Energetics of surface atomic processes and effects on growth of ultrathin films and nanoislands

摘要

Real surfaces of a crystal, especially those of nanometer in size, have many steps and all types of lattice imperfections. Moreover, there are atoms of different atomic environments: adatoms sit at a flat tenace, kink-site atoms sit in kink sites, and step-edge atoms of various coordination numbers sit in different step-edge sites. Using field-ion and atom-probe field-ion microscopy, it is possible to measure site specific binding energies of these surface atoms, and determine the mechanisms and activation energies of the various elementary surface atomic processes, i.e. surface diffusion. For kink-site atoms, our measurements with several metals find the binding energy to be equal to the cohesive energy of these metals. Atoms at other sites have slightly smaller binding energies. However, they are not proportional to the coordination numbers of the atoms, as assumed in many calculations. Such information will not only shed light on the binding mechanisms of solids, but is also needed for understanding the mechanisms of growth phenomena, such as crystal growth and epitaxial growth of thin films and nanoislands.