Phys. Rev. Lett. 83, 5531-34 (1999).
Onset of Step Anti-Banding Instability due to Surface Electromigration
K. Thürmer, D-J. Liu, E. D. Williams, and J. D. Weeks
Heating by a direct electric current can produce step bunches
on vicinal semiconductor surfaces. Under extreme conditions, steps crossing
from one bunch to another bend sufficiently to create bands of steps of
the opposite sign (antibands). Unusual large scale STM-images reveal a
mechanism where field-induced concentration gradients produce a spatially
variable step velocity that drives the antiband formation. A continuum
step model allows quantitative analysis of crossing step shapes, yielding
an effective charge for the diffusing adatoms of qeff = 0.13 electron units
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