Band Engineering In An Epitaxial Two-Dimensional Honeycomb Si6-Xgex Alloy

In this Letter, we demonstrate that it is possible to form a two-dimensional (2D) silicenelike Si5Ge compound by replacing the Si atoms occupying on-top sites in the planarlike structure of epitaxial silicene on ZrB2 (0001) by deposited Ge atoms. For coverages below 1/6 monolayer, the Ge deposition gives rise to a Si6-xGex alloy (with x between 0 and 1) in which the on-top sites are randomly occupied by Si or Ge atoms. The progressive increase of the valence band maximum with x observed experimentally originates from a selective charge transfer from Ge atoms to Si atoms. These achievements provide evidence for the possibility of engineering the band structure in 2D SiGe alloys in a way that is similar for their bulk counterpart.