Photoemission studies of 74Ge+ implantation synthesized Si1−xGex amorphous alloys

Si(100) crystals were ion implanted by 74Ge+ to synthesize Si1−xGex alloys with x=0.5 and 5.0%. The as-implanted layers were identified as amorphous by means of electron diffraction, and the valence band density of states was measured by UV-photoemission. The spectra were found to depend strongly on the Ge concentration, and were very different from the previously reported data on amorphous Si. The modifications are tentatively interpreted in terms of rehybridization of the sp3 bonds, in analogy with the well-known sp3–sp2 transition in carbon.