& These authors contributed equally to this work 2 ABSTRACT.The appearance of single photon sources in atomically thin semiconductors holds great promises for the development of a flexible and ultra-compact quantum technology, in which elastic strain engineering can be used to tailor their emission properties. Here, we show a compact and hybrid 2D-semiconductorpiezoelectric device that allows for controlling the energy of single photons emitted by quantum emitters localized in wrinkled WSe2 monolayers. We demonstrate that strain fields exerted by the piezoelectric device can be used to tune the energy of localized excitons in WSe2 up to 18 meV in a reversible manner, while leaving the single photon purity unaffected over a wide range. Interestingly, we find that the magnitude and in particular the sign of the energy shift as a function of stress is emitter dependent. With the help of finite element simulations we suggest a simple model that explains our experimental observations and, furthermore, discloses that the type of strain (tensile or compressive) experienced by the quantum emitters strongly depends on their localization across the wrinkles. Our findings are of strong relevance for the practical implementation of single photon devices based on two-dimensional materials as well as for understanding the effects of strain on their emission properties. KEYWORDS: single photon emitters, 2D materials, elastic strain engineering, photoluminescence, tungsten diselenide monolayers, piezoelectric devices MAIN TEXTThe family of two-dimensional (2D) semiconductor transition metal dichalcogenides (TMDs), including WS2, WSe2, MoS2 or MoSe2, offers several advantages for optoelectronic and photonic applications. They possess a variety of properties such as direct bandgap when thinned down to the monolayer, quantum confinement due to their reduced out-of-plane dimensionality, large oscillator strength and quantum efficiency, optically controlled injection of electrons with defined spins for quantum spintronics and spinphoton interfacing 1,2 . Moreover, functional multilayer heterostructures can be easily built up by simply

We demonstrate a deterministic Purcell-enhanced single-photon source realized by integrating an atomically thin WSe2 layer with a circular Bragg grating cavity. The cavity significantly enhances the photoluminescence from the atomically thin layer, and supports single-photon generation with g (2) (0)<0.25. We observe a consistent increase of the spontaneous emission rate for WSe2 emitters located in the center of the Bragg grating cavity. These WSe2 emitters are self-aligned and deterministically coupled to such a broadband cavity, configuring a new generation of deterministic single-photon sources, characterized by their simple and low-cost production and intrinsic scalability.

We demonstrate a Purcell-enhanced single-photon source realized by the fabrication of a hybrid III–V/dielectric circular Bragg grating cavity directly bonded onto a piezoelectric actuator. Such a kind of photonic system offers the potential for broadband high photon extraction efficiency and spontaneous emission rate enhancement. This device allows for reversible spectral tuning of the embedded quantum dot emitters and pure triggered single-photon generation with g (2)(0) = (1.5 ± 0.05) × 10–3. By applying 18 kV/cm electric filled to the piezosubstrate, we achieve a tuning range larger than 0.78 meV for quantum dots in resonance with the cavity mode. Spontaneous emission lifetimes smaller than 200 ps, in conjunction with a systematic increase of the spontaneous emission rate on resonance with the broadband cavity mode, verify that our device operates deep in the Purcell regime. Our strain-tunable, broadband Purcell-enhanced device represents a crucial building block for scalable quantum technologies.

Scalable quantum photonic architectures demand highly efficient, high-purity single-photon sources, which can be frequency matched via external tuning. We demonstrate a singlephoton source based on an InAs quantum dot embedded in a micropillar resonator, which is frequency tunable via externally-applied stress. Our platform combines the advantages of a Bragg micropillar cavity and the piezo-strain-tuning technique enabling single photon spontaneous emission enhancement via the Purcell effect and quantum dot (QD) with tunable wavelength. Our optomechanical platform has been implemented by integration of semiconductor-based QD-micropillars on a piezoelectric substrate. The fabricated device exhibits spontaneous emission enhancement with a Purcell factor of 4.4±0.7 and allows for a pure triggered single-photon generation with g (2) (0) < 0.07 under resonant excitation. A quantum dot emission energy tuning range of 0.75 meV for 27 kV/cm applied to the piezo substrate has been achieved. Our results pave the way towards the scalable implementation of single-photon quantum photonic technologies using optoelectronic devices.

This paper presents the results of experimental investigations of the plasma surface modification of a poly(methyl methacrylate) (PMMA) polymer and PMMA composites with a [6,6]-phenyl-C61-butyric acid methyl ester fullerene derivative (PC61BM). An atmospheric pressure microwave (2.45 GHz) argon plasma sheet was used. The experimental parameters were: an argon (Ar) flow rate (up to 20 NL/min), microwave power (up to 530 W), number of plasma scans (up to 3) and, the kind of treated material. In order to assess the plasma effect, the possible changes in the wettability, roughness, chemical composition, and mechanical properties of the plasma-treated samples’ surfaces were evaluated by water contact angle goniometry (WCA), atomic force microscopy (AFM), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). The best result concerning the water contact angle reduction was from 83° to 29.7° for the PMMA material. The ageing studies of the PMMA plasma-modified surface showed long term (100 h) improved wettability. As a result of plasma treating, changes in the samples surface roughness parameters were observed, however their dependence on the number of plasma scans is irregular. The ATR-FTIR spectra of the PMMA plasma-treated surfaces showed only slight changes in comparison with the spectra of an untreated sample. The more significant differences were demonstrated by XPS measurements indicating the surface chemical composition changes after plasma treatment and revealing the oxygen to carbon ratio increase from 0.1 to 0.4.