An FIM and STM study of the dynamical behavior of solid surfaces

Abstract

Atoms at the surface are by no means static. When the temperature of a solid is increased gradually, surface atoms may start to dissociate from their lattice sites and diffuse on the surface around or slightly above the room temperature. This diffusion involves with single adatoms on terraces and ledge atoms along lattice steps. It may involve with small atomic clusters or even large islands. At a higher temperature, collective effects may become important and step as well as surface roughening, structure phase transitions and collective movements of surface atoms may start to occur. A similar behavior can occur for atoms condensed on the surface. This dynamical behavior of the solid surface can be described by the occurence of a series of elementary atomic processes or steps which are common to different surface phenomena involving the transport and movement of surface atoms. These phenomena include epitaxial growth of thin films, crystal growth, changes of the shape of crystals and surface layers, surface atomic reconstructions, and surface enhanced chemical reactions, etc. We have been studying in atomic details both the mechanisms and energetics of various surface atomic processes using the field ion microscope. Recently we have also started to use the scanning tunneling microscope and molecular dynamics to study the same problem. Our very recent works include finding a new atomic-exchange-displacement mechanism in adatom diffusion on the Ir(001) and the formation as well as two diffusion modes of and Ir-Re dimer-vacancy complex on the Ir(001). We have also measured the dissociation energies of step edge atoms at the Ir(001), binding energies of Ir atoms in kink sites and adsorption sites of the Ir(001) surface, and the formation energies of single- and di-vacancies at the Si(111) (7 × 7) surface etc. Details of these studies can be found in the papers listed in the references below and some of our upcoming papers. These works were done in collaboration with Chonglin Chen, Jiang Liu, C.S. Chang, R.L. Lo and others