Massively parallel fabrication of crack-defined gold break junctions featuring sub-3 nm gaps for molecular devices

Abstract

Break junctions provide tip-shaped contact electrodes that are fundamental components of nano and molecular electronics. However, the fabrication of break junctions remains notoriously time-consuming and difficult to parallelize. Here we demonstrate true parallel fabrication of gold break junctions featuring sub-3 nm gaps on the wafer-scale, by relying on a novel self-breaking mechanism based on controlled crack formation in notched bridge structures. We achieve fabrication densities as high as 7 million junctions per cm2, with fabrication yields of around 7% for obtaining crack-defined break junctions with sub-3 nm gaps of fixed gap width that exhibit electron tunneling. We also form molecular junctions using dithiol-terminated oligo(phenylene ethynylene) (OPE3) to demonstrate the feasibility of our approach for electrical probing of molecules down to liquid helium temperatures. Our technology opens a whole new range of experimental opportunities for nano and molecular electronics applications, by enabling very large-scale fabrication of solid-state break junctions.

Sub‐5 nm Metal Nanogaps: Physical Properties, Fabrication Methods, and Device Applications

“…In addition, as shown in Table , only a few methods can be used to fabricate multiple nanogap devices in a parallel manner. However, the production yields of nanogaps with the desired width are still very low, although the fabrication densities of nanogaps have reached a high level. In the application aspect, the nanogaps fabricated by physical methods can be used in various regimes ranging from molecular electronics to sensing and optical devices, whereas the sub‐5 nm nanogaps formed by nanoparticles are mostly limited to the regime of sensing and biomedicine devices based on the SERS technique.…”

“…Magnified SEM image of one sub‐3 nm nanogap. Reproduced with permission . Copyright 2018, Springer Nature.…”

“…However, TiN is brittle, and its conductivity is much lower than that of metal, limiting its application in electronic devices. Recently, their group introduced a true parallel fabrication method for gold break junctions with sub‐3 nm gaps on the wafer scale by relying on a self‐breaking mechanism based on controlled crack formation in notched bridge structures . The fabrication densities were reported to be as high as 7 million junctions cm −2 , with fabrication yields for sub‐3 nm junctions of ≈7%.…”

“…Furthermore, in recent years, insertion of an ultrathin layer has proven to be a promising technical strategy for creating sub‐5 nm nanogaps with wafer‐scale throughput via atomic layer deposition (ALD) or 2D materials with a precise control of the gap width . Another noteworthy fabrication method for sub‐5 nm nanogaps produces the so‐called breaking‐/cracking‐defined nanogaps, formed by imposing external stimuli, such as an electric current, a mechanical force, or a strain, has been widely employed in single‐molecule devices …”

2D Percolation Design with Conductive Microparticles for Low‐Strain Detection in a Stretchable Sensor

“…There have been several experimental reports about R tunnel . R tunnel was reported to be about 10 5 Ω when the gap distance was about 3 nm39 and no tunneling took place when the gap distance was larger than 5 nm 40. The small gap distance (≈5 nm) can be reached even at a small applied strain in this study (ε < 0.002), which is a negligible strain in the sensor.…”