from square β-FeSe decorated with Mo adatoms*

Two-dimensional (2D) materials have generated interest in the scientific community because of the advanced electronic applications they might offer. Powerful electron beam microscopes have been used not only to evaluate the structures of these materials, but to manipulate them as well, by forming vacancies and nano-fragments or joining nano-islands together. In this presentation I will show a movie in which the electron beam in a scanning transmission electron microscope (STEM) can be used in yet another way: to mediate the synthesis of 2D 1H-MoSe₂ from Mo-decorated 2D β-FeSe and simultaneously image the process on the atomic scale. Prior to committing microscope and materials resources to this project, the choice of reactants was first evaluated as a reasonable system for this proof of concept synthesis via quantum mechanical calculations. These calculations will be described in detail and include a methodology for finding a reaction path to forming a stable 1H-MoSe₂ nucleation kernel within pure β-FeSe in which the pertinent energy barriers are smaller than the energy that can be supplied by a STEM electron beam.