Lead on graphite: Equilibrium shape, crystal growth, melting and the early stages of oxidation

Abstract

Micron-sized lead particles have been grown on graphite and have been observed dynamically in a UHV scanning electron microscope. Secondary electron images on videotape have shown the solidification of liquid droplets into epitaxial orientations, the evolution towards the equilibrium shape containing {111} and {100} facets and the diminution of these facets as the melting point is approached. Kinetically determined growth shapes have been observed which show that these facets grow much more slowly than other (rough) faces. Very flat tabular (111) crystals are also formed which exhibit delayed melting phenomena. The early stages of oxidation of equilibrium-shaped crystals results in an increase in size of {100} facets at the expense of {111} facets. These phenomena are discussed briefly.