Atomic structure analysis of the interfaces inSi/Ge superlattices

Using medium-energy ion scattering, we have studied interface structures between Si and Ge thin layers in GenSim strained-layer superlattices (SLSs) grown by molecular beam epitaxy. In this systems, the horizontal strain caused by lattice mismatch, further causes vertical atomic displacement. The embedded Ge layers are compressed horizontally and expanded vertically compared with the ideal cubic crystal. Since the interfaces of Si layers grown onto Ge layers in SLS are not so abrupt at the atomic scale because of the Ge segregation effect, Ge atoms at the interfaces are displaced not only vertically but also laterally. We observed a peculiar blocking dip, which is explained by an interfacial structure characterized as alternate Si and Ge arrangement forming a2 × n periodicity.