来源:ACS Publications
Optically addressable spin impurities in crystals along with device engineering provide an attractive route to realizing quantum technologies in the solid state, but reconciling disparate emitter and host material constraints for a given target application is often challenging. Rare-earth ions in two-dimensional (2D) materials could mitigate this problem given the atomic-like transitions of the emitters and the versatile nature of van der Waals systems. Here we combine ion implantation, confocal microscopy, and ab initio calculations to examine the photon emission of Er-doped WS2 flakes. Optical spectroscopy reveals narrow, long-lived photoluminescence lines in the telecom band, which we activate after low-temperature thermal annealing. Spectroscopic and polarization-selective measurements show a uniform response across the ensemble, while the fluorescence brightness remains mostly unchanged with temperature, suggesting nonradiative relaxation channels are inefficient. Our results create opportunities for novel solid state devices coupling 2D-hosted, telecom-band emitters to photonic heterostructures separately optimized for photon manipulation.
We use a custom-made confocal microscope with excitation at 980 nm to examine flake sets exposed to varying Er implantation doses. Figure 1b displays two examples─Flakes 1 and 2, with implantation dose of 1014 ions/cm2─here imaged optically upon reconfiguring the microscope to monitor the back-reflection of the 980 nm excitation beam. As shown in the fluorescence maps, only the first one exhibits telecom-band PL. Our observations indicate the flake thickness─smaller for Flake 2, is the underlying cause. Indeed, a systematic comparison between flakes shows that a thickness of at least 200 nm is necessary to observe Er fluorescence. For the present implantation energy (75 keV), we find a penetration depth of ∼400 nm which, in turn, exposes a large discrepancy with predictions for Er ions extracted from SRIM modeling.