Linearly\nPolarized Luminescence of Atomically Thin\nMoS₂ Semiconductor Nanocrystals

Abstract

Atomically thin layers\nof transition-metal dichalcogenides semiconductors,\nsuch as MoS₂, exhibit strong and circularly polarized light\nemission due to inherent crystal symmetries, pronounced spin–orbit\ncoupling, and out-of-plane dielectric and spatial confinement. While\nthe layer-by-layer confinement is well-understood, the understanding\nof the impact of in-plane quantization in their optical spectrum is\nfar behind. Here, we report the optical properties of atomically thin\nMoS₂ colloidal semiconductor nanocrystals. In addition\nto the spatial-confinement effect leading to their blue wavelength\nemission, the high quality of our MoS₂ nanocrystals is\nrevealed by narrow photoluminescence, which allows us to resolve multiple\noptically active transitions, originating from quantum-confined excitons\n(coupled electron–hole pairs). Surprisingly, in stark contrast\nto monolayer MoS₂, the luminescence of the lowest-energy\nlevels is linearly polarized and persists up to <i>room temperature</i>, meaning that it could be exploited in a variety of light-emitting\napplications.