The process is shown in the figure above. First, nickel thin films are thermally evaporated on polyethylene naphthalate (PEN) substrates. Then the fabricated nickel/PEN films are sandwiched between two polymethyl methacrylate (PMMA) resins and the edge of the PMMA/nickel/PEN/PMMA structure is polished by chemical mechanical polishing (CMP) methods. Finally, the two sets of polished PMMA/nickel/PEN/PMMA structures are attached to each other with their edges crossing.

Cross-sectional TEM images of the nickel/PEN films show that there is no diffusion of nickel into the PEN layer and reveal a clear and smooth nickel/PEN interface. Here the nickel thickness is 17 nm, which gives a junction area of 17 × 17 nm2.

The ohmic I-V characteristics of the nickel-nickel nanojunction show good quantitative agreement with calculated results within the framework of a modified Anderson model. The analysis also predicts a high switching ratio in excess of 100,000:1 for nickel/molecule/nickel nanoscale junctions, which indicates that these junctions could have potential applications in novel switching devices.

Thus, the nanostructure fabrication method using thin-film edges, proposed in this study, is an important technology in terms of not only exceeding the limitations of conventional lithography but also in helping to create new switching devices with an ultrahigh on/off ratio.

The researchers presented their work in the journal Nanotechnology.