Dynamics, Interactions, and Collisions of Atomic Steps on Si(111) in Sublimation

The dynamics of atomic steps and the interactions between them were observed by in situ scanning electron microscopy for the sublimation of a Si(111) surface which was atomically flat on a large $(\sim 100\mu \mathrm{m}\times 50\mu \mathrm{m})$ scale. Newly nucleated widely spaced steps moved at a constant velocity. For more narrowly spaced steps, diffusion mediated step-step interactions reduced the step velocity. To further probe these interactions, steps were made to collide. In destructive collisions, steps decelerated and flattened. In constructive collisions double atomic steps were produced.