Growth of (√3 x √3)-Ag and (111) oriented Ag islands on Ge/Si(111) surfaces

We have studied the growth of Ag on Ge/Si(1 1 1) substrates. The Ge/Si(1 1 1) substrates were prepared by depositing one monolayer (ML) of Ge on Si(1 1 1)-(7 x 7) surfaces. Following Ge deposition the reflection high energy electron diffraction (RHEED) pattern changed to a (1 x 1) pattern. Ge as well as Ag deposition was carried out at 550 degrees C. Ag deposition on Ge/Si(1 1 1) substrates up to 10 ML has shown a prominent (root 3 x root 3)-R30 degrees RHEED pattern along with a streak structure from Ag(1 1 1) surface. Scanning electron microscopy (SEM) shows the formation of Ag islands along with a large fraction of open area, which presumably has the Ag-induced (root 3 x root 3)-R30 degrees structure on the Ge/Si(1 1 1) surface. X-ray diffraction (XRD) experiments show the presence of only (1 1 1) peak of Ag indicating epitaxial growth of Ag on Ge/Si(1 1 1) surfaces. The possibility of growing a strain-tuned (tensile to compressive) Ag(1 1 1) layer on Ge/Si(1 1 1) substrates is discussed. (C) 2009 Elsevier B.V. All rights reserved.