Nano-scale resistivity reduction in single-grain of lead phthalocyanine

Control of interfaces and boundaries of organic electronic materials are important issues in device applications. Methods to determine electrical transport in such regions on the nanometre-scale are limited, however. We developed top-contact nano-gap electrodes and point-contact current-imaging atomic force microscopy (PCI-AFM) to measure nanometre-scale electrical conduction of organic thin films with reduced damage at metal/organic interfaces. Using these nano-scale methods, in-plane space-charge limited conduction is observed for single-phase monoclinic lead phthalocyanine (PbPc) thin films at high electric field. Apparent film resistivity at low voltage is two orders of magnitude lower than that measured by conventional micro-scale methods. Nanometre-scale spatially-resolved current-analysis of single-domain monoclinic PbPc crystal reveals non-linear distance-resistance characteristics, resulting in a low distance-differential resistance of 10 Ωm. The technologies used here allow us to find intrinsic electrical properties of organic electronic materials and to clarify the influence of interfaces and boundaries, forming the basis of nano-scale organic electronics.