Zhao Mali, Kim Dohyun, Lee Yongjoon, Ling Ning, Zheng Shoujun, Lee Young Hee, Yang Heejun
Department of Energy Science, Sungkyunkwan University, Suwon 16419, Korea.
Institute for Basic Science, Center for Integrated Nanostructure Physics, Suwon 16419, Korea.
ACS Nano. 2021 Mar 23;15(3):5397-5404. doi: 10.1021/acsnano.1c00030. Epub 2021 Mar 4.
Thermoelectricity has been investigated mostly on the macroscopic scale despite the fact that its origin is linked to the local electronic band structure of materials. While the role of thermopower from microscopic structures (, surfaces or grain boundaries) increases for emerging thermoelectric materials, manipulating thermoelectric puddles, spatially varying levels of thermoelectric power on the nanometer scale, remains unexplored. Here, we illustrate thermoelectric puddles that can be harnessed the stacking order and electronic screening in graphene. The local thermoelectric elements were investigated by gate-tunable scanning thermoelectric microscopy on the atomic scale, revealing the roles of local lattice symmetry, impurity charge scatterings, and mechanical strains in the thermopower system. The long-range screening of electrons at the Dirac point in graphene, which could be reached by spectroscopy, allowed us to unveil distinct thermoelectric puddles in the graphene that are susceptible to the stacking order and external strain. Thus, manipulating thermoelectric puddles a lattice symmetry and electronic engineering will realize practical thermopower systems with low-dimensional materials.
尽管热电效应的起源与材料的局部电子能带结构相关，但对热电效应的研究大多集中在宏观尺度上。对于新兴的热电材料，微观结构（如表面或晶界）产生的热功率的作用日益增强，然而，对纳米尺度上空间变化的热电功率——即热电“水坑”的操控仍未得到探索。在此，我们展示了可利用石墨烯中的堆叠顺序和电子屏蔽来实现的热电“水坑”。通过在原子尺度上进行栅极可调谐扫描热显微镜研究了局部热电元件，揭示了局部晶格对称性、杂质电荷散射和机械应变在热功率系统中的作用。通过光谱学能够实现的石墨烯狄拉克点处电子的长程屏蔽，使我们得以揭示石墨烯中不同的热电“水坑”，这些“水坑”易受堆叠顺序和外部应变的影响。因此，通过晶格对称性和电子工程来操控热电“水坑”，将实现基于低维材料的实用热功率系统。
