Peimyoo Namphung, Wu Hsin-Yu, Escolar Janire, De Sanctis Adolfo, Prando Gabi, Vollmer Frank, Withers Freddie, Riis-Jensen Anders Christian, Craciun Monica Felicia, Thygesen Kristian Sommer, Russo Saverio
Centre for Graphene Science, College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter EX4 4QL, U.K.
Living Systems Institute, Department of Physics and Astronomy, University of Exeter, Exeter EX4 4QD, U.K.
ACS Appl Mater Interfaces. 2020 Dec 9;12(49):55134-55140. doi: 10.1021/acsami.0c14696. Epub 2020 Nov 24.
Tailoring of the band gap in semiconductors is essential for the development of novel devices. In standard semiconductors, this modulation is generally achieved through highly energetic ion implantation. In two-dimensional (2D) materials, the photophysical properties are strongly sensitive to the surrounding dielectric environment presenting novel opportunities through van der Waals heterostructures encompassing atomically thin high-κ dielectrics. Here, we demonstrate a giant tuning of the exciton binding energy of the monolayer WSe as a function of the dielectric environment. Upon increasing the average dielectric constant from 2.4 to 15, the exciton binding energy is reduced by as much as 300 meV in ambient conditions. The experimentally determined exciton binding energies are in excellent agreement with the theoretical values predicted from a Mott-Wannier exciton model with parameters derived from first-principles calculations. Finally, we show how texturing of the dielectric environment can be used to realize potential-well arrays for excitons in 2D materials, which is a first step toward exciton metamaterials.
半导体带隙的定制对于新型器件的开发至关重要。在标准半导体中，这种调制通常通过高能离子注入来实现。在二维（2D）材料中，光物理性质对周围介电环境高度敏感，通过包含原子级薄高κ电介质的范德华异质结构提供了新的机会。在此，我们展示了单层WSe的激子结合能随介电环境的巨大调谐。在环境条件下，将平均介电常数从2.4提高到15时，激子结合能降低了多达300 meV。实验测定的激子结合能与从具有第一性原理计算得出的参数的莫特-万尼尔激子模型预测的理论值非常吻合。最后，我们展示了如何利用介电环境的纹理化来实现二维材料中激子的势阱阵列，这是迈向激子超材料的第一步。
