Exploring the origins of native defects on MoS2 surfaces using STM

초록

e, has attracted significant attention since the discovery of graphene. It is considered a promising material for future electronic and optoelectronic devices, although its performance is strongly influenced by defects and impurities. Natural MoS₂ contains a high density of such defects and impurities, the origins of which remain unclear despite extensive research. Identifying and effectively controlling these defects is crucial for improving device performance. In this study, we investigated the defects on pristine surfaces of natural MoS₂ using a scanning tunneling microscope (STM). The pristine MoS₂ surface was prepared under ultra-high vacuum and ambient conditions via exfoliation at room temperature. Along with atomic-scale dark features attributed to S and molybdenum Mo vacancies, two distinct types of nanometer-scale defects were observed. These nanometer-scale defects exhibited a pronounced bias dependence in STM imaging. In empty-state images, both defects appeared dark, making them indistinguishable. However, in filled-state images, they displayed contrasting characteristics: one remained dark, while the other showed a unique shape with a bright protrusion surrounded by a dark ring. Interestingly, these defects transformed into one another during scanning, suggesting they originate from the same species with different adsorption configurations. The nature and relative stability of these nanometer-scale defects are further examined in this study.