Electrical conduction in polycrystalline diamond and the effects of UV irradiation

Two band-gap states are identified in polycrystalline diamond films; a level at about 1.1 eV (density of 10(17) cm(-3), probably an acceptor state) and a trap level at about 1.9 eV (capture cross-section of 3+/-1 x 10(-17) m(2), probably a donor level). The level at 1.1eV governs the dark conduction which is consistent with a Poole-Frenkel conduction with overlapping states. Persistent photoconductivity and space-charge limited currents are observed after UV illumination. UV irradiation also gives rise to thermally stimulated currents related to the trap level at 1.9 eV. The occurrence of thermally stimulated currents can find application in radiation dosimetry, for which polycrystalline diamond films appear very promising. (C) 1997 Elsevier Science S.A.