ELECTRICAL AND PHOTOCONDUCTIVE PROPERTIES OF ORIENTATION-CONTROLLED CHLOROALUMINUMPHTHALOCYANINE THIN-FILMS

Structure dependence of electrical properties was investigated for amo rphous and epitaxial thin films of chloroaluminumphthalocyanine vacuum deposited on both glass and KCl. The extrinsic conductivity in the da rk was improved by elevating substrate temperatures, depending on the morphological change from granular, discontinuous films deposited at a substrate temperature of 25-degrees-C to uniform, continuous ones at 250-degrees-C. The photocurrents under monochromatic light illuminatio n increased in proportion to the amount of adsorbed O2 in the amorphou s films on glass. A regular doping form of O2 in the epitaxial film on KCl could enhance photocarrier generation. The granular, discontinuou s morphology in the films caused a frequent charge-carrier recombinati on at the grain boundaries and defect sites. In the intrinsic region t he amorphous films exhibited a higher dark conductivity due to the pi- electron interaction between the randomly arranged molecules and gave a moderate activation energy for conduction. The epitaxial film with a regular orientation exhibited a significantly higher activation energ y for intrinsic dark conduction because of a weak molecular interactio n between the standing molecular columns.