& 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