School of Physics, China University of Mining and Technology, Xuzhou 221116, Jiangsu, People's Republic of China.
Nanotechnology. 2017 Nov 3;28(44):445702. doi: 10.1088/1361-6528/aa8741. Epub 2017 Aug 21.
Lots of two-dimensional (2D) materials have been predicted theoretically and further confirmed in experiments, and have wide applications in nanoscale electronic, optoelectronic and thermoelectric devices. In this work, the thermoelectric properties of ATeI (A = Sb and Bi) monolayers are systematically investigated according to semiclassical Boltzmann transport theory. It is found that spin-orbit coupling (SOC) has an important effect on the electronic transport coefficients of p-type doping, but a negative influence on n-type doping. The room-temperature sheet thermal conductance is 14.2 [Formula: see text] for SbTeI and 12.6 [Formula: see text] for BiTeI, which is lower than that of most well-known 2D materials, such as the transition-metal dichalcogenide, group IV-VI, group VA and group IV monolayers. The very low sheet thermal conductance of ATeI (A = Sb and Bi) monolayers is mainly due to their small group velocities and short phonon lifetimes. The strongly polarized covalent bonds between A and Te or I atoms induce strong phonon anharmonicity, which gives rise to low lattice thermal conductivity. It is found that the high-frequency optical branches contribute significantly to the total thermal conductivity, which is obviously different from the usual picture, where there is little contribution from the optical branches. According to cumulative lattice thermal conductivity with respect to the phonon mean free path (MFP), it is difficult to further reduce the lattice thermal conductivity using nanostructures. Finally, the possible thermoelectric figure of merit ZT values of the ATeI (A = Sb and Bi) monolayers are calculated. It is found that p-type doping has much better thermoelectric properties than n-type doping. At room temperature, the peak ZT can reach 1.11 for SbTeI and 0.87 for BiTeI, respectively. These results make us believe that ATeI (A = Sb and Bi) monolayers may be potential 2D thermoelectric materials, which could stimulate further experimental work towards the synthesis of these monolayers.
大量的二维（2D）材料已被理论预测，并在实验中进一步证实，它们在纳米尺度电子、光电和热电器件中有广泛的应用。在这项工作中，根据半经典玻尔兹曼输运理论，系统地研究了 ATelI（A = Sb 和 Bi）单层的热电性质。结果发现，自旋轨道耦合（SOC）对 p 型掺杂的电子输运系数有重要影响，但对 n 型掺杂有负面影响。室温下 SbTeI 的面热导为 14.2 [Formula: see text]，BiTeI 的面热导为 12.6 [Formula: see text]，低于大多数众所周知的 2D 材料，如过渡金属二卤化物、IV-VI 族、VA 族和 IV 族单层。ATelI（A = Sb 和 Bi）单层非常低的面热导主要是由于它们的群速度小和声子寿命短。A 与 Te 或 I 原子之间强烈极化的共价键引起强烈的声子非谐性，导致晶格热导率低。结果发现，高频光学支对总热导率有显著贡献，这与通常的情况明显不同，通常情况下，光学支的贡献很小。根据晶格热导率随声子平均自由程（MFP）的累积，利用纳米结构很难进一步降低晶格热导率。最后，计算了 ATelI（A = Sb 和 Bi）单层的可能热电优值 ZT 值。结果表明，p 型掺杂的热电性能比 n 型掺杂好得多。在室温下，SbTeI 的峰值 ZT 可达到 1.11，BiTeI 的峰值 ZT 可达到 0.87。这些结果使我们相信 ATelI（A = Sb 和 Bi）单层可能是潜在的 2D 热电材料，这可能会激发进一步的实验工作，以合成这些单层。
