Thermal properties of anisotropic diffusion of Si adsorbates on a Si(001) surface

The diffusion of Si adsorbates deposited on a Si(001) clean surface is investigated by using a reflection electron microscope (REM), When the sample is heated by radiative heating and/or direct current heating, the denuded zones are created at the terrace edge, The diffusion constants of the Si adsorbates are determined based on the denuded zone width. Isotropic diffusions are observed in the opposite directions both on the 2 x 1 terrace and on the I x 2 terrace, Diffusion constants have the same Value in both the step-up and the step-down directions, so D-u(2 x 1) = D-d(2 x 1) = D-2 x 1 and D-u(1 x 2) = D-d(1 x 2) = D-1 x 2, at least up to 800 degrees C, However, the diffusion constant D-1 x 2 perpendicular to the dimer is 5 to 6 times as large as the diffusion constant D-2 x 1 parallel to it, thus anisotropic diffusion is observed on a Si(001) surface.