Deterministic and Scalable Generation of Exciton Emitters in 2D Semiconductor Nanodisks

Abstract

valley coupling with the carrier spin, [1][2][3][4] robust exciton and trion emission [5] sensitive to biochemical molecular doping, [6,7] many-body [8,9] and valley [10][11][12][13][14][15][16] physics, and great potential in optoelectronic applications for novel photodetector, [17] electroluminescence light source, [18,19] and lasers. [20] Furthermore, single-photon emitters [21][22][23][24] were found in the transition metal dichalcogenide (TMD) semiconductors, which could serve as a cornerstone for quantum information and communication applications in the visible to near infrared region. [25] Up to date the precise nature of these TMD emitters is still under debate and requires further experimental investigation. Generally, these emitters are attributed to excitons trapped in defectinduced potentials which can be tuned by strain gradient and defect engineering. [26] However, dilute quantum emitters exhibiting narrow photoluminescence (PL) peaks were found in these TMDs and their peak wavelengths were diversely distributed across the broad spectral region. The other candidate for 2D quantum emitter is the twisted TMD heterostructure (i.e., two different TMD monolayers stacked together) with interlayer excitons trapped in periodic Moiré potentials, [27,28] which can be regarded as programmable quantum emitter arrays. [29,30] In recent cryogenic measurements, narrow photoluminescence (PL) peaks due to diverse quantum emitters have been found at random locations of monolayer transition metal dichalcogenides (TMDs), which impedes precise optoelectronic applications. Thus, it is of great importance to truly regulate these localized exciton emissions by deterministic spatial and spectral control. Here, such desired emission is primarily demonstrated in monolayer WS 2 nanodisks. The size-dependent PL studies indicate the clear evolution from the broad defect-band emission to a set of spectrally isolated narrow peaks (linewidth of ≈ sub nm) at 4.2 K, which is associated with the prevailing effect of edge defects with the shrinkage of the disk diameter, providing a narrow emission energy range for bound excitons. When the disk diameter is reduced to 300 nm, more than 80% of emitter peaks are located between 610 and 616 nm, verifying the effective control of emission wavelength of these photon emitters. Furthermore, the strategy is extended to prepare scalable WS 2 nanodisk arrays based on flakes of hundreds of µm, and size-dependent narrow emissions of WSe 2 nanodisks are testified. This work develops a defect-engineering strategy to generate localized exciton emitters toward the promising TMD-based optoelectronic applications.

Exciton–Photon Interactions in Two-Dimensional Semiconductor Microcavities

“…The combinational approach of electron beam lithography and plasma etching to form nanosize structures may be a potential solution. Recently, the emitter-like narrow emission bands in monolayer WS 2 disks prepared by such a strategy have been observed, in which the defect-related localized excitons play a key role . The following step will be the coupling of microcavity-enhanced single-photon emitters with the on-chip waveguides and other functional photonic elements in integrated photonic circuits to verify the technological feasibility, where the waveguides can be made by silicon-based materials or planar photonic crystal membranes .…”

“…Recently, the emitter-like narrow emission bands in monolayer WS 2 disks prepared by such a strategy have been observed, in which the defect-related localized excitons play a key role. 158 The following step will be the coupling of microcavity-enhanced single-photon emitters with the on-chip waveguides and other functional photonic elements in integrated photonic circuits to verify the technological feasibility, where the waveguides can be made by silicon-based materials 159 or planar photonic crystal membranes. 160 Recently, with the silicon-nitride (SiN) microring resonators, the single-photon emission from 2D materials has been efficiently coupled into the SiN waveguide, 159 in which the bandgaps of prevailing 2D semiconductors are suitable to the transmission window of the SiN, i.e., from UV to telecommunication wavelengths.…”

Dynamics of Moiré Exciton in a Twisted MoSe2/WSe2 Heterobilayer

“…[8] The interlayer exciton formed by Coulomb interactions between optically generated electrons and holes in the spatially separated layer is confined within the moiré trap potential and spatially organized as a moiré exciton ensemble. [9][10][11][12] The moiré trapped exciton offers high potential as a platform for many-body physics and the design of quantum optics applications, such as a dense array of coherent quantum emitters; [13,14] however, the discrete excitonic states and dynamics of the confined exciton within the moiré potential remain unexplored.…”