Edge-Trimmed Nanogaps in 2D Materials for Robust, Scalable, and Tunable Lateral Tunnel Junctions

Hai-Thai Nguyen,Yen Nguyen,Ya-Ping Hsieh,Mario Hofmann,Yen-Hsun Su

doi:10.3390/nano11040981

Abstract

Lateral tunnel junctions are fundamental building blocks for molecular electronics and novel sensors, but current fabrication approaches achieve device yields below 10%, which limits their appeal for circuit integration and large-scale application. We here demonstrate a new approach to reliably form nanometer-sized gaps between electrodes with high precision and unprecedented control. This advance in nanogap production is enabled by the unique properties of 2D materials-based contacts. The large difference in reactivity of 2D materials’ edges compared to their basal plane results in a sequential removal of atoms from the contact perimeter. The resulting trimming of exposed graphene edges in a remote hydrogen plasma proceeds at speeds of less than 1 nm per minute, permitting accurate control of the nanogap dimension through the etching process. Carrier transport measurements reveal the high quality of the nanogap, thus-produced tunnel junctions with a 97% yield rate, which represents a tenfold increase in productivity compared to previous reports. Moreover, 70% of tunnel junctions fall within a nanogap range of only 0.5 nm, representing an unprecedented uniformity in dimension. The presented edge-trimming approach enables the conformal narrowing of gaps and produces novel one-dimensional nano-trench geometries that can sustain larger tunneling currents than conventional 0D nano-junctions. Finally, the potential of our approach for future electronics was demonstrated by the realization of an atom-based memory.

Highlights

Carrier transport through atomically thin barriers proceeds by quantum mechanical tunneling, and the dependence of the tunneling current on barrier dimension and electrostatics are the foundation for scanning tunneling microscopes [1], tunneling diodes [2], Josephson junctions [3], etc
We present a novel approach to producing atomic-scale nanogaps by combining bottom-up and top-down patterning approaches
Atomic force microscopy (AFM) is an established technique to study nanostructures, but it cannot image the edge of the contact as the lateral extend of the AFM tip is larger than the nanogap

Summary

Introduction

Carrier transport through atomically thin barriers proceeds by quantum mechanical tunneling, and the dependence of the tunneling current on barrier dimension and electrostatics are the foundation for scanning tunneling microscopes [1], tunneling diodes [2], Josephson junctions [3], etc. The application of molecules as a barrier between two electrodes permits both the fundamental investigations of carrier transport and the realization of sophisticated molecular electronic devices [4,5,6,7]. To realize electrodes with atomic-scale lateral gaps, different strategies have been reported. The most commonly employed approach to producing lateral nanogaps are mechanically controlled break junctions(MBJs), where mechanical strain is employed to fracture an electrode at a predetermined position [13]

Methods

Results

Conclusion