Large-Scale Sub-1-nm Random Gaps Approaching the Quantum Upper Limit for Quantitative Chemical Sensing

Nan Zhang, Haifeng Hu, Matthew Singer, Kuang-hui Li, Lyu Zhou, Boon S. Ooi, Qiaoqiang Gan

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


Metallic nanostructures with nanogap features can confine electromagnetic fields into extremely small volumes. In particular, as the gap size is scaled down to sub-nanometer regime, the quantum effects for localized field enhancement reveal the ultimate capability for light–matter interaction. Although the enhancement factor approaching the quantum upper limit has been reported, the grand challenge for surface-enhanced vibrational spectroscopic sensing remains in the inherent randomness, preventing uniformly distributed localized fields over large areas. Herein, a strategy to fabricate high-density random metallic nanopatterns with accurately controlled nanogaps, defined by atomic-layer-deposition and self-assembled-monolayer processes, is reported. As the gap size approaches the quantum regime of ≈0.78 nm, its potential for quantitative sensing, based on a record-high uniformity with the relative standard deviation of 4.3% over a large area of 22 mm × 60 mm, is demonstrated. This superior feature paves the way towards more affordable and quantitative sensing using quantum-limit-approaching nanogap structures.
Original languageEnglish (US)
Pages (from-to)2001634
JournalAdvanced Optical Materials
StatePublished - Oct 28 2020

Bibliographical note

KAUST Repository Item: Exported on 2020-11-02
Acknowledgements: This work was partially supported by NSF CMMI-1562057 and ECCS-1807463. The authors appreciate Dr. Lingmei Liu and Prof. Yu Han at KAUST for helpful suggestions on TEM characterization.


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