2023 User Research Highlights
High-density, localized quantum emitters in strained 2D semiconductors

Project Summary: Two-dimensional semiconductors have recently emerged as a host material for quantum emitters of single photons. While several reports on defect- and strain-induced single photon emission from 2D chalcogenides exist, a bottom-up, lithography-free approach to producing a high density of emitters has remained elusive. Here, we demonstrate a bottom-up, scalable, and

lithography-free approach for creating large areas of localized emitters with high density (∼150 emitters/mm2) in a WSe2 monolayer. We induce strain inside the WSe2 monolayer with high spatial density by conformally placing the WSe2 monolayer over a uniform array of 10 nm Pt nanoparticles. Cryogenic, time-resolved, and gate-tunable luminescence measurements combined with near-field luminescence spectroscopy suggest the formation of localized states in strained regions that emit single photons with a high spatial density. Our approach of using a metal nanoparticle array to generate a high density of strained quantum emitters will be applied to scalable, tunable, and versatile quantum light sources.

Published in: ACS Nano 16, 9651-9659 (2022).

2DCC Role: The research used wafer-scale WSe2 monolayers synthesized by MOCVD at the 2DCC facility.

What Has Been Achieved: Demonstration of localized quantum emitters in WSe2 formed by draping the monolayer over a uniform array of 10 nm Pt nanoparticles. The strain in the WSe2 at the apex of the nanoparticle induces defects which act as single photon emitters.

Importance of the Achievement: Prior work demonstrated strained quantum emitters using nanopillars in silicon formed by lithography and etching. The technique reported in this paper, which uses self-assembled nanoparticles, provides a scalable and lithography-free approach to form single photon emitters which can be integrated on a variety of platforms.

Unique Feature(s) of the MIP that Enabled this Achievement:  The fabrication of the samples was enabled by the availability of high optical quality wafer-scale WSe2 monolayers synthesized in the 2DCC facility. 

(If Applicable) Publication:

G. Kim, et al., “High-density, localized quantum emitters in strained 2D semiconductors,” ACS Nano 16, 9651-9659 (2022)  https://doi.org/10.1021/acsnano.2c02974

Acknowledgements: D.J. and G.K. acknowledge primary support for this work by the Air Force Office of Scientific Research (AFOSR) FA2386-20-1-4074 and partial support from FA2386-21-1-4063. D.J., E.A.S., and P.K. acknowledge partial support from National Science Foundation (DMR-1905853) and support from University of Pennsylvania Materials Research Science and Engineering Center (MRSEC) (DMR-1720530) in addition to usage of MRSEC-supported facilities. The sample fabrication, assembly, and characterization were carried out at the Singh Center for Nanotechnology at the University of Pennsylvania, which is supported by the National Science Foundation (NSF) National Nanotechnology Coordinated Infrastructure Program grant NNCI-1542153. K.J. was supported by a Vagelos Institute of Energy Science and Technology graduate fellowship. The large area-MOCVD-WSe2 monolayer samples were provided by the 2D Crystal ConsortiumMaterials Innovation Platform (2DCC-MIP) facility at The Pennsylvania State University, which is funded by NSF under cooperative agreement DMR-1539916. J.R.H. acknowledges support from the Air Force Office of Scientific Research (Program Manager Dr. Gernot Pomrenke) under award number FA9550-20RYCOR059. M.R. acknowledges support from Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) for a Walter Benjamin Fellowship (award no. RA 3646/1-1). J.S. acknowledges support by the National Research Foundation of Korea (MSIT) (grant nos. NRF-2020R1C1C1011219 and NRF-2020M3H3A1100938). D.J. and H.-M.K. acknowledge partial support from the Center of Undergraduate Research Fellowships and Class of 1971 Robert J. Holtz Fund Research Grant. N.R.G. acknowledges the support from the Air Force Office of Scientific Research grant FA9550-19RYCOR050.