AVS 52nd International Symposium
    Surface Science Wednesday Sessions
       Session SS1-WeA

Paper SS1-WeA8
Cyclic Transformation of 1-D Structures during Homoepitaxy of Si(5 5 12)-2x1

Wednesday, November 2, 2005, 4:20 pm, Room 200

Session: Surface Structure and Morphology Modification
Presenter: H. Kim, Chonbuk National University, Korea
Authors: H. Kim, Chonbuk National University, Korea
Y. Cho, Chonbuk National University, Korea
J.M. Seo, Chonbuk National University, Korea
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In the homoepitaxy of Si(5 5 12)-2x1 at a finite temperature, 500 C, it has been found by STM that Si overlayer grows in the layer-by-layer fashion and there are three distinct stages, such as dimer-filling, faceting, and valley-filling stages, for recovering Si[5 5 12]-2x1. In each transformed stage, the number of dangling bonds as well as 1-D symmetry with three kinds of reconstructed features, such as honeycomb(H) chain, tetramer(T) row, and dimer-facing-adatoms(D/A) row, are always preserved on the reconstructed surface under a quasi-equilibrium state with deposited Si atoms. The simple rule observed in this 1-D structural transformation is as follows: A honeycomb(H) chain is broken into a tetramer(T) row by the compressive stress, a T row is split to a dimer-facing-adatoms(D/A) row by the tensile stress, and a D/A row is transformed to a H chain by two adsorbed-dimers. Only in the last transformation, the center of 1-D feature shifts in the direction of [-6-6 5] by 3.04 A. It takes only 28 atoms per unit cell to recover the identical, planar and reconstructed Si(5 5 12)-2x1. The reason why such an amount of Si atoms for recovering the original surface is much smaller than that of surface atoms involving in the reconstruction of Si(5 5 12) is in the fact that the exact growth-direction is not along [5 5 12] but along [-1-1 2]. One-cycle of homoepitaxy is completed when seven (111) double-step edges of a unit-cell of Si(5 5 12)-2x1 are filled with two dimers respectively, and results in the effective height increment of 1.36 A and horizontal shift of 3.04 A toward [-6-6 5].