Three-Dimensional Atomic Scale Insights into Unconventional Fragmentation of Two-Dimensional ReS ₂ Monolayers into Molecular Clusters

Two-dimensional (2D) transition metal dichalcogenides (TMDs) typically degrade through atom-by-atom removal under chemical or electron beam stimuli. Here, we report a fundamentally different degradation pathway in CVD-grown monolayer rhenium disulfide (ReS 2 ), whereby the lattice fragments into stable, discrete molecular clusters under electron irradiation and when etched with a 1 M KOH solution. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy reveals the atomic arrangement of these clusters, while single-particle analysis reconstruction resolves their three-dimensional structure with near-atomic precision. Time-resolved imaging demonstrates that both the transfer process and beam-induced effects drive the lattice-to-cluster transformation. These findings reveal an unconventional degradation pathway in ReS 2, distinct from other 2D TMDs, where its molecular-like bonding drives the production of well-defined Re–S clusters, thereby providing a direct link between 2D materials science and transition-metal cluster chemistry.