(Energy.gov) Scientists discovered a new method for developing sources that emit light as single photons (quantum emitters) by exploiting strain in a two-dimensional material. The research at Los Alamos National Laboratory was funded by the Laboratory Directed Research and Development Program and the Center for Integrated Nanotechnologies (CINT), a DOE nanoscience research center and scientific user facility jointly operated by Los Alamos and Sandia national laboratories.
This method creates spatially localized and well-separated emission sites in a continuous tungsten/selenium thin-film. The film is created by a multi-step diffusion-mediated gas source chemical vapor deposition technique, then transferred onto an array of ultra-sharp silicon dioxide tips. Because the film is very thin, it conforms to the radius of the tips and bends towards the substrate by more than a few percent. The resulting strain is enough to change the electronic structure, but only at the tips. The affected area emits light of a different color and nature than light from the rest of the film. The team observed bound exciton lifetimes that were one order of magnitude longer compared to emissions that were intrinsic to the film. Single photon generation at the tip apex was confirmed by a laser technique called Hanbury-Brown-Twiss quantum interferometry. Future studies looking at the role of mechanical deformation in creating these quantum emission sites may enable a route to control quantum optical properties with strain. While engineering of quantum emission in two-dimensional materials is still at an early stage, this research provides a path toward scale-up to larger quantum material systems.