AVS 50th International Symposium
    Nanometer Structures Thursday Sessions
       Session NS-ThM

Paper NS-ThM10
Adatom Hopping Induced by Tunneling Electrons: Br on Si(100)-(2x1)

Thursday, November 6, 2003, 11:20 am, Room 308

Session: Advances in Scanning Probes
Presenter: K.S. Nakayama, University of Illinois at Urbana-Champaign
Authors: K.S. Nakayama, University of Illinois at Urbana-Champaign
E. Graugnard, University of Illinois at Urbana-Champaign
J.H. Weaver, University of Illinois at Urbana-Champaign
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Tunneling electrons from the tip of a scanning tunneling microscope can be used to induce adatom hopping on Br-terminated Si(100)-(2x1) at low current and without voltage pulses. Hopping does not occur when electrons tunnel from a sample to a tip. The threshold energy is +0.8 V, and tunneling spectroscopy shows antibonding Si-Br states 0.8 eV above the Fermi level. Electron capture in these states is a necessary condition for hopping, but repulsive adsorbate interactions that lower the activation barrier are also required. Such interactions are strong near saturation for Br but are insufficient when the coverage is low or when Br is replaced by Cl.