  Effect of an anisotropic detachment on a heteroepitaxial island shape is
studied by means of a kinetic Monte Carlo simulation of a square lattice gas
model. Only with molecular deposition followed by surface diffusion, islands
grow in a ramified dendritic shape, similar to DLA. Introduction of molecular
detachment from edges makes islands compact. To understand an anisotropic
island shape observed in the experiment of pentacene growth on a
hydrogen-terminated Si(111) vicinal surface, asymmetry in detachment around the
substrate step is assumed. Edge molecules detach more to the higher terrace
than to the lower terrace. The island edge from which molecules are easy to
detach is smooth and the one hard to detach is dendritic. If islands are close
to each other, islands tend to align in a line, since detached molecules from
the smooth edge of the right island are fed to the dendritic and fast growing
edge of the left island.
