Unveiling sulfur vacancy pairs as bright and stable color centers in monolayer WS2
Huacong Sun, Qing Yang, Jianlin Wang, Mingchao Ding, Mouyang Cheng, Lei Liao, Chen Cai, Zitao Chen, Xudan Huang, Zibing Wang, Zhi Xu, Wenlong Wang, Kaihui Liu, Lei Liu, Xuedong Bai, Ji Chen, Sheng Meng, Lifen Wang
Abstract
Color centers, arising from zero-dimensional defects, exploit quantum confinement to access internal electron quantum degrees of freedom, holding potential for quantum technologies. Despite intensive research, the structural origin of many color centers remains elusive. In this study, we employ in-situ cathodoluminescence scanning transmission electron microscopy combined with integrated differential phase contrast imaging to examine how defect configuration in tungsten sulfide determines color-center emission. Using an 80-kV accelerated electron beam, defects were deliberately produced, visualized, excited in situ and characterized in real time in monolayer WS2 within hBN|WS2 | hBN heterostructures at 100 K. These color centers were simultaneously measured by cathodoluminescence microscopy and differentiated by machine learning. Supported by DFT calculations, our results identified a crucial sulfur vacancy configuration organized into featured vacancy pairs, generating stable and bright luminescence at 660 nm. These findings elucidate the atomic-level structure-exciton relationship of color centers, advancing our understanding and quantum applications of defects in 2D materials. The controlled fabrication and microscopic understanding of quantum emitters in 2D materials remain challenging. Here, the authors report the production and characterization of defects in monolayer WS2 via cathodoluminescence electron microscopy, identifying sulfur vacancy pairs as bright and stable emitters at 660 nm.