Probing the charged defects in single-layer WS2 at atomic level

Abstract

Structural defects in two-dimensional materials offer an effective way to engineer their functionalities. In-situ local measurements to build the structure-function relationship are crucial for future device technology. Here, we present a comprehensive study of intrinsic defects in single-layer WS2 grown by chemical vapor deposition using a combination of scanning tunneling microscopy/spectroscopy, non-contact atomic force microscopy and density functional theory calculations. We probed the rarely observed positively charged defects and the intersection of adjacent charging rings at sufficiently high bias caused by subsurface defects. We also directly identified and visualized the widely observed negatively charged defects as chalcogen vacancies-related defects. The results reported here will guide future efforts of targeted defect engineering and doping of the single-layer transition metal dichalcogenides.