Abstract
The crystal shape of Ni particles, dewetted in the solid state on sapphire substrates, was
examined as a function of the partial pressure of oxygen (P(O2)) and iron content using
scanning and transmission electron microscopy. The chemical composition of the
surface was characterized by atom-probe tomography. Unlike other FCC equilibrium
crystal shapes, the Ni crystals containing little or no impurities exhibited a facetted
shape, indicating large surface anisotropy. In addition to the {111}, {100} and {110}
facets, which are usually present in the equilibrium crystal shape of FCC metals, high
index facets were identified such as {135} and {138} at low P(O2), and {012} and
{013} at higher P(O2). The presence of iron altered the crystal shape into a truncated
sphere with only facets parallel to denser planes. The issue of particle equilibration is
discussed specifically for the case of solid-state dewetting.
