Quantum Emission in Monolayer WSe2 Transferred onto InP Nanowires

TL;DR

This work addresses the challenge of creating deterministic, on-chip single-photon sources by combining strain-engineered emitters in a two-dimensional TMD with III-V nanowire photonics. It demonstrates that transferring a monolayer WSe2 onto horizontally oriented InP nanowires induces localized strain, producing multiple narrow emission lines in the 715-785 nm range and strong antibunching with $g^{(2)}(0)$ as low as 0.049. AFM-based strain mapping, interpreted via continuum elasticity, reveals highly localized, anisotropic strain around NW facets that correlates with emitter sites. The results establish a viable hybrid platform for integrating TMD quantum emitters with III-V photonics, enabling multiplexed, wavelength-tunable on-chip quantum light sources for scalable quantum photonic networks.

Abstract

Localized quantum emitters in transition-metal dichalcogenides (TMDs) have recently emerged as solid-state candidates for on-demand sources of single photons. Due to the role of strain in the site-selective creation of TMD emitters, their hybrid integration into photonic structures such as cavities and waveguides is possible using pick-and-place methods. Here we investigate quantum emission from a hybrid structure consisting of a monolayer of WSe2 interfaced with horizontally aligned InP nanowires (NWs). Our experiments reveal multiple narrow and bright emission peaks in the 715-785 nm spectral range and g(2)(0) as low as 0.049, indicating strong antibunching and good single photon purity. The faceted nature of III-V NWs provides unique opportunities for strain engineering, including the potential for placement of emitters on the top surface for optimal coupling. Our findings pave the way for realizing hybrid quantum light sources for integrated quantum photonics that could combine III-V quantum dots with TMD emitters into a single platform.

Figures (5)

• Figure 1: (a) Schematic diagram of the optical setup; L: lens, M: mirror, DM: dichroic mirror, BS: beam splitter, LP: long pass filter, TLP: tunable long pass filter, TSP: tunable short pass filter, TT: time tagger, APD: avalanche photo-diode, CCD: charge coupled device. (b) SEM image of an as-grown array of InP NWs at an angle of 45$^\circ$. Inset shows a top view image of a NW with a base diameter of 250 nm. (c) SEM image of InP NWs horizontally deposited onto an Si/SiO$_2$ substrate. (d) Monolayer WSe$_2$/NW hybrid structure. (e) PL spectra of a bare NW, an unstrained monolayer, and a monolayer on NW with excitation powers of 10 $\mu$W, 15 $\mu$W, and 10 $\mu$W, respectively. Scale bars: 10 $\mu$m in (b), 5 $\mu$m in (c), and 3 $\mu$m in (d).
• Figure 2: PL spectra collected from different strained spots (S1 to S6) with excitation powers of 8 $\mu$W (10 $\mu$W for spot S6).
• Figure 3: PL spectra collected at various excitation powers from strained spots S2 [(a)] and S3 [(b)]. The excitation power increases from 1 $\mu$W to 10 $\mu$W in the direction of the arrow, with other power values labeled directly on the respective spectra. PL intensity dependence on excitation power for quantum emissions at (c) 736.47 nm from strained spot S2, (d) 757.70 nm from strained spot S2, and (e) 778.37 nm from strained spot S3. The solid line represents a fit based on the saturation model.
• Figure 4: Second-order autocorrelation measurement: (a) Quantum emission at 778.37 nm from the strained spot S3 with an excitation power of 5 $\mu$W. The inset shows the corresponding emission spectrum at an excitation power of 8 $\mu$W. (b) Quantum emission at 769.69 nm from the strained spot S5 with an excitation power of 5 $\mu$W, with the inset displaying the respective spectrum at 8 $\mu$W. (c-d) Quantum emissions at 726.7 nm and 728.7 nm from the strained spot S6, both measured at an excitation power of 10 µW. The inset shows the corresponding emission spectrum at an excitation power of 10 $\mu$W. Open circles represent raw data, while red solid lines indicate the fitted curves. PL spectra shown in the insets of (a)-(c) are collected using a 1200 g/mm grating.
• Figure 5: Strain mapping of monolayer WSe$_2$ on NWs at location S1, S2, and S3. (a–c) AFM images with height profiles (insets) along the marked line cuts. (d–f) Strain maps computed from AFM data using continuum elastic theory. Line cuts indicate directions for strain extraction. (g–i) Comparison of localized strain profiles along the line cuts from (d-f).