Thermally Driven Formation of Multiphase, Mixed-Dimensional Architectures from TaSe ₃ Nanoribbons

Tantalum-selenium compounds, particularly TaSe₂ and TaSe₃, are promising materials for electronics and quantum technologies due to their charge density wave and topological properties, and they are also candidates for energy storage and electrocatalysis applications. In this study, we investigate the thermally driven structural evolution of TaSe₃ nanoribbons using <i>in situ</i> scanning transmission electron microscopy (STEM). Low-kV STEM experiments reveal a complex nanoscale transformation pathway in which TaSe₃ nanoribbons convert into multiphase, mixed-dimensional (0D-1D) tantalum-selenium architectures. Aberration-corrected STEM enables direct visualization of the underlying atomic rearrangements, while electron energy loss spectroscopy and DFT calculations corroborate the identity and stability of the product phases. Our results uncover a detailed mechanism: selenium loss from TaSe₃ nanoribbons initiates surface conversion to TaSe₂, which, as temperature increases, progressively continues into the nanoribbon interior. Thicker regions of TaSe₂ delaminate and detach from the core material, forming a porous TaSe₂ shell. At 1200 °C, the core restructures into discrete ∼20 nm Ta-self-intercalated TaSe₂ nanoparticles. This core-shell transformation, driven by nanoscale confinement effects, differs markedly from the bulk decomposition pathway of TaSe₃ and highlights the impact of modulating selenium loss, tantalum intercalation, and the stability of intermediate structures through confinement effects. The resulting 0D-1D heterostructure of Ta-rich nanoparticles encapsulated within porous TaSe₂ tubes represents surprising and emergent complexity in a binary system. These mechanistic insights demonstrate how the controlled thermolysis of a readily accessible metal trichalcogenide precursor can yield complex, low-dimensional chalcogenide architectures.