Band diagram of diamond and diamond-like carbon surfaces

The electron affinity (EA) of various terminations of diamond surfaces has been calculated by the ab-initio pseudopotential method. The bare, reconstructed (100) and (111) surfaces are found to have positive EAs of 0.5 eV and 0.35 eV, respectively. The hydrogen-terminated surfaces 1 x 1(100):2H, 2 x 1(100):H and (111):H have sizeable negative EAs of orders -2.4 eV, -2.0 eV and -2.0 eV, respectively. Oxygen terminations give large postive EAs. The barrier height of a diamond/graphite Schottky barrier is found. These data are used to derive a band diagram for diamond and diamond-like carbon field emitters. The main barrier for electron emission from diamond is at the back contact, and nitrogen deep donors aid emission by creating a depletion layer that reduces the tunnelling distance. Diamond-like carbon has sizeable positive EAs, the main barrier is at the front surface, and nitrogen is a weak shallow donor that raises the Fermi level to lower the barrier. (C) 1998 Elsevier Science S.A.