Strain-Modulated Adatom and Surface Vacancy Pair Interactions

[+] Author and Article Information
P. Liu, D. Kouris

 Department of Mechanical Engineering, University of Wyoming, Box 3295, Laramie, WY 82071

R. V. Kukta

 Department of Mechanical Engineering, State University of New York, Stony Brook, NY 11794-2300

J. Appl. Mech 72(3), 400-407 (Oct 06, 2004) (8 pages) doi:10.1115/1.1875392 History: Received October 27, 2003; Revised October 06, 2004

Adsorbed atoms (adatoms) and vacancies have a significant role to play in the physics of surfaces and the mechanisms of film growth on a substrate. This paper investigates the effect of applied or residual strain on the energetic interaction between pairs of adatoms and vacancies. The analysis is based on a continuum-level point-defect model, where adatoms and vacancies have strain-dependent properties. Atomistic calculations are used to evaluate the defect properties for Si(111). The result is used as input for the defect model in order to investigate the strength and character of the interaction versus strain, separation distance, and relative orientation of the defects. It is found that strain may cause the defects to align in certain direction and modulate their interaction between repulsion and attraction, providing a mechanism for controlled building of nanostructures.

Copyright © 2005 by American Society of Mechanical Engineers
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Figure 1

Schematic view of the diamond cubic structure on a cross section normal to the (111) surface. Shown is (a) the unreconstructed defect-free surface, (b) a surface vacancy, and two different types of adatoms (c) and (d).

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Figure 2

The strain effect on the driving force: (a) Si on Si, uniaxial strain εzz=0.005,r=3a0, always repulsion, and (b) Si on Si, uniaxial strain εzz=0.02,r=3a0

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Figure 3

The interaction between Si adatom and vacancy under large uniaxial strain

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Figure 4

Configuration to illustrate defect orientation and driving forces

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Figure 5

Vacancy-vacancy interaction

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Figure 6

Adatom-adatom interaction

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Figure 7

Adatom-vacancy interaction

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Figure 8

Comparison of far- and near-field under separation 2a0

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Figure 9

Molecular dynamics simulation of adatoms’ alignment under applied strain

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Figure 10

Molecular dynamics simulation illustrating the growth of a cluster




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