Electron Ptychography for Atom-by-Atom Quantification of 1D Defect Complexes in Monolayer MoS 2
This study combines experimental imaging and DFT simulations to investigate the formation and electronic properties of line defects in monolayer MoS₂. Using high-resolution electron ptychography with 4D-STEM, it was observed the formation of one-dimensional (1D) defect complexes, including sulphur vacancy lines and rhenium (Re) dopant lines, with sub-angstrom precision. It was found that sulphur single-vacancy (S-SV) lines form at a vacancy density of 5 × 1013 cm-2 and transition to double-vacancy (S-DV) lines beyond 8 × 1013 cm-2, while Re-dopant lines emerge at concentrations above 3 × 1013 cm-2.
DFT calculations revealed that sulphur vacancies cause charge redistribution, increasing electron density around neighbouring Mo atoms and reducing their effective charge which influences the lattice displacements, particularly in S-DV lines. Re-dopant lines induced local lattice expansion but had little effect on charge states. Additionally, spin-polarized calculations showed that Re-dopant lines could exhibit multiple spin configurations at room temperature, and in-gap states observed in S-DV and S-interstitial-vacancy lines confirmed their metallic nature.
These findings highlight the potential of defect engineering to tune the electronic properties of 2D materials.
Authors: Leyi Loh, Shoucong Ning, Daria Kieczka, Yuan Chen, Jianmin Yang, Zhe Wang, Stephen J. Pennycook, Goki Eda, Alexander L. Shluger, Michel Bosman