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Length Scales in Step-Bunch Self-Organization during Annealing of Patterned Vicinal Si(111) Surfaces

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Length Scales in Step-Bunch Self-Organization during Annealing of Patterned Vicinal Si(111) Surfaces

Professor Raymond Phaneuf

University of Maryland


Abstract:   Using lithographic patterning and high-temperature annealing we investigate the length-scale dependence of self-organization of step-bunches on vicinal Si(111) surfaces. Sublimation and diffusion result in the motion and interference of misorientation-derived straight steps and the circular steps which bound cylindrical pits. Annealing of patterns with small pit diameters produces a rapid relaxation to straight step-bunches, while larger structures maintain significant in-plane corrugations for as long as the out-of-plane corrugations persist; these two types of behavior are separated by an extended transitional regime . We simulations of the evolution using the mesoscopic model proposed by Weeks, et al [1] to describe the motion of individual steps under the effects of sublimation, step stiffness (line tension), and step-step interaction. The qualitative consistency between our simulation and experiment [2] suggest that thermodynamic driving force, such as the step-stiffness and step-step interaction dominate the evolution of the step structure during high temperature annealing. We are also able to explain the characteristic length scales separating the three regimes of relaxation based upon simple arguments based upon a competition between terms which drive step velocity.

[1] J. D. Weeks, D.-J. Lui, and H.-C. Jeong, in Dynamics of Crystal Surfaces and Interfaces, edited by P. M. Duxbury and T.J. Pence (Plenum Press, New York and London 1997), pp. 199-216
[2] T. Kwon, H-C. Kan, R. J. Phaneuf, Appl. Phys. Lett. 88, 071914 (2006)

*Work supported by the Laboratory for Physical Sciences and by the NSF-MRSEC at the University of Maryland, DMR 0520471
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