High-Performance, Single-Crystal Gold Bowtie Nano-Antennas via Epitaxial Electroless Deposition

Material quality can play a critical role in the performance of nanometer-scale plasmonic structures. Here, we highlight a novel deposition strategy for single-crystal noble metal deposition and provide a direct and quantitative comparison between the fabrication yield, durability, and efficiency of bowtie nano-antennas fabricated from monocrystalline and polycrystalline gold films using subtractive nanofabrication. Focused ion beam milling of monocrystalline Au(100) films deposited through epitaxial electroless deposition to form bowtie nano-antennas produces devices that demonstrate key performance enhancements over devices patterned identically from polycrystalline Au films deposited via physical vapor deposition. Single-crystal bowties reveal significant improvements in pattern transfer fidelity and device yield, the ability to tailor and model local plasmonic field enhancements and marked improvement in their thermal and mechanical stability over those fabricated from polycrystalline Au films. This work underscores the performance advantages of single-crystal nanoscale plasmonic materials and describes a straightforward, solution-phase deposition pathway to achieve them. We anticipate that this approach will be broadly useful in applications where local near-fields can enhance light−matter interactions, including for the fabrication of optical sensors, photocatalytic structures, hot carrier-based devices, and nanostructured noble metal architectures targeting nano-attophysics.