NEA peak of the differently terminated and oriented diamond surfaces

The negative electron affinity (NEA) peak of differently terminated and oriented diamond surfaces is investigated by means of ultraviolet photoemission spectroscopy. Electron emission measurements in the range below the conduction band minimum (CBM) up to the vacuum level E-vac permit the quantitative calculation of the upper limit of the NEA value. The inelastic scattering at the surface to the vacuum interface and the emission of electrons from the unoccupied surface states, situated in the band gap, are the mechanisms responsible for explaining this below CBM emission. All the H-terminated diamond surfaces present NEA. However, the characteristic NEA peak observed in the spectra is only detected for the (100)-(2 x 1):H surface and to a lesser extent for the (110)-(1 x 1):H surface, while it is absent for the (111)-(1 x 1):H surface because of the k(parallel to)-conservation in the photoemission process. (C) 1999 Published by Elsevier Science B.V. All rights reserved.