It was noted that, when a (001) substrate was heated by passing a direct current through it, electromigration of the Si atoms occurred. The activation energies for Si migration (table 112) on the surface were investigated here by means of reflection electron microscopy. During growth of the 2 x 1 terrace, Si atoms were released from Sb substrate steps in the step-up direction. The activation energy was deduced to be about 1.60eV. During growth of the 1 x 2 terrace, Si atoms were released from Sa substrate steps, in the step-down direction, and the activation energy was equal to about 1.52eV. The front edge of the 2 x 1 terrace was the Sa step that was parallel to the dimer and the front edge of the 1 x 2 terrace was the Sb step that was perpendicular to it. In the case of electromigration, the difference in activation energies was attributed to a difference in the release energies from steps. The release energy of Si atoms from the Sb step in the step-up direction was about 0.08eV higher than the energy for their release from the Sa step in the step-down direction. The Si atoms were easily released from steps in the step-down direction on the surface. There was also a difference in the frequency factors. The frequency factor for Sb steps in the step-up direction was about twice as high as the frequency factor for Sa steps in the step-down direction.

Anisotropic Diffusion between the Step-Up and the Step-Down Directions on a Si(001) Surface. T.Doi, M.Ichikawa, S.Hosoki, K.Ninomiya: Physical Review B, 1996, 53[24], 16609-14