AVS 53rd International Symposium
    Surface Science Tuesday Sessions
       Session SS-TuP

Paper SS-TuP9
Neutralization and Ionization during Impact of Low Energy Si@super +@ with Surfaces

Tuesday, November 14, 2006, 6:00 pm, Room 3rd Floor Lobby

Session: Surface Science Poster Session
Presenter: X. Chen, University of California, Riverside
Authors: X. Chen, University of California, Riverside
Z. Sroubek, University of California, Riverside
J.A. Yarmoff, University of California, Riverside
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The interaction of low energy semiconductor ions with solid surfaces has been largely unexplored. In this work, 1-5 keV Si@super +@ ions are used to induce direct recoil (DR) from Al(100) and Si(111), and are scattered from electropositive and electronegative adatoms adsorbed on these surfaces. In the DR experiments, significant yields of fast, monoenergetic doubly and triply charged Al and Si ions are produced, which is in contrast to the secondaries formed during bombardment by noble gas ions. The Al@super 2+@ and Al@super 3+@ are attributed to an efficient promotion of Al 2p level during the electronically nearly-symmetric Si-Al collision, and subsequent shake-off processes. The yield of triply charged ions in DR from Si is reduced from that of Al, due to the more symmetric electronic structure. Si@super +@ ions were backscattered from submonolayers of Cs and I deposited onto Al(100) and Si(111). Because of the high ionization energy of Si, resonant charge transfer would be expected to completely neutralize the scattered projectiles. A considerable fraction of the Si backscatters from the adatoms as positive and negative ions, however. Mechanisms responsible for the ion formation will be discussed.