接力键增强PbTe基纳米孪晶热电半导体的塑性变形 | Cell Press青促会述评

作为世界领先的全科学领域学术出版社，细胞出版社特与“中国科学院青年创新促进会”合作开设“青促会述评”专栏，以期增进学术互动，促进国际交流。

2022年第十二期（总第96期）专栏文章，由来自中国科学院化学研究所副研究员 中科院青年创新促进会会员 荆莉红，就 Matter中的论文发表述评。

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▲图1 纳米孪晶PbTe的原子构型：（A）PbTe的岩盐型完美晶体结构，沿(111)面的（B）Pb封端的共格孪晶界（Pb-CTB）以及（C）Te封端的共格孪晶界（Te-CTB）结构图

▲图2 Pb-CTB结构中破环应力与CTB数量的关系

▲图3 剪切应力下Pb-CTB迁移为Te-CTB原子构型

▲图4 Pb-CTB和Te-CTB的迁移能

具有最低相界能量的共格孪晶界(CTB)可有效增强晶界处的声子散射，进而降低晶格热导率以提升热电性能，但CTB对PbTe半导体的力学性能影响仍未得到探索。通过沿(111)晶面构建具有Pb或Te封端的CTB（Pb-或Te-CTB）的纳米孪晶结构模型，并采用分子动力学模拟了材料的结构演化规律。发现Pb-CTB会削弱Pb-Te离子键，从而利于在CTB上发生相界分离。在剪切应力下每个Pb-CTB平面滑移，使Pb-CTBs逐渐向Te-CTBs迁移，伴随着Pb-Te键的断裂和重新形成。这种“接力键”的方式保持了材料结构的完整性，同时显著提高了纳米孪晶PbTe的塑性变形能力。而Te-CTB结构易导致材料的断裂破坏。这些发现为通过孪晶界工程提高PbTe基热电半导体的塑性形变提供了新的理论策略。

Coherent twin boundaries (CTBs) with the lowest interfacial energy provide a strong phonon-CTB scattering source to suppress the lattice thermal conductivity needed for thermoelectric properties, but the impact on mechanical properties of PbTe remains unexplored. We construct nanotwinned structures with Pb- or Te-terminated CTB (Pb- or Te-CTB) along (111) plane and employ molecular dynamics simulations to examine structural evolution. We find that Pb-CTBs weaken ionic Pb-Te bonds to generate an easy dislocation source at CTBs. Due to nucleation and motion of partial dislocations on each Pb-CTB plane driven by shear load, Pb-CTBs gradually migrate to Te-CTBs, which is accompanied by breaking and re-forming of Pb-Te bonds. This ‘‘catching bond’’ maintains structural integrity while dramatically enhancing deformability of nanotwinned PbTe. Dislocations move from Te-CTBs toward twin lamellae, result-ing in the structural slippage and fracture. These findings provide a theoretical strategy to improve the ductility of PbTe-based semiconductors through TB engineering.

荆莉红，中国科学院青年创新促进会会员，中国科学院化学研究所副研究员，中国医药生物技术协会造影技术分会第一届委员会委员。主要从事量子点光电功能材料的设计合成及应用研究。第一/通讯作者论文包括Science Translational Medicine, J. Am. Chem. Soc., Adv. Mater., ACS Nano, Chem. Rev.等，发表SCI论文60余篇。2020年入选英国皇家化学学会JMCB杂志新锐研究者。2021年起担任《Nano Research》青年编委。

Lihong Jing is an associate professor in Institute of Chemistry, Chinese Academy of Sciences (ICCAS). She has been a “Member of Youth Innovation Promotion Association CAS” since 2018. Her research focuses the synthesis and applications of luminescent semiconductor quantum dots. She has published 60 papers in Science Transl. Med., J. Am. Chem. Soc., Adv. Mater., ACS Nano, Chem. Rev., etc. She was selected as one of 2020 JMCB Emerging Investigators. She has been selected as one of the young editorial board members of Nano Research.

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