Effects of gap thickness and emitter location on the photoluminescence enhancement of monolayer MoS 2 in a plasmonic nanoparticle-film coupled system

Nanophotonics

article

Xiaozhuo Qi¹  Xifeng Ren¹  Tsz Wing Lo³  Di Liu¹  Lantian Feng¹  Yang Chen¹  Yunkun Wu¹  Hongliang Ren⁴  Guang-Can Guo¹  Dangyuan Lei⁵ 

[1] Key Laboratory of Quantum Information, University of Science and Technology of China;Synergetic Innovation Center of Quantum Information & Quantum Physics, University of Science and Technology of China;Department of Applied Physics, The Hong Kong Polytechnic University;College of Information Engineering, Zhejiang University of Technology;Department of Materials Science and Engineering, City University of Hong Kong

关键词: nanoparticle-film coupled system;    photoluminescence enhancement;    plasmonic nanocavity;    transition-metal dichalcogenides;   

DOI  :  10.1515/nanoph-2020-0178

学科分类：社会科学、人文和艺术（综合）

来源: De Gruyter

【 摘 要 】

Plasmonic nanocavities comprised of metal film-coupled nanoparticles have emerged as a versatile nanophotonic platform benefiting from their ultrasmall mode volume and large Purcell factors. In the weak-coupling regime, the particle-film gap thickness affects the photoluminescence (PL) of quantum emitters sandwiched therein. Here, we investigated the Purcell effect-enhanced PL of monolayer MoS 2 inserted in the gap of a gold nanoparticle (AuNP)–alumina (Al 2 O 3 )–gold film (Au Film) structure. Under confocal illumination by a 532 nm CW laser, we observed a 7-fold PL peak intensity enhancement for the cavity-sandwiched MoS 2 at an optimal Al 2 O 3 thickness of 5 nm, corresponding to a local PL enhancement of ∼350 by normalizing the actual illumination area to the cavity’s effective near-field enhancement area. Full-wave simulations reveal a counterintuitive fact that radiation enhancement comes from the non-central area of the cavity rather than the cavity center. By scanning an electric dipole across the nanocavity, we obtained an average radiation enhancement factor of about 65 for an Al 2 O 3 spacer thickness of 4 nm, agreeing well with the experimental thickness and indicating further PL enhancement optimization. Our results indicate the importance of configuration optimization, emitter location and excitation condition when using such plasmonic nanocavities to modulate the radiation properties of quantum emitters.

【 授权许可】

CC BY