Two-dimensional (2D) materials have attracted tremendous interest due to its reduced dimensionality, suggesting great promise in micro- and nano-scale applications. For electronic and thermoelectric devices, high electrical transport properties are desired. Exploring 2D materials with high mobility and high thermoelectric figure of merit (ZT) is an important direction of current researches. Recently, monolayer α-Te is predicted be stable by theoretical calculations [Zhu et al., Phys. Rev. Lett. 119, 106101(2017)]. Unlike many traditional thermoelectric materials consisting of multinary compounds with complex crystal structure, monolayer α-Te is elemental system with simple crystal structure.

By analyzing the physical properties of monolayer α-Te, Dr. Wu Li’s group thought that monolayer α-Te should possess good thermoelectric property, which was demonstrated by the first-principles calculations. It was found that the ZT of n-type monolayer α-Te can reach 0.55-1.46 in 300-700 K, whereas the electron mobility can be as high as 2500-630 cm2/Vs. From the analysis of scattering mechanisms, the ZA phonons are found to be the dominant scattering process of electrons. Thus, by applying tensile strain, the quadratic ZA phonon dispersion is stiffened to linear, leading to the removal of the diverging thermal population of ZA phonons. Consequently, the electron mobility and ZT are enhanced. At a 4% tensile strain, in the temperature range of 300-700 K, the electron mobility can reach up to 8000-1500 cm2/Vs, while the ZT can be increased to 0.94-2.03, comparable with the state-of-the-art bulk thermoelectric materials.

Figure：(left) Electron mobility and (right) thermoelectric figure of merit of n-type monolayer α-Te under different strains.

The results were published in ACS Applied Materials & Interfaces, entitled “Strain-Induced Ultrahigh Electron Mobility and Thermoelectric Figure of Merit in Monolayer α-Te”. The first author of the paper is Dr. Jinlong Ma (now working at Huazhong University of Science and Technology). Collaborators include Fanchen Meng (co-advised by Dr. Wu Li) and Prof. Jian He from Clemson University (USA), Prof. Yu Jia from Zhengzhou University. The research was supported by the Natural Science Foundation of China, Natural Science Foundation of Guangdong Province, and the Shenzhen Science, Technology and Innovation Commission.

Since 2008, Dr. Wu Li has been engaged in the research of thermal, electrical and thermoelectric transport properties. By developing calculation methods and tools, he has greatly advanced the fields including nanoscale heat transfer and thermoelectric materials.

Paper Link：https://pubs.acs.org/doi/10.1021/acsami.0c10236