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Abstract:
Bearing Si(001) vicinal surfaces in mind [1,2], we study drift-induced bunching
and wandering of steps on a vicinal surface with anisotropic surface diffusion. The
direction of fast diffusion alternates on consecutive terraces and evaporation is neglected.
When drift of adatoms induced by an external electric field is perpendicular to
the steps, the vicinal face is unstable for pairing instability with both step-up and
step-down drift. By means of Monte Carlo simulation [3] and numerical integration
of a one-dimensional model, we study time development of step bunching. Large
bunches appear irrespective of the drift direction, and their average size
grows in a power low as N ∼ tα with α ≈ 1/2. The distance between steps in a
bunch is sensitive to the step interaction potential.
When step bunching is suppressed by
a strong step repulsion, step wandering
takes place with step-up drift. Repulsive
interaction between steps is found indispensable
for the instability. Monte Carlo
simulation shows that in-phase step wandering
produces straight grooves.
Nonlinear evolution equation for the step
pattern is the same as that of Si(111) vicinal
faces [4,5] although mechanisms for the
instabilities are very different. Grooves
widen slowly as their amplitudes increase
in proportion to the square root of time.
[1] A. V. Latyshev et al., Aseev, Appl. Surf.
Sci. 130, 98 (1998).
[2] J.-F. Nielsen et al., Surf. Sci. 480, 84
(2001).
[3] M. Sato et al,. J. Cryst. Growth 237-
239, 43 (2002).
[4] O. Pierre-Louis et al., Phys. Rev. Lett.
80, 4221 (1998).
[5] M. Sato et al., Phys. Rev. B 65, 245427
(2002).
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