Atomic desorption process in nanometre-scale electron-beam drilling of MgO in high-resolution transmission electron microscopy

Nanometre-scale electron-beam drilling has been performed on vacuum-deposited single-crystal magnesium oxide films in a 200 kV high-resolution transmission electron microscope with a thermionic gun. Holes formed through a surface mass-loss mechanism. Surface atomic diffusion and desorption in hole widening at the drilling were observed in situ dynamically at a spatial resolution of 0.2 nm and a time resolution of 1/60 s. It was found that, first, most of surface atoms begin to diffuse around steps on a surface owing to the electron irradiation and, subsequently, they desorb to vacuum at weakly bonded positions such as steps, kinks and isolated positions at the surfaces.