Electron trapping and bulk conduction in β-form metal-free phthalocyanine single crystals in vacuum

Abstract Experimental evidence is given showing that for a vacuum ambient of 5 × 10 −9 Torr (1) the current in the square-law region is indeed space charge limited (2), 10 19 −10 20 cm −3 trapping centers exist 0.38 eV below the conduction-band edge, and (3) below 90°C the ohmic conduction is extrinsic due to the presence of 10 12 −10 13 cm −3 donors at the trapping level.