Fabrication of nickel/organic-molecule/nickel nanoscale junctions utilizing thin-film edges and their structural and electrical properties

Metal/organic-molecule/metal nanoscale junctions, which consist of poly(3-hexylthiophene):6,6-phenyl C61-butyric acid methyl ester (P3HT:PCBM) organic molecules sandwiched between two Ni thin films whose edges are crossed, which are called quantum cross (QC) devices, have been fabricated and their structural and electrical properties have been investigated. The area of the crossed section, which was obtained without using electron-beam or optical lithography, can be as small as 16 × 16nm ². We have obtained ohmic current-voltage characteristics, which show quantitative agreement with the theoretical calculation results performed within the framework of the Anderson model under the strong coupling limit. Calculation results also predict that a high on-off ratio beyond 100000 : 1 can be obtained in Ni/P3HT:PCBM/Ni QC devices under the weak coupling condition. These results indicate that our method utilizing thin-film edges is useful for creating nanoscale junctions and Ni/P3HT:PCBM/Ni QC devices can be expected to have potential application in next-generation switching devices with high on-off ratios.