Electronic structure of the diamond (111) 1×1 surface: Valence-band structure, band bending, and band gap states

Photoemission, LEED, and AES measurements were made on the mechanically polished (111) surface of a type IIa diamond. No emission from filled states in the fundamental gap was found over the photon energy range 13.3 eV?h/ω?200 eV. This result, coupled with the sharp 1×1 LEED patterns which were obtained and the relative cleanliness (of elements which can be detected by AES) of the diamond (≲1 at.% oxygen, 0.5 at.% Si) suggests hydrogen termination of the lattice. Photoelectric yield measurements demonstrate the photoelectric threshold to be at band gap energy radiation. Investigation of the photoemission electron distribution curves (EDC’s) shows that, while the electron affinity at the surface is always positive, band bending is sufficient to result in an effective negative electron affinity under certain conditions. A variable surface dipole on the atomic scale, possibly due to the adsorption–desorption of a background gas, is reported. A study of the relative cross section of the upper (p-like) versus the lower (s-like) portion of the diamond valence band indicates comparable cross sections at a photon energy h/ω=160 eV.