Conduction-band and surface-state critical points in Si: An inverse-photoemission study

From measurements of the dispersion of the lowest two conduction bands in silicon by k-resolved inverse photoemission the energies of the L1c and L3c critical points were determined as 2.40±0.15 and 4.15±0.10 eV relative to the valence-band edge, respectively. A comparison with energies derived from photoemission and optical data reveals a large excitonic lowering of the E1 transition by 0.5±0.2 eV. The lowest unoccupied surface state on the Si(111) 2×1 surface at Γ̄ is identified at 1.2±0.1 eV. © 1985 The American Physical Society.