Electronic structure of Ge(111) and Ge(111): H from angle-resolved-photoemission measurements

Angle-resolved-photoemission measurements were made on the annealed (111) surface of germanium and on the same surface with adsorbed hydrogen. Spectra are presented for various values of {k}_, the wave-vector component parallel to the surface, for the 110 and 112 directions, and for photon energies of 16. 85 and 21. 22 eV. Two surface states at 0. 8 and 1. 4 eV below the top of the valence band were found in the spectra for the reconstructed Ge (111) - (8) surface. Both states showed only small changes in energy as a function of {k}_ but distinct intensity variations. Bulklike states were also found and are compared to E ({k}_) curves calculated with a pseudopotential method. The addition of hydrogen to the surface removed the reconstruction and drastically altered the photoemission spectra. A strong hydrogen-induced peak at an average binding energy of about 5 eV showed a similar dispersion to that calculated for Si (111): H by Pandey.