AVS 56th International Symposium & Exhibition
    Surface Science Thursday Sessions
       Session SS-ThP

Paper SS-ThP17
Evolution of Microscopic Surface Deformation on Si(111) due to Low Energy Ion Bombardment

Thursday, November 12, 2009, 6:00 pm, Room Hall 3

Session: Surface Science Poster Session
Presenter: P. Piercy, University of Ottawa, Canada
Authors: P. Piercy, University of Ottawa, Canada
J.M. David, University of Ottawa, Canada
D. Pohl, University of Ottawa, Canada
Correspondent: Click to Email
Low energy ion bombardment of a crystalline solid may cause a variety of surface and subsurface damage. At moderately elevated sample temperatures to prevent amorphization, the sputtering process may leave a step-and-terrace morphology, but surface reconstruction may be disordered and a distribution of ion-induced defects may remain in a shallow, inhomogeneously strained, subsurface layer. After low energy argon ion bombardment on Si(111), we use a spot profile analysis of low energy electron diffraction data at in-phase conditions to measure a low amplitude, continuous distribution of surface height, which occurs in addition to atomic-height steps and other short-range atomic disorder at the surface. Measurements over a range of ion dose, ion energy, and sample temperature, are attributed to surface deformation due to strain around subsurface defects. For bombardment of the Si(111) surface at 600K by 230 eV argon ions with dose increasing in the range 1015-1016 cm-2, we find a continuous surface height distribution, whose contribution to the interface width increases from hundredths of an Angstrom up to ≈ 0.1 Å, correlated laterally over tens of Angstroms. These results may be interpreted in terms of an elastic continuum model of the solid, with defects created below the surface by independent ion bombardment events modeled simply by a distribution of small inclusions. At a higher surface temperature of 800 K, the surface deformation after the same ion energy and doses as above gives interface width contribution w increasing to 0.07 Å; with further bombardment to a dose of 1017 cm-2, w grows to 0.15 Å. At a higher ion beam energy of 730 eV, w increases to a saturation value of 0.18 Å after an argon ion dose of ≈2·1016 cm-2. Implications for the evolution of the buried defect distribution will be discussed.