ELECTRICAL MEASUREMENTS OF BETA-COBALT PHTHALOCYANINE SINGLE-CRYSTALS

A detailed study of current as a function of voltage at different temp eratures, coupled with that of the dependence of current on sample thi ckness at a given voltage and temperature has been made in the C-direc tion of beta-cobalt phthalocyanine (beta-CoPc) single crystals using g old electrodes. Results show that at low voltages the conduction proce ss is ohmic, while at high voltages space-charge-limited conduction is present. Traps with a density of 5.2 x 10(25) m(-3) located at 0.34 e V above the valence band edge have been observed. The voltage at which the transition from ohmic to space-charge-limited behaviour takes pla ce has been found to be independent of the temperature. The results ar e interpreted in terms of the extrinsic nature; of ohmic conduction in beta-CoPc single crystals, The thickness dependence in the square-law region has been found to confirm the L(-3) law.