Fabrication of 5 nm gap pillar electrodes by electron-beam Pt deposition

Using a focused ion beam (FIB)-scanning electron microscope (SEM) workstation, free-standing nanoelectrodes were grown by SEM-assisted Pt deposition between FIB-patterned Au pads. Two pillar electrodes were first grown with opposite-tilted geometries up to a spacing of 120 nm. By SEM scanning over the pillar tips, under a precursor gas flow, gap reduction down to 5 nm was monitored in live imaging mode. As shown by transmission electron microscopy (TEM) analysis, the deposit consisted of Pt crystallites embedded in amorphous- C. Local annealing by high-current TEM irradiation increased the size of the Pt grains, which produced clear diffraction rings. The annealing procedure did not affect the overall shape of the tips, indicating good mechanical stability of the pillars. We show how this FIB-SEM approach is suitable to fabricate multielectrode nanostructures by depositing a third pillar electrode below the gap of the tilted electrodes.