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arXiv 1707.01752cond-mat.mtrl-sci
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SbAs中晶格热导率低于As或Sb单层的第一性原理研究

Lower lattice thermal conductivity in SbAs than As or Sb monolayer: a first-principles study

San-Dong Guo

摘要:

VA族元素(As,Sb,Bi)单层半导体的声子输运在理论上得到了广泛的研究,其中Sb单层半导体(锑烯)的合成是近年来研究的热点。利用第一性原理计算和线性化的声子Boltzmann方程研究了SbAs单分子膜的声子输运。结果表明,SbAs单层的晶格热导率低于As和Sb单层,室温下对应的薄层热导率为28.8 $\mathrm{W K^{-1}}$.计算结果表明,SbAs单分子膜的群速度介于As和Sb单分子膜的群速度之间,但SbAs的声子寿命小于As和Sb单分子膜的声子寿命。因此,低的晶格热导率在SbAs单层归因于非常小的声子寿命。出乎意料的是,ZA支对总热导率的贡献很小,仅为2.4%,这与贡献很大的As和Sb单分子膜明显不同。这可以解释为非常小的声子寿命为ZA分支的SbAs单层。Sb原子向As原子的大量电荷转移导致了强极化的共价键,这与As或Sb单层膜不同。SbAs单层膜的强极化共价键可以诱导比As或Sb单层膜更强的声子非简谐性,导致更低的晶格热导率。结果表明,同位素散射对晶格热导率的影响很小,当特征长度小于30 nm时,晶格热导率可降低约47%.这些结果可能提供的观点,通过多元素的混合物调节晶格热导率的热管理和热电的应用,并激励进一步的实验努力,以合成单层SbAs。

英文摘要:

Phonon transports of group-VA elements (As, Sb, Bi) monolayer semiconductors have been widely investigated in theory, and Sb monolayer (antimonene) of them has recently been synthesized. In this work, phonon transport of SbAs monolayer is investigated from a combination of first-principles calculations and the linearized phonon Boltzmann equation. It is found that the lattice thermal conductivity of SbAs monolayer is lower than ones of both As and Sb monolayers, and the corresponding sheet thermal conductance is 28.8 $\mathrm{W K^{-1}}$ at room temperature. Calculated results show that group velocities of SbAs monolayer are between ones of As and Sb onolayers, but phonon lifetimes of SbAs are smaller than ones of both As and Sb monolayers. Hence, low lattice thermal conductivity in SbAs monolayer is attributed to very small phonon lifetimes. Unexpectedly, the ZA branch has very little contribution to the total thermal conductivity, only 2.4\%, which is obviously different from ones of As and Sb monolayers with very large contribution. This can be explained by very small phonon lifetimes for ZA branch of SbAs monolayer. The large charge transfer from Sb to As atoms leads strongly polarized covalent bond, being different from As or Sb monolayer. The strongly polarized covalent bond of SbAs monolayer can induce stronger phonon anharmonicity than As or Sb monolayer, leading to lower lattice thermal conductivity. It is found that isotope scattering produces neglectful effect, and the lattice thermal conductivity with the characteristic length smaller than 30 nm can reach a decrease of about 47\%. These results may offer perspectives on tuning lattice thermal conductivity by mixture of multi-elements for applications of thermal management and thermoelectricity, and motivate further experimental efforts to synthesize monolayer SbAs.

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