Duan Research Group

Hetero-integrated Nanostructures and Nanodevices


Highly-anisotropic optical and electrical properties in layered SnSe

Shengxue Yang, Yuan Liu, Minghui Wu, Li-Dong Zhao, Zhaoyang Lin, Hung-chieh Cheng, Yiliu Wang, Chengbao Jiang, Su-Huai Wei, Li Huang, Yu Huang, Xiangfeng Duan

Nano Res. 11, 554-564 (2018)

Anisotropic materials are of considerable interest because of their unique combination of polarization- or direction-dependent electrical, optical, and thermoelectric properties. Low-symmetry two-dimensional (2D) materials formed by van der Waals stacking of covalently bonded atomic layers are inherently anisotropic. Layered SnSe exhibits a low degree of lattice symmetry, with a distorted NaCl structure and an in-plane anisotropy. Here we report a systematic study of the in-plane anisotropic properties in layered SnSe, using angle-resolved Raman scattering, optical absorption, and electrical transport studies. The optical and electrical characterization was direction-dependent, and successfully identified the crystalline orientation in the layered SnSe. Furthermore, the dependence of Raman-intensity anisotropy on the SnSe flake thickness and the excitation wavelength were investigated by both experiments and theoretical calculations. Finally, the electrical transport studies demonstrated that few-layer SnSe field-effect transistors (FETs) have a large anisotropic ratio of carrier mobility (∼5.8) between the armchair and zigzag directions, which is a record high value reported for 2D anisotropic materials. The highly-anisotropic properties of layered SnSe indicate considerable promise for anisotropic optics, electronics, and optoelectronics.
UCLA, Department of Chemistry and Biochemistry
607 Charles E. Young Drive East, Box 951569
Los Angeles, CA 90095-1569
E-mail: xduan@chem.ucla.edu