The deposition of Mn onto Si(001) in the submonolayer regime has been studied with scanning tunneling microscopy to gain insight into the bonding and energetics of Mn with Si. The as-deposited Mn films at room temperature are unstructured. Upon annealing to 300-700 degrees C three-dimensional islands of Mn or MnxSiy form while between the islands the Si(001)-(2 x 1) reconstruction becomes visible. With increasing annealing time the density of islands per surface area decreases while the average height of the remaining islands increases. The large islands grow in size at the expense of the small ones, which can be understood in the context of Ostwald [Z. Phys. Chem. 34, 495 (1900)] ripening theory. The average island height shows a time dependence of H similar to t(1/4), indicating that surface diffusion is the growth limiting process. (c) 2006 American Vacuum Society.