Tunneling images of germanium surface reconstructions and phase boundaries

We have imaged with the tunneling microscope the microscopic surface topography of germanium layers grown by molecular-beam epitaxy on Si(111)-7×7. The surface structures corresponding to Ge(111)-c2×8 and Ge(111)-7×7 are resolved. The Ge-c2×8 structure is shown to consist of a coherent combination of two simpler units both of which exist independently on the surface. The associated phase boundaries are illustrated. The Ge 7×7 structure is shown to be similar to that obtained for Si(111). Defects in the cell are also imaged. © 1985 The American Physical Society.