The deposition of Mn onto Si͑001͒ 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°C three-dimensional islands of Mn or Mn x Si y form while between the islands the Si͑001͒-͑2 ϫ 1͒ 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 ͑1900͔͒ ripening theory. The average island height shows a time dependence of H ϳ t 1/4 , indicating that surface diffusion is the growth limiting process.

Data is presented for a complex structural and compositional modulation in the perovskite (NaNd)(MgW)O6. This modulation creates a large 14ap×14ap×2ap supercell (ap≈3.9 Å is the lattice parameter of the cubic perovskite aristotype) containing ordered regions with doubled (110) d-spacings in the a-b plane separated by two-dimensional periodic antiphase boundaries and accompanied by a nanocheckerboard pattern. Faint periodic modulations in Z-contrast images suggest an associated periodic variation in composition. The presence of a sodium rich impurity implies the composition of the stable perovskite is nonstoichiometric.

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The rate of growth during annealing of manganese silicide islands in the submonolayer coverage regime on the Si(001) surface has been measured by scanning tunneling microscopy. The fourth power of the growth rate is linearly dependent upon the annealing time, consistent with a diffusion limited Ostwald ripening mechanism for island growth. The growth rate has been determined for four different annealing temperatures to extract the activation energy for clustering, which has been found to be 2.6±0.2eV.