Srivastava Punita, Kumar Pushpendra, Singh Kedar
J Nanosci Nanotechnol. 2014 Aug;14(8):5856-63. doi: 10.1166/jnn.2014.8882.
Bismuth telluride (Bi2Te3) and its associated compounds are the best bulk thermoelectric (TE) materials known in present day. In addition, stacked two-dimensional (2D) layers of Bi2Te3 have attracted brawny interest due to topologically protected surface state property. The authors herein report results of micro-Raman spectroscopy study of the "graphene-like" crystalline Bi2Te3 nanosheets with a thickness of a few atoms (few-quintuples) synthesized by convenient solvothermal route which is chiefly attractive from physics point of view. It is investigated that the optical phonon mode A1u, which is not-Raman active in bulk Bi2Te3 crystals, appears in atomically-thin nanosheets due to crystal-symmetry breaking in few quintuples layers (FQLs) and can be used in nanometrology of topological insulators (TIs). It is also suggested that sheets thinning to FQLs and tuning of Fermi level can help in achieving TI surface transport regime with enhance thermoelectric power. From seebeck measurements, Bi2Te3 sample exhibit p-type conduction having higher TE power at low temperature (40 K). Thus, Bi2Te3 nanosheets with strong spatial confinement of charge carriers are beneficial for TE devices. The developed technology for producing 2D layers of -Te(1)-Bi-Te(2)-Bi-Te(1)- creates an thrust for exploration of TIs and their possibility in practical applications.
碲化铋（Bi2Te3）及其相关化合物是当今已知的最佳体相热电（TE）材料。此外，由于拓扑保护的表面态特性，堆叠的二维（2D）Bi2Te3层引起了广泛关注。本文作者报告了通过便捷的溶剂热法合成的具有几个原子厚度（几个五重层）的“类石墨烯”晶体Bi2Te3纳米片的显微拉曼光谱研究结果，这主要从物理学角度来看很有吸引力。研究发现，在体相Bi2Te3晶体中不具有拉曼活性的光学声子模式A1u，由于在几个五重层（FQLs）中晶体对称性的破坏，出现在原子级薄的纳米片中，并且可用于拓扑绝缘体（TIs）的纳米计量学。还表明，薄片变薄至FQLs以及费米能级的调节有助于实现具有增强热电功率的TI表面传输机制。从塞贝克测量结果来看，Bi2Te3样品表现出p型传导，在低温（40 K）下具有更高的TE功率。因此，具有强电荷载流子空间限制的Bi2Te3纳米片对TE器件有益。用于生产-Te(1)-Bi-Te(2)-Bi-Te(1)-二维层的已开发技术为探索TIs及其在实际应用中的可能性创造了动力。
