Surfactant epitaxy of Si on Si(111) mediated by Sn

Surfactant epitaxy is studied by high-resolution reflection electron microscopy for the growth of Si on a Si(111) surface covered by a tin (Sn) layer. The growths on stepped surfaces occur chiefly by the step flow at substrate temperatures above ≃330°C. The Si atoms deposited on the Sn layer diffuse underneath the Sn layer to be incorporated with the bulk Si layer, so that the Sn layer is always located at the outermost surface to maintain the step flow as well. The growths with and without the Sn layer are studied comparatively to find an approximate relation, λ c 2 ∼ A exp (- E / k T c ), between the critical step distance for the step flow, λ c , and the substrate temperature, T c . The step flow for the Si/Sn/Si occurs at much lower temperature and at much longer step distance than for the Si/Si: at 330°C, λ c ≃1240 nm for Si/Sn/Si, and λ c ≃175 nm for Si/Si.