Using ultra-violet and X-ray photo-electron spectroscopy, an investigation was made of four types of the (100) surface of homo-epitaxial diamond films; either doped with boron or undoped. Measurements were made of the position of the valence band maximum at the surface, the electronic affinity and the density of states. In p-type doped films, conductivity measurements indicated that the bulk Fermi level was pinned close to 0.4eV above the valence band edge and subtracting this value from the valence band maximum at the surface permitted the derivation of the band bending. The different (100) surfaces of the p-type diamond samples were (i) hydrogenated with the 2 x 1 reconstruction (H-surface), (ii) free with the 2 x 1 reconstruction, and either (iii) post-oxygenated or (iv) oxygenated during the growth, both with the 1 x 1 reconstruction (O-surface). All these surfaces exhibited a downward band bending, which implies hole depletion, ranging from 0.3eV for the H-surface to 1.2eV for the O-surface. Only the H-surface exhibited a negative electronic affinity (−0.9eV) whereas the others display positive electronic affinities in the range 0.9–2.2eV. Oxygen passivated the diamond surface, giving both very low conductivity and density of states in the band-gap, and increasing the band bending.

Band Bending, Electronic Affinity and Density of States at Several (100) Surfaces of Boron-Doped Homoepitaxial Diamond Thin Films. P.Muret, C.Saby: Semiconductor Science and Technology, 2004, 19[1], 1-7