Direct observation of vast off-stoichiometric defects in single crystalline SnSe
Direct observation of vast off-stoichiometric defects in single crystalline SnSe
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直接观察单晶 SnSe 中大量的非化学计量缺陷
DOI：
10.1016/j.nanoen.2017.04.004
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发表时间：
2017-05
期刊：
影响因子：
17.6
通讯作者：
He Jiaqing
中科院分区：
文献类型：
--
作者：
Wu Di;Wu Lijun;He Dongsheng;Zhao Li-Dong;Li Wei;Wu Minghui;Jin Min;Xu Jingtao;Jiang Jun;Huang Li;Zhu Yimei;Kanatzidis Mercouri G.;He Jiaqing
单晶硒化锡（SnSe）最近成为一种非常有前途的热电材料，用于废热收集和热电冷却，因为它具有创纪录的高品质因数ZTin适中的温度范围。 SnSe最显着的特征在于其极低的晶格热导率，这归因于先前研究中的各向异性和高度扭曲的Sn-Se键以及巨大的键非和谐性，但迄今为止还没有理论模型可以对如此低的晶格热导率给出定量解释。在这项工作中，我们使用复杂的像差校正扫描透射电子显微镜直接观察了大量的非化学计量的锡空位和硒间隙原子；并将之前报道的 SnSe 单晶样品的超低导热率部分归因于其非化学计量特征。为了进一步验证结论，我们还合成了化学计量的SnSe单晶样品，并表明与非化学计量的单晶相比，其晶格热导率确实要高得多。然后在最先进的 Debye-Callaway 模型中讨论了载热声子上单个点缺陷的散射效率。
Single crystalline tin selenide (SnSe) recently emerged as a very promising thermoelectric material for waste heat harvesting and thermoelectric cooling, due to its record high figure of meritZTin mediate temperature range. The most striking feature of SnSe lies in its extremely low lattice thermal conductivity as ascribed to the anisotropic and highly distorted Sn-Se bonds as well as the giant bond anharmonicity by previous studies, yet no theoretical models so far can give a quantitative explanation to such low a lattice thermal conductivity. In this work, we presented direct observation of an astonishingly vast number of off-stoichiometric Sn vacancies and Se interstitials, using sophisticated aberration corrected scanning transmission electron microscope; and credited the previously reported ultralow thermal conductivity of the SnSe single crystalline samples partly to their off-stoichiometric feature. To further validate the conclusion, we also synthesized stoichiometric SnSe single crystalline samples, and illustrated that the lattice thermal conductivity is deed much higher as compared with the off-stoichiometric single crystals. The scattering efficiency of individual point defect on heat-carrying phonons was then discussed in the state-of-art Debye-Callaway model.
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