Keithley Symposium

With its unique combination of spatial and temporal resolution, transmission electron microscopy presents exciting opportunities to explore reaction kinetics and mechanisms. Reactive gases can be flowed over a heated sample in situ within the microscope, while liquid phase reactions can be probed within enclosures that confine the liquid between electron-transparent membranes. Continuous imaging allows measurement of local reaction kinetics and the response to changes in conditions such as gas pressure, temperature or applied voltage; it is also possible to visualize intermediate configurations, even if fairly short-lived. Through examples including catalytic formation of nanowires, electrochemical nucleation and growth of copper, and phase transformations in epitaxial metal islands on graphene, I will show how information from in situ microscopy experiments can help to explore and quantify reaction mechanisms. Of particular interest are systems that are limited in spatial extent, where the microscope can view the entire reacting volume. I will discuss measurements of nucleation, dislocation formation and interfacial step flow in such nanoscale systems, and I will also discuss the calibrations needed to model measurements made in situ and connect them to larger scale, real-world phenomena.