Island shapes in homoepitaxial growth of Pt(111)

We present a kinetic model for the homoepitaxial growth of Pt(111) capable of reproducing the experimentally observed compact island shapes in a set of kinetic Monte-Carlo simulations. We propose that an anomaly in the binding of single atoms to the two types of close packed steps causes the appearance of triangular islands around 400 K. The anomaly is that the single atoms bind the strongest to the more stable close packed step. We argue, that this cannot be the cage for longer rows of atoms attached to the steps, and assuming that dimers bind the strongest to the less stable close packed step, we show this causes the appearance of triangular islands of the opposite orientation around 650 K.