Atomistics of the epitaxial growth of Cu on W(110)

Abstract

Time-resolved in situ STM has been used to study the epitaxial growth of Cu on W(110) at temperatures ranging from room temperature up to 300°C. Sequences of STM images directly show the atomistics of the growth process on the surface. Additionally, SPA-LEED has been used to obtain precise information about the lateral geometrical dimensions of the different developing Cu structures. A sequence of three different structures is needed to transfer the Cu film to its intrinsic fcc-like behavior. The first layer of Cu on W(110) grows pseudomorphically in a fractal geometry. According to this growth behavior strain effects are considered to play a predominant role. With the second Cu layer a strained structure originates which is divided into small domains by a periodic trench network. A structure model for this double layer is suggested. Depending on the deposition conditions the trench network is decorated by a complex chain structure of third layer islands. Beginning with the completion of the third layer a periodic dislocation network appears. This structure can be attributed to an fcc Cu(111) layer with a slightly expanded surface unit mesh. Beyond the fourth layer a Cu on Cu(111) growth is established, which is only slightly affected by the underlying transition layer. Higher temperature deposits show an incomplete triple layer with a nearly perfect chain structure indicating that a relaxed third layer is metastable. Cu in excess grows in wedge-shaped 3D Stranski–Krastanov islands with atomically smooth (111) surfaces even on a misoriented substrate.