Extending the boundaries of plasmonic enhancement with hexagonal boron nitride

April 24, 2023

(Nanowerk News) A study pioneered by Professor Yang Liangbao of the Hefei Institutes of Physical Science at the Chinese Academy of Sciences found that hexagonal boron nitride (h-BN) effectively inhibits electron tunneling, thereby extending the limit of ultimate plasmonic enhancement in single-atomic layer gaps. This breakthrough offers valuable insights into quantum mechanical phenomena in plasmonic systems and paves the way for innovative applications in the field of quantum plasmonics.

The findings were published in a journal Nano Letters (“Extending the Limits of Plasmonic Enhancement by Tunneling Blocked Electrons by Monolayer Hexagonal Boron Nitride”). Schematic of a monolayer h-BN as a hot electron tunneling barrier (left); Convert the volume-average SERS increase factor to the gap size (eg, number of h-BN layers) (right). (Image: CHEN Siyu)

The team has dedicated years to developing a surface-enhanced Raman spectroscopy (SERS) detection technique, noting that the distribution of near-field intensity is not uniform at the nanoscale. To achieve higher electromagnetic enhancements, they used adjacent metal nanoslits but observed that decreasing their size resulted in the appearance of an unwanted quantum tunneling effect, which hindered SERS detection.

To overcome this problem, the researchers introduced a high tunneling barrier consisting of a monolayer of h-BN, which successfully blocks the electron tunneling effect. They then quantitatively quantified the limit of near-end field enhancement in the classical framework by assessing the h-BN intrinsic SERS intensity in the single particle cavity.

Investigations demonstrated that h-BN monolayers inhibit electron tunneling via hot electron tunneling quantum computing and layer-dependent scattering spectra experiments. By comparing the experimental data with the calculated results from the classical electromagnetic model and the quantum correction model, the team achieved detection of the ultimate near field enhancement limit in the classical framework.

This study offers important guidance for quantum plasmonics and nano-gap photodynamics, and contributes to a deeper understanding of the effects of quantum mechanics in plasmonic enhancement.

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