Large area single crystal gold of single nanometer thickness for nanophotonics

Two-dimensional single crystal metals are highly sought after for next-generation technologies. This paper reports the fabrication of large-area (>10⁴ μm²), single-crystal two-dimensional gold flakes (2DGFs) with thicknesses down to a single nanometer, using an atomic-level precision chemical etching approach. The ultrathin 2DGFs exhibit quantum-confinement-augmented optical nonlinearity, showing more than two orders of magnitude enhancement in harmonic generation compared to thicker polycrystalline counterparts. Their single-crystal quality and nanometer-scale thickness make them a promising platform for plasmonic nanostructures, as demonstrated by patterning them into nanoribbon arrays with strongly confined near-infrared plasmonic resonances and high quality factors. The 2DGFs offer a new platform for nanophotonic research and applications in ultrathin plasmonic, optoelectronic, and quantum devices.

Chenxinyu Pan, Yuanbiao Tong, Haoliang Qian, Alexey V. Krasavin, Jialin Li, Jiajie Zhu, Yiyun Zhang, Bowen Cui, Zhiyong Li, Chenming Wu, Lufang Liu, Linjun Li, Xin Guo, Anatoly V. Zayats, Limin Tong, Pan Wang