STEP STRUCTURE TRANSFORMATION OF SI(001) SURFACE INDUCED BY CURRENT

The domain conversion mechanism on a Si(001) surface induced by DC current is investigated, and the origin of the critical step spacing is clarified. The conversion between 2 x 1 and 1 x 2 domains on the Si(001) surface proceeds with the movement of each step, caused by the transport of adatoms across the terrace. The uniform driving force on adatoms is assumed to be induced by the supply of DC current. The step kinetics is treated by developing the BCF (Burton, Cabrera and Frank) theory to take account of the three effects: contribution of the drift flux of adatoms, anisotropy of a diffusion constant, and repulsive interaction between steps. The domain conversion is induced by the coupling of the first and second effects. The balance condition between the drift flux and the backward diffusion flux caused by the repulsive step-step interaction determines the critical spacing. The time evolution of step configuration is calculated numerically, and it explains well the observed behaviour.