Defect Heterogeneity in Monolayer WS2 Unveiled by Work Function Variance - Wang, Xinyun; Dan, Jiadong; Hu, Zhenliang; Leong, Jin Feng; Zhang, Qi; Qin, Ziyu; Li, Shisheng; Lu, Junpeng; Pennycook, Stephen J; Sun, Wanxin; Sow, Chorng Haur (Chemistry of materials, 2019)