Department of Physics, University of Basel , Klingelbergstrasse 82, CH-4056 Basel, Switzerland.
National Institute for Material Science , 1-1 Namiki, Tsukuba 305-0044, Japan.
Nano Lett. 2018 Feb 14;18(2):1070-1074. doi: 10.1021/acs.nanolett.7b04553. Epub 2018 Jan 31.
The optics of dangling-bond-free van der Waals heterostructures containing transition metal dichalcogenides are dominated by excitons. A crucial property of a confined exciton is the quantum confined Stark effect (QCSE). Here, such a heterostructure is used to probe the QCSE by applying a uniform vertical electric field across a molybdenum disulfide (MoS) monolayer. The photoluminescence emission energies of the neutral and charged excitons shift quadratically with the applied electric field, provided that the electron density remains constant, demonstrating that the exciton can be polarized. Stark shifts corresponding to about half the homogeneous linewidth were achieved. Neutral and charged exciton polarizabilities of (7.8 ± 1.0) × 10 and (6.4 ± 0.9) × 10 D m V at relatively low electron density (∼10 cm) have been extracted, respectively. These values are one order of magnitude lower than the previously reported values but in line with theoretical calculations. The methodology presented here is versatile and can be applied to other semiconducting layered materials.
不含悬挂键的范德华异质结构中过渡金属二卤化物的光学性质主要由激子决定。束缚激子的一个关键特性是量子限制斯塔克效应（QCSE）。在这里，通过在二硫化钼（MoS）单层上施加均匀的垂直电场，使用这种异质结构来探测 QCSE。中性和带电激子的光致发光发射能量与外加电场呈二次方关系，前提是电子密度保持不变，这表明激子可以被极化。实现了约半均匀线宽的斯塔克位移。在相对较低的电子密度（约 10cm）下，分别提取出中性和带电激子的极化率为（7.8±1.0）×10 和（6.4±0.9）×10 D m V。这些值比之前报道的值低一个数量级，但与理论计算相符。本文提出的方法具有通用性，可应用于其他半导体层状材料。
