Strong exciton-photon coupling in large area MoSe2 and WSe2 heterostructures fabricated from two-dimensional materials grown by chemical vapor deposition

Daniel J Gillard,Aurélien A P Trichet,Kyung Yeol Ma,Thomas P Lyons,Kyriacos Georgiou,Toby Severs Millard,Seongjoon Ahn,A-Rang Jang,Hyeon Suk Shin,Jason M Smith,David G Lidzey,Armando Genco,Alexander I Tartakovskii,Rahul Jayaprakash

doi:10.1088/2053-1583/abc5a1

Abstract

Two-dimensional semiconducting transition metal dichalcogenides embedded in optical microcavities in the strong exciton-photon coupling regime may lead to promising applications in spin and valley addressable polaritonic logic gates and circuits. One significant obstacle for their realization is the inherent lack of scalability associated with the mechanical exfoliation commonly used for fabrication of two-dimensional materials and their heterostructures. Chemical vapor deposition offers an alternative scalable fabrication method for both monolayer semiconductors and other two-dimensional materials, such as hexagonal boron nitride. Observation of the strong light-matter coupling in chemical vapor grown transition metal dichalcogenides has been demonstrated so far in a handful of experiments with monolayer molybdenum disulfide and tungsten disulfide. Here we instead demonstrate the strong exciton-photon coupling in microcavities composed of large area transition metal dichalcogenide/hexagonal boron nitride heterostructures made from chemical vapor deposition grown molybdenum diselenide and tungsten diselenide encapsulated on one or both sides in continuous few-layer boron nitride films also grown by chemical vapor deposition. These transition metal dichalcogenide/hexagonal boron nitride heterostructures show high optical quality comparable with mechanically exfoliated samples, allowing operation in the strong coupling regime in a wide range of temperatures down to 4 Kelvin in tunable and monolithic microcavities, and demonstrating the possibility to successfully develop large area transition metal dichalcogenide based polariton devices.

Highlights

Monolayers of transition metal dichalcogenides (TMDs) are promising semiconductors with unique electrical and optical properties arising from the quantum confinement experienced by the electrons and holes in the two-dimensional (2D) structure[1,2]
The results presented in this work demonstrate the possibility to fabricate large area polariton devices exploiting high quality TMD based heterostructures made from Chemical vapor deposition (CVD)-grown materials, paving the way for future scalable TMD-polaritonic circuits
HS2 (Fig.1(b)), WSe2 monolayers are grown by CVD directly on few-layer hexagonal boron nitride (hBN), grown by CVD

Summary

Introduction

Monolayers of transition metal dichalcogenides (TMDs) are promising semiconductors with unique electrical and optical properties arising from the quantum confinement experienced by the electrons and holes in the two-dimensional (2D) structure[1,2]. The breaking of spatial inversion symmetry in the 2D lattice and a large spin-orbit coupling generate spin-valley locked optically addressable excitons at the K and K points of the momentum space[3,5]. These exceptional properties can be further enriched by integrating the TMDs within optical resonators enabling the strong exciton-photon coupling regime, where confined photons and excitons hybridize into new states called polaritons[6–12]. Polaritons in TMDs. 3 acquire novel properties arising from the valley pseudo-spin degree of freedom of excitons[13,14], and further provide enhanced valley coherence for excitons strongly coupled with long-lived cavity photons[15,16]. United to the valley degree of freedom of TMD monolayers, these phenomena could be exploited to create large scale all-optical polariton circuits and quantum networks[25,26]

Methods

Results

Conclusion