Bulk electronic structure of silicon studied with angle-resolved photoemission from the Si(100)2×1 surface

The bulk band structure of silicon along the Δ symmetry line in the Brillouin zone has been studied with polarization-dependent angle-resolved photoemission from the Si(100)2×1 surface. Normal-emission photoelectron spectra were recorded in the photon-energy range 7–30 eV. Bulk direct transitions from the three uppermost valence bands to four different final bands are identified in the spectra. The experimental final bands are in good agreement with calculated conduction bands from a linearized augmented-plane-wave calculation. The experimental energies of the ${\mathrm{X}}_4$, ${\mathrm{\Gamma }}_{12}^{\prime }$, and ${\mathrm{\Gamma }}_2^{\prime }$ critical points were found to be -3.1±0.2, 8.5±0.3, and 15.8±0.5 eV, respectively. For further comparison between experiment and theory, normal-emission photoelectron spectra were calculated based on the three-step model. Most of the structures in the theoretical spectra are identified also in the experimental spectra. Apart from the direct transitions, also peaks due to nondirect and surface-umklapp scattered transitions were found in the experimental spectra, originating from k points with a high density of states, near the X and L symmetry points. At low photon energies a dispersive peak was also found, which could not be assigned to an allowed final band in the theoretical band structure for normal emission.