Department of Physics, Zhejiang University, Hangzhou, 310027, China.
State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology (SIMIT), Chinese Academy of Sciences, Shanghai, 200050, China.
Nat Commun. 2018 Jan 3;9(1):47. doi: 10.1038/s41467-017-02566-1.
SnSe is a promising thermoelectric material with record-breaking figure of merit. However, to date a comprehensive understanding of the electronic structure and most critically, the self-hole-doping mechanism in SnSe is still absent. Here we report the highly anisotropic electronic structure of SnSe investigated by angle-resolved photoemission spectroscopy, in which a unique pudding-mould-shaped valence band with quasi-linear energy dispersion is revealed. We prove that p-type doping in SnSe is extrinsically controlled by local phase segregation of SnSe microdomains via interfacial charge transferring. The multivalley nature of the pudding-mould band is manifested in quantum transport by crystallographic axis-dependent weak localisation and exotic non-saturating negative magnetoresistance. Strikingly, quantum oscillations also reveal 3D Fermi surface with unusual interlayer coupling strength in p-SnSe, in which individual monolayers are interwoven by peculiar point dislocation defects. Our results suggest that defect engineering may provide versatile routes in improving the thermoelectric performance of the SnSe family.
SnSe 是一种很有前途的热电材料，其优值创下了纪录。然而，迄今为止，人们对 SnSe 的电子结构，尤其是自空穴掺杂机制，仍缺乏全面的了解。在这里，我们通过角分辨光电子能谱报告了 SnSe 的各向异性电子结构，其中揭示了一种独特的布丁模状价带，具有准线性能量色散。我们证明了 SnSe 中的 p 型掺杂是由 SnSe 微区的局部相分离通过界面电荷转移来实现的。布丁模带的多能谷性质在量子输运中表现为各向异性的弱局域化和奇异的非饱和负磁阻。引人注目的是，量子振荡也揭示了 p-SnSe 中具有不寻常的层间耦合强度的 3D 费米表面，其中个别单层由奇特的点位错缺陷交织在一起。我们的结果表明，缺陷工程可能为改善 SnSe 族的热电性能提供多种途径。
