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

TL;DR

This paper presents a novel wafer-scale, parallel fabrication method for gold break junctions with sub-3 nm gaps, enabling large-scale production for molecular electronics with demonstrated molecular junctions.

Contribution

A new self-breaking technique based on controlled crack formation allows massively parallel fabrication of ultra-narrow gold break junctions on the wafer scale.

Findings

Achieved fabrication densities of 7 million junctions per cm².

Yield of around 7% for sub-3 nm gap junctions with electron tunneling.

Successfully formed molecular junctions with oligo(phenylene ethynylene).

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 cm$^{2}$, 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.