Large-area, freestanding single-crystal gold of single nanometer thickness

TL;DR

This paper reports the fabrication of large-area, single-crystal, ultrathin two-dimensional gold with unique optical, electrical, and mechanical properties, enabling new applications in optoelectronics, photonics, and quantum devices.

Contribution

It introduces a novel atomic-level-precision chemical etching method to produce large-area, freestanding single-crystal gold of single-nanometer thickness.

Findings

Achieved large-area (>10^4 μm²) single-crystal 2D gold

Demonstrated quantum-confinement-augmented optical nonlinearity

Observed high-quality near-infrared plasmonic resonances with Q factor up to 5

Abstract

Two-dimensional single-crystal metals are highly sought after for next-generation technologies. Here, we report large-area (>10^4 {\mu}m2), single-crystal two-dimensional gold with thicknesses down to a single-nanometer level, employing an atomic-level-precision chemical etching approach. The ultrathin thickness and single-crystal quality endow two-dimensional gold with unique properties including significantly quantum-confinement-augmented optical nonlinearity, low sheet resistance, high transparency and excellent mechanical flexibility. By patterning the two-dimensional gold into nanoribbon arrays, extremely-confined near-infrared plasmonic resonances are further demonstrated with quality factors up to 5. The freestanding nature of two-dimensional gold allows its straightforward manipulation and transfer-printing for integration with other structures. The developed two-dimensional gold provides an emerging platform for fundamental studies in various disciplines and opens up new opportunities for applications in high-performance ultrathin optoelectronic, photonic and quantum devices.