Nonlinear Effect in Step Bunching Caused by Electric Current

Abstract

We study nonlinear effects in step bunchingin a surface diffusion field with a directelectric current.Linear stability analysis showsthat the bunching instability occursin sublimation at long wavelength if the step distance is smaller than the surface diffusion lengthand the drift of adatoms induced by the electric currentis in the step down direction.When we take account of the nonlinear effect, the density of steps obeys the Benney equation, which shows an array of step bunches or spatiotemporal chaos.This feature is similar to the step bunching causedby the asymmetry of step kineticsexcept that the surface profile may change withthe sign of the dispersion term.