A transmission electron microscopic study of the topography of clean Si(111) surfaces

Steps on Si(111) surfaces are shown to be preserved at the interfaces of epitaxial silicide layers grown at room temperature. Symmetry requires the formation of a dislocation at every step of this (type B) interface. This has enabled the examination, by transmission electron microscopy, of the topography of large areas of the Si surface after various treatments. Silicon molecular-beam epitaxy (MBE) is shown to occur via step-flow mechanism at high temperatures, and through nucleation and growth of islands on the terraces at low growth temperatures. These observations point to the importance of including nucleation mechanism into existing theories, especially at high supersaturation. A change of step character from 〈112̄〉to 〈∼(11) 2〉 at the initial stage of MBE is observed and is attributed to the stabilities of the two types of steps in relationship to the 7×7 structure. Preliminary results on vicinal Si(111) surfaces are also presented.