like electrical transport properties and a distinct weak antilocalization. A downward trend in the electrical resistivity at temperatures below 5 K is attributed to an increase in the coherence length by applying the Hikami-Larkin-Nagaoka model. THz time-domain spectroscopy reveals a dominance of the surface transport at low frequencies with a mobility of above 10 cm V s even at room temperature. These findings clearly demonstrate that nanograined bulk Bi Te features surface carrier properties that are of importance for technical applications.
三维拓扑绝缘体（TI）具有极高迁移率的表面载流子。然而，它们的输运特性通常由体载流子主导，体载流子的数量比表面载流子多几个数量级。本文提出了一种策略，通过使用三维TI纳米颗粒来克服体载流子主导的问题，这些纳米颗粒通过热压被压实成宏观纳米晶块体样品。以其优异的热电和三维TI特性而闻名的Bi₂Te₃纳米颗粒用作模型系统。作为这种方法的关键促成因素，采用了一种特定的合成方法，该方法能制备出杂质和表面污染水平较低的纳米颗粒。压实后的纳米晶块体包含大量的界面和晶界。本文表明，这些样品表现出类金属的电输运特性和明显的弱反局域化。在低于5K的温度下，电阻率呈下降趋势，这归因于应用日高-拉金-长冈模型后相干长度的增加。太赫兹时域光谱显示，即使在室温下，低频时表面输运也占主导地位，迁移率高于10 cm² V⁻¹ s⁻¹。这些发现清楚地表明，纳米晶块体Bi₂Te₃具有对技术应用很重要的表面载流子特性。
