“Phase transformations of nanoscale systems using In Situ TEM”
Many nanoscale systems exhibit phase transformations in response to stimuli, which subsequently change the material properties of the systems, providing opportunities to create functional devices. Here, we use in situ transmission electron microscopy (TEM) as a tool to study how phase transformations occur, deviate, and are controlled at the nanoscale under either thermal or electrical stimuli. I will discuss two examples of phase transformation: IBM’s confined phase change memory (PCM) cells with a surfactant layer, which showed a record endurance of 2x1012 programming cycles, and metallic glass nanostructures that are used to test the limits of classical nucleation theories. In the PCM example, we demonstrate a surprising self-healing property, enabled by the symmetric design of the device. With the nanoscale metallic glasses, we observe that crystallization can be greatly affected by the nanocscale confinement and the underlying local structure of the glass. In both examples, atomic scale in situ TEM investigations uniquely reveal detailed and unexpected phenomena, guiding us to build better models and theories for nanoscale phase transformations. I will also discuss phase transformations of two-dimensional transition metal dichalcogenides induced by electrochemical intercalation of Li+ and their energy applications, as well as a one-dimensional topological superconductor.