Cunningham Paul D, McCreary Kathleen M, Jonker Berend T
U.S. Naval Research Laboratory , Washington, D.C. 20375, United States.
J Phys Chem Lett. 2016 Dec 15;7(24):5242-5246. doi: 10.1021/acs.jpclett.6b02413. Epub 2016 Dec 6.
Reduced dimensionality and strong Coulombic interactions in monolayer semiconductors lead to enhanced many-body interactions. Here, we report Auger recombination, i.e., exciton-exciton annihilation, in large-area chemical vapor deposition-grown monolayer WS. Using ultrafast spectroscopy, we experimentally determine the Auger rate to be 0.089 ± 0.001 cm/s at room temperature, which is an order of magnitude greater than the bulk value. This nonradiative recombination pathway dominates, regardless of excitation energy, for exciton densities greater than 8.0 ± 0.6 × 10 cm and below the Mott density. Higher-energy excitation above the A exciton resonance may initially produce a hot electron-hole gas that precedes exciton formation. Therefore, we use resonant excitation of the A exciton to ensure accuracy and avoid artifacts associated with other photogenerated species.
单层半导体中维度的降低和强库仑相互作用导致多体相互作用增强。在此，我们报道了大面积化学气相沉积生长的单层WS₂中的俄歇复合，即激子 - 激子湮灭。利用超快光谱，我们通过实验确定室温下俄歇速率为0.089±0.001 cm/s，这比体材料值大一个数量级。对于激子密度大于8.0±0.6×10¹² cm⁻²且低于莫特密度的情况，无论激发能量如何，这种非辐射复合途径都占主导地位。高于A激子共振的高能激发最初可能产生在激子形成之前的热电子 - 空穴气。因此，我们使用A激子的共振激发来确保准确性并避免与其他光生物种相关的伪影。
