A research team led by Prof. YANG Liangbao from Hefei Institutes of Physical Science, Chinese Academy of Sciences found that hexagonal boron nitride (h-BN) could effectively block electron tunneling and extend the ultimate plasmonic enhancement limits in a single-atom-layer gap, providing deep insights into quantum mechanical effects in plasmonic systems and enabling potential novel applications based on quantum plasmonics.
The results were published in Nano Letters.
The team have been working on developing surface-enhanced Raman spectroscopy (SERS) detection methods for years and found that the near-field intensity distribution in the nanometer scale is uneven. To achieve greater electromagnetic enhancement, they used adjacent metal nano-gaps but noticed that reducing their size leads to the emergence of quantum tunneling effect, making it disadvantageous for SERS detection.
To overcome this, the team introduced a high tunneling barrier formed by monolayer h-BN, actively blocking the electron tunneling effect. They quantitatively detected the final near-field enhancement limit in the classical framework by detecting the intrinsic SERS intensity of h-BN in a single particle cavity.
The study proved that monolayer h-BN blocks the electron tunneling using hot electron tunneling quantum computation and layer-dependent scattering spectrum experiments. By comparing the experimental results with the calculated results of the classical electromagnetic model and the quantum correction model, the team realized the final near-field enhancement limit detection within the classical framework.
This work provides important guidance for quantum plasmology and nano-gap photodynamics, helping to further analyze quantum mechanical effects in plasma enhancement. These findings are published in the top international journal Nano Letters and selected as the cover of the current issue.
The paper was selected for front cover of Nano Letters. (Image by CHEN Siyu)
(left) Schematic of a monolayer h-BN as hot-electron tunneling barrier.(right) Change of volume-averaged SERS enhancement factor (EF) with the gap size (e.g., number of h-BN layers). (Image by CHEN Siyu)
