IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Semiconductors Monday Sessions
       Session SC+SS-MoA

Paper SC+SS-MoA6
STM Studies of the Ca/Si(111) System

Monday, October 29, 2001, 3:40 pm, Room 122

Session: Semiconductor Surfaces
Presenter: J.W. Dickinson, Virginia Commonwealth University
Authors: J.W. Dickinson, Virginia Commonwealth University
S.C. Erwin, Naval Research Laboratory
J.A. Carlisle, Argonne National Laboratory
A.A. Baski, Virginia Commonwealth University
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The Ca/Si(111) system forms a series of odd-order nx1 (n = 3,5,7,etc.) reconstructions that culminate with a 2x1 phase at 0.5 ML.@footnote 1@ Similar to group I metals, group II Ca forms a 3x1 phase at low coverage, where a previous model based upon Si honeycomb-chain-channel (HCC) chains accounts well for the observed STM data. In contrast to the group I metals that form the 3x1 phase at 1/3 ML, however, Ca forms this phase at 1/6 ML,@footnote 2@ presumably due to the fact that Ca has twice the number of available electrons. Another interesting behavior unique to Ca is the presence of a 2x1 phase that reaches completion at 1/2 ML. We have proposed a model for the 2x1 phase based upon pi-bonded Seiwatz Si chains, where Ca rows form between the Si chains. The variety of odd-order nx1 phases (5x1, 7x1, etc.) that occur between these end-point 3x1 and 2x1 phases are then appropriate combinations of the 3x1 HCC chains and 2x1 Seiwatz chains. For example, a 5x1 unit cell is composed of one HCC chain and one Seiwatz chain, where two Ca rows are found per unit cell. Calculated surface energies based on the HCC and Seiwatz models correctly predict that for increasing Ca coverage, the 3x1, 5x1, and 2x1 phases each appear as stable phases. @FootnoteText@ @footnote 1@ A.A. Baski, S.C. Erwin, M.S. Turner, K.M. Jones, J.W. Dickinson, J.A. Carlisle, Surf. Sci. 476, 22 (2001). @footnote 2@ G. Lee, D. Shin, J. Koo, H. Kim, S. Hong, Abstract #S25-8, APS 2001 March meeting.