  Self-assembled topological structures of post-processed two-dimensional
materials exhibit novel physical properties distinct from those of their parent
materials. Herein, the critical role of desulphurization on self-assembled
topological morphologies of molybdenum disulfide ($MoS_2$) monolayer sheets is
explored using molecular dynamics (MD) simulations. MD results show that there
are differences in atomic energetics of $MoS_2$ monolayer sheets with different
desulphurization contents. Both free-standing and substrate-hosted $MoS_2$
monolayer sheets show diversity in topological structures such as flat surface,
wrinkles, folds and scrolls, depending on the desulphurization contents, planar
dimensions and ratios of length-to-width of $MoS_2$ monolayer sheets.
Particularly, at the critical desulphurization contents, they roll up into
nanotube morphology, consistent with previous experimental observations.
Moreover, the observed differences in the molecular morphological diagrams
between free-standing and substrate-hosted $MoS_2$ monolayer sheets can be
attributed to unique interatomic interactions and van der Waals interactions in
them. The study provides important insights into functionalizing structural
morphological properties of two-dimensional materials, e.g., $MoS_2$, via
defect engineering.
