Breaking Inversion Symmetry in 2D Semiconductors by Built-In Electric Fields across the van der Waals Metal-Semiconductor Interface.

Xia, Chuansheng; Yang, Xinyu; Cui, Qiannan; Huang, Chaoyang; Wang, Rui; Li, Yuanyuan; Wang, Xiaoxuan; Gu, Bing et al. · ACS Nano · 2026

basic_science · Level V

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Abstract

As important building blocks of integrated optoelectronic chips, most multilayer and bulk 2D layered semiconductors undertake out-of-plane inversion symmetry, which limits their multifunctional applications. Here, we propose a facile interfacial engineering means of breaking such inversion symmetry by built-in electric fields across the semiconductor-metal van der Waals heterointerface. Broken inversion symmetry of 2H WS<sub>2</sub> layers has been experimentally confirmed by strong second harmonic generation (SHG) in fabricated bulk WS<sub>2</sub>/Au heterostructures. Through correlated SHG, atomic force, and surface potential mapping measurements and density function theory simulation (DFT), we unambiguously confirm the proposed physical mechanism. These results provide more possibilities of utilizing a 2D semiconductor/metal heterostructure to construct multifunctional integrated optoelectronic chips.