Scientists have found that the oxygen gap in monolayer tungsten dienide enables it to be used as a single-photonic emitter for quantum optical applications
Scientists have found that the oxygen gap in monolayer tungsten dienide (WSe2) enables it to be used as a single-photonic emitter (SPEs) for quantum optical applications. In recent years, two-dimensional (2 ≤ D) materials with atomic thin cellular lattices have been found in experiments. Spe plays an important role in quantum optics and quantum information processing in the form of a single particle or photons. Spe is developed by using two-dimensional materials such as tungsten dienide, which provides flexibility for potential device and circuit integration in semiconductor manufacturing environment. However, the nature of the spe found in these experiments in tungsten dienide is unclear, which hinders their potential application in quantum applications. Su UK professors and research teams in the Department of Physics at the National University of Singapore have determined that:
The single-photon emission from the local exciton state of tungsten dienide is caused by the oxygen gap existing in the monolayer two-dimensional material. The team combined theoretical calculations with experimental methods to arrive at the results. With the further understanding of single-photonic emission sources, this discovery will help to develop spe, and improve its emission performance using two-dimensional materials. In the study, the team did not find the density functional theory to calculate the intrinsic defects of tungsten dienide materials, and the correlation with the spectra obtained by scanning tunneling spectroscopy, and then focused on the oxygen-related point defects related to tungsten dienide materials. These defects can be easily embedded in the material during synthesis or by environmental passivation.
By eliminating the process, it is found that the defects related to oxygen gap in the lattice are most likely to produce local exciton states at the spectral position observed in the experiment. In this study, the point defects in monolayer tungsten dienide are studied in detail, and the properties and energy of excitons at these defect locations are predicted. Deciphering the origin of single-photonic emitters will help to develop quantum emitters for quantum optical applications using other two-dimensional materials. It is very important to identify point defects in two-dimensional materials for many applications. Recent studies have shown that W vacancy is the most important point defect in two-dimensional tungsten dienide, and theoretical research and prediction. Sulfur vacancy is the most likely inherent point defect in transition metal double halogenated semiconductors.
Using the first principle calculation, scanning tunneling microscope (STM) and scanning transmission electron microscope experiments show that there is no W vacancy in the two-dimensional dienated tungsten grown by cvd. The researchers predict that there are O passivated selenium vacancy (OSe) and O stroma (Oins), in two dimensional tungsten dienide, which may be due to O 2 dissociation in selenium vacancy or the presence of WO3 precursor in CVD growth. These defects make the STM images in good agreement with the experimental results. Because of the experimental observation of single-photonic emission (SPE) of two-dimensional WSE 2, the optical properties of two-dimensional tungsten dienide midpoint defects are very important. The strain gradient makes the exciton distribute funnel in real space. The point defect is a necessary condition for the location of exciton on the length scale, so that photons can emit one at a time. Using the latest gwt-bethe-salpeter equation, it is predicted that only Oins defects will produce local excitons in the energy range of SPE in the previous experiments, which makes them likely to be the source of the previously observed SPE. There are no other point defects (OSe,Se vacancy, W vacancy and SeW inversion) that produce local excitons in the same energy range. A method of realizing SPE in related two-dimensional materials is proposed, and other energy ranges of SPE in two-dimensional tungsten dienide are pointed out for the experimenters.
