STM studies of the growth of the Si/Cu(110) surface alloy

The stages of the growth of the surface alloy c(2 x 2)-Si/Cu(110) have been analysed on the basis of scanning tunneling microscopy images and low electron energy diffraction (LEED) patterns. The formation of this interface goes through several stages as the Si coverage is increased. For a Si coverage ca 0.1 monolayer (ML), structured islands are observed on the surface. They are aligned along the [(1) over bar 12] surface direction which corresponds to the Si-Si bonding direction in the atomic model. These islands grow and coalesce upon Si coverage, forming extended alloy areas. Defects, consisting of grouped atomic vacancies, along the [(1) over bar 10] surface direction are observed at this stage of growth which are reflected on the corresponding LEED pattern as diffuse c(2 x 2) spots enlarged along the [001] surface direction. Complete and free of defects alloy terraces are observed for a Si coverage ca 0.5 ML, that is, when the completion of the overlayer alloy is attained. Atomic resolution STM images show a c(2 x 2) atomic arrangement which can be explained as a near coplanar substitution of Cu by Si atoms. Throughout the text the relationship between the growth stages and the perfection of the alloy layer is discussed. (C) 1998 Elsevier Science B.V. All rights reserved.