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Title of the Talk: Single photon emitters in monolayer WS2(Tungsten di-Sulphide) emitting in the visible spectral range

Title of the Talk: Single photon emitters in monolayer WS2(Tungsten di-Sulphide) emitting in the visible spectral range
 
Speaker: Santosh Kumar, Assistant Professor, Department of Physics, IIT Goa. 
 
Date and Time: 5th October, 10 am
 
Venue: Department Conference Room
 
Abstract: 
 
A van der Waals heterostructure/device containing an atomically-thin transition-metal dichalcogenide (TMD) as a single-photon emitting layer is emerging as an intriguing solid-state quantum photonic platform. Various methods of strain engineering have been utilized for creating/inducing the quantum emitters in monolayer (ML) and few-layer TMDs at deterministic locations. Here, we present a simple and cost-effective approach using the spin coating of silica nanoparticles for deterministically creating the spectrally isolated, energetically stable, and narrow-linewidth single-photon emitters in ML-WS2. The emission wavelengths of these quantum emitters are in the visible spectral range where most commercially available single photon detectors work efficiently. We also demonstrate that the low-temperature annealing of this photonic heterostructure, containing ML-WS2, in the vacuum is causing the removal of energetically unstable emitters and leading to the emission of single photons in a narrow wavelength range.
 
Furthermore, we show that the annealing-induced enhanced conformality of the light-emitting layer onto the nanoparticles is causing an enormous tensile strain in the light-emitting layer at the nanoparticle locations. We have estimated a local-strain of up to 1.2% in ML-WS2. The work presented here may provide valuable insights into the quantum properties of 2D materials, which will have implications on the fundamental understanding and technological development of single-photon emitting heterostructures/devices for future quantum photonic technologies.