Defect engineering in 2D materials: atomic scale properties and interaction with molecules – DEFINE2D

Imperfections in two-dimensional (2D) materials are unavoidable. To clarify the impact of such defects on materials properties and to further control or engineer them to reach specific structure-property correlation, is a daunting task. The goal of this DEFINE2D project is to elucidate the atomic nature of defects in selected 2D materials and embody viable defect engineering strategies to create verifiable new materials properties. Our materials systems will include transition metal dichalcogenides (TMD), graphene, and black phosphor, in bulk or ultrathin film forms. Intrinsic or extrinsic defects, including atomic vacancies and domain boundaries, are first created at surfaces by precise heat, laser, ion beam treatments or substrate choice. Doping and strain will then be introduced through atomic substitution by atomic nitrogen plasma, molecular adsorption, and alkali intercalation, resulting in tuning of materials functions. Our integrated approach centers on our key strength of atom-resolved scanning probe microscopy and spectroscopy, and is complemented by optical measurements and our unique precise in-situ defect generation capability. Experimental data and theoretical modeling will work synergistically. The expected breakthrough is to understand the electronic states associated with defects at unprecedented spatial resolution, and to engineer such electronic states through doping and strain. New material functionalities, such as enhanced hydrogen evolution on N-substituted vacancy-populated MoS2, or tip-induced light emission from exciton recombination at engineered defects of WSe2, will be explored.