Fig. 4
Classifying junctions using electrical characterization and SEM imaging. a Schematic of two probe electrical characterization, and b the collected results of the electrical characterization of 86 nominally identical junctions featuring an initial bridge length of L = 3.3 µm and a 90 nm wide constriction. Due to the stochastic breaking of the strained gold at the crack-lines of each of the 86 junctions, the resulting gold electrodes were either connected by one or two unbroken ligaments of total resistance R, or separated by gaps of widths d. Of the 86 junctions, 33 junctions showed ohmic behavior with at least one connected ligament, 46 junctions showed electrically isolated electrodes which could also be confirmed by visual inspection, and seven junctions showed tunneling I–V characteristics thereby revealing gold ligaments that have broken and formed a sub-3 nm gap. c–e Representative I-V characteristics of the three outcomes: ohmic, tunneling and isolated. f–n SEM images of three representative probed junctions for each of the three outcomes: ohmic (f–h), tunneling (i–k), and isolated (l–n) are shown. These SEM images illustrate the strong correlation found between the electrical characterization performed ‘blind’, without prior visual inspection of the junctions, and the morphology of the junctions revealed by SEM imaging. Scale bar is 200 nm for f–n and 100 nm for insets of f–n
