Unraveling the Decomposition Pathways of LaS-TaS$_2$ Misfit-Layered Compound Nanostructures under Extreme Electrical Currents by In Situ TEM

Nanostructures of the misfit-layered compound (MLC) LaS-TaS$_2$ 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$_2$ 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$_2$ 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.