Unraveling the Decomposition Pathways of LaS-TaS Misfit-Layered Compound Nanostructures under Extreme Electrical Currents by In Situ TEM.

Nanostructures of the misfit-layered compound (MLC) LaS-TaS are brought to breakdown by application of high electrical currents within a transmission electron microscope. Imaging, diffraction, and spectroscopy techniques are employed to study their decomposition process and the resulting structures. The main decomposition route is the breakdown of the TaS layers, which induces the formation of metallic Ta on the surface of the nanostructures when the critical current density is surpassed. This observation confirms the assumption that TaS is the current-carrying layer in these types of MLCs. The different behavior of tubular 1D and 2D structures is revealed, and a metallic glass phase made of La, Ta, and S could be observed upon exceeding a threshold current. The work shows how in situ transmission electron microscopy can help understand the breakdown mechanism of electrical devices or connectors.