Bulk-Surface Vacancy Exchange and Thermal Smoothing of Pt(111) Direct Observations of Nanoscale Self-Assembly and Pattern Formation on Solid Surfaces Atom Diffusion Controls Dynamics of Surface Phase Transition on Si (111) Low Energy Electron Microscope Study of Si(001) Etching by Molecular Oxygen Boron-Induced Step Faceting and Stripe Formation on Si(001) * Work supported by the U. S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Science and Engineering