Intrinsic luminescence blinking from plasmonic nanojunctions

Wen Chen,Aqeel Ahmed,Huatian Hu,Magalí Lingenfelder,Philippe Roelli,Sachin Verlekar,Tobias J Kippenberg,Karla Banjac,Giulia Tagliabue,Christophe Galland

doi:10.1038/s41467-021-22679-y

Wen Chen, Aqeel Ahmed + Show 8 more

Open Access

https://doi.org/10.1038/s41467-021-22679-y

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Abstract

Plasmonic nanojunctions, consisting of adjacent metal structures with nanometre gaps, can support localised plasmon resonances that boost light matter interactions and concentrate electromagnetic fields at the nanoscale. In this regime, the optical response of the system is governed by poorly understood dynamical phenomena at the frontier between the bulk, molecular and atomic scales. Here, we report ubiquitous spectral fluctuations in the intrinsic light emission from photo-excited gold nanojunctions, which we attribute to the light-induced formation of domain boundaries and quantum-confined emitters inside the noble metal. Our data suggest that photoexcited carriers and gold adatom - molecule interactions play key roles in triggering luminescence blinking. Surprisingly, this internal restructuring of the metal has no measurable impact on the Raman signal and scattering spectrum of the plasmonic cavity. Our findings demonstrate that metal luminescence offers a valuable proxy to investigate atomic fluctuations in plasmonic cavities, complementary to other optical and electrical techniques.

Highlights

Plasmonic nanojunctions, consisting of adjacent metal structures with nanometre gaps, can support localised plasmon resonances that boost light matter interactions and concentrate electromagnetic fields at the nanoscale
Illustrating the emerging opportunities in this field, the efficiency of intrinsic light emission from a noble metal under optical or electrical pumping can be enhanced by many orders of magnitudes thanks to the giant Purcell factor provided by plasmonic nanocavities[26,27,28,29,30,31]
While we cannot totally exclude the role of near-field optical forces acting within the nanojunction[17,53], this observation points to the key contribution of photo-excited electron–hole pairs in inducing the lattice restructuring, since 532 nm is close to the onset of interband absorption in gold

Summary

Introduction

Plasmonic nanojunctions, consisting of adjacent metal structures with nanometre gaps, can support localised plasmon resonances that boost light matter interactions and concentrate electromagnetic fields at the nanoscale. This latter process, which results in a fluctuating (i.e. blinking) luminescence and is the focus of our study, has its origin at the atomic scale, but is made observable thanks to the Purcell effect provided by the plasmonic modes of the entire junction.

Results

Conclusion