Coarsening of Unstable Surface Features during Fe(001) Homoepitaxy

The evolution of the surface potential during homoepitaxial growth of Fe(001) is studied by scanning tunneling microscopy and reflection high energy electron diffraction. The observed morphology exhibits a non-self-affine collection of moundlike features that maintain their shape but coarsen as growth proceeds. The characteristic feature separation $L$ is set in the submonolayer regime and increases with thickness $t$ as $L(t)\ensuremath{\sim}{t}^{0.16\ifmmode\pm\else\textpm\fi{}0.04}$. During the coarsening phase, the mounds are characterized by a magic slope and a lack of reflection symmetry. These observations are shown to be described by a continuum growth equation without capillarity.