AVS 46th International Symposium
    Surface Science Division Tuesday Sessions
       Session SS3-TuA

Paper SS3-TuA9
Ion-Enhanced Surface Diffusion: Experiment and Simulation

Tuesday, October 26, 1999, 4:40 pm, Room 607

Session: Diffusion on Surfaces
Presenter: E.R. Blomiley, University of Illinois, Urbana
Authors: E.R. Blomiley, University of Illinois, Urbana
Z. Wang, University of Illinois, Urbana
E.G. Seebauer, University of Illinois, Urbana
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Low-energy ion enhancement of thin film deposition has become an increasingly widespread technique for lowering growth temperatures and improving film properties. Rational process optimization has remained difficult, however, because the beneficial effects of enhanced surface diffusion are often opposed by the deleterious effects of sputtering and ion embedding. Good explanations for important aspects of the governing physical processes remain lacking. We have recently reported for the first time direct quantitative measurements of low-energy (<70 eV) ion-enhanced diffusion, using the Ge/Si(111) adsorption system with noble gas ions as the bombarding species. The present work extends that work to examine the effects of incident bombardment angle. Experiments with second harmonic microscopy show that below about 750°C, diffusional enhancement increases monotonically as the incident angle increases from normal toward grazing. However, above 750°C diffusional effects change nonmonotonically in a manner more akin to sputtering yields. Molecular dynamics simulations show these effects arise from ion-induced adatom-vacancy pair formation.