Surface electronic structure of Si1-xGex(001)-2 x 1: a synchrotron radiation photoemission study

By using synchrotron radiation photoemission, this study investigates the room-temperature surface electronic structure of Si1-xGex(001)-2 x 1 grown by molecular-beam epitaxy on anepiGe(001) substrate. The electronic structure of the Ge content, which ranges from 10% to 90%, shows similar surface behaviors. The Ge 3d core-level spectra of Si1-xGex(001)-2 x 1 are essentially the same as that ofepiGe(001)-2 x 1, terminating with tilted Ge-Ge dimers and Ge atoms in the subsurface layer. The strain effect is manifest only for the Si atoms, for which three types are revealed, namely two near the surface region and one in the bulk.