A Flip‐Over Plasmonic Structure for Photoluminescence Enhancement of Encapsulated WS2 Monolayers

Minpeng Liang,Jianting Ye,Qihong Chen,Oleksandr Zheliuk,Puhua Wan,Xiaoli Peng,Chunrui Han,Le Zhang

doi:10.1002/adom.202100397

Abstract

AbstractTransition metal dichalcogenide (TMD) monolayers, with their direct band gaps, have attracted wide attention from the fields of photonics and optoelectronics. However, monolayer semiconducting TMDs generally suffer from low excitation absorption and emission efficiency, limiting their further applications. Here a flip‐over plasmonic structure comprised of silver nano‐disk arrays supporting a WS2 monolayer sandwiched by hexagonal boron nitride (h‐BN) layers is demonstrated. The flip‐over configuration optimizes the optical process with a free excitation/emission path from the top and a strong plasmonic interaction from the bottom. As a result, the photoluminescence from the TMD monolayers can be greatly enhanced more than tenfold by optimizing the metasurface, which can be further improved nearly tenfold by optimizing the thickness of bottom h‐BN. This study shows the advantages of using the flip‐over structure, where the plasmonic interaction between the metasurface and TMDs can be tuned by introducing optimized plasmonic arrays and h‐BN layers with suitable thickness. This hybrid device configuration paves a reliable platform to study the light–matter interaction, achieving highly efficient plasmonic TMD devices.

Highlights

Plasmonic metasurfaces made of noble metals can confine and enhance electro magnetic (EM) fields that enables a wide range of applications in optical spectrostions
The WS2 monolayers used in this study were prepared by chemical vapor deposition (CVD)
Both plasmonic array and bottom hexagonal boron nitride (h-BN) play the critical roles on PL enhancement in the hybrid structure composed of silver nano-disk arrays and h-BN encapsulated WS2 monolayers

Summary

Introduction

Plasmonic metasurfaces made of noble metals can confine and enhance electro magnetic (EM) fields that enables a wide range of applications in optical spectrostions. This study shows the advantages of using the flip-over structure, where the plasmonic interaction between the metasurface and TMDs can be tuned by introducing optimized plasmonic arrays and h-BN layers with suitable thickness This hybrid device configuraplasmonic structures, where radiation enhancements were observed in Raman scattering,[8,9,10] light absorption,[11] photo luminescence,[9,10,12,13] and second har monic generation.[14,15]. 2) The thickness of the bottom h-BN of the sandwiched heterostructure, which determines the exci tonic process of TMDs and the interactive strength between plasmonic structures and TMDs. a single layer of h-BN can already isolate the doping effect from the substrate effectively, it requires a much thicker h-BN to smooth out the corrugation caused by the nano-disks that is tens of nanometer in height if the metamaterials are buried below the heterostruc ture in the flip-over configuration

Results and Discussion

Conclusion

Experimental Section

Data Availability Statement