Abstract
Freely floating crystals are not common during growth. In most cases,
the crystals are in contact with a foreign body, such as other crystals,
the wall or bottom of the growth system or a mount to keep the specimen
fixed. Then, growth steps are often preferentially nucleated at the intersection
line between the crystal surface and the foreign body. In this study the
phenomenon of contact nucleation is investigated by kinetic Monte Carlo
simulation and analytical description. Depending on supersaturation, the
length of the contact line and the different edge free energies involved,
six modes of crystal growth are encountered: "free growth", thermally and
kinetically rough growth, mono and poly contact nucleation and birth-and-spread
growth. Phase diagrams displaying the existence domains of the different
growth modes are constructed from Monte Carlo simulation results as well
as from analytical expressions. Growth rates and the slope of the crystal
surface adjacent to the foreign body are measured by simulation and calculated
using a microscopic description of contact nucleation. The "free growth"
and both rough growth modes are analysed in terms of the kinematic wave
theory for crystal shape evolution, in which the junction between crystal
and foreign body acts as a velocity source that locally accelerates growth.