Cross-Sectional Imaging of the WS₂ Nanotube Formation Pathways

Recent elucidation of the synthesis mechanism of WS₂ nanotubes has raised fundamental questions about the origin of structural subtypes, imperfect nanotubes, and internal scroll-like morphologies. Although such 1D structures are observed in both laboratory and industrial batches, their formation pathways remain unclear. As applications of WS₂ nanotubes─particularly in optoelectronics─continue to expand, understanding these structural variations is essential for process optimization and performance control. Here, we develop an advanced imaging approach that combines stepwise sulfidation on a microelectromechanical-system chip with sequential cross-sectional imaging of individual nanostructures. This methodology enables time-resolved, atomic-scale correlation between the internal structure of tungsten oxide nanowhisker precursors and the resulting WS₂ morphologies. We identify multiple reaction pathways and establish direct links between precursor anisotropy and nanotube geometry, refining the sulfidation mechanism and clarifying the transformation from tungsten oxide to tungsten disulfide. These insights provide a framework for controlled synthesis of structurally optimized WS₂ nanotubes.