Department of Materials Science and Engineering, ‡Department of Physics, ∥Analytical Instrumentation Facility, and ⊥Department of Electrical and Computer Engineering, North Carolina State University , Raleigh, North Carolina 27695, United States.
Nano Lett. 2015 Jan 14;15(1):486-91. doi: 10.1021/nl5038177. Epub 2014 Dec 16.
Semiconductor heterostructures provide a powerful platform to engineer the dynamics of excitons for fundamental and applied interests. However, the functionality of conventional semiconductor heterostructures is often limited by inefficient charge transfer across interfaces due to the interfacial imperfection caused by lattice mismatch. Here we demonstrate that MoS(2)/WS(2) heterostructures consisting of monolayer MoS(2) and WS(2) stacked in the vertical direction can enable equally efficient interlayer exciton relaxation regardless the epitaxy and orientation of the stacking. This is manifested by a similar 2 orders of magnitude decrease of photoluminescence intensity in both epitaxial and nonepitaxial MoS(2)/WS(2) heterostructures. Both heterostructures also show similarly improved absorption beyond the simple superimposition of the absorptions of monolayer MoS(2) and WS(2). Our result indicates that 2D heterostructures bear significant implications for the development of photonic devices, in particular those requesting efficient exciton separation and strong light absorption, such as solar cells, photodetectors, modulators, and photocatalysts. It also suggests that the simple stacking of dissimilar 2D materials with random orientations is a viable strategy to fabricate complex functional 2D heterostructures, which would show similar optical functionality as the counterpart with perfect epitaxy.
半导体异质结构为工程学激子动力学提供了一个强大的平台，无论是出于基础研究还是实际应用的目的。然而，由于晶格失配导致的界面不完美，传统半导体异质结构的电荷转移效率往往较低，从而限制了其功能。在这里，我们证明了由垂直堆叠的单层 MoS2 和 WS2 组成的 MoS2/WS2 异质结构可以实现高效的层间激子弛豫，而与堆叠的外延和取向无关。这表现在外延和非外延 MoS2/WS2 异质结构中，光致发光强度都以相似的 2 个数量级降低。这两种异质结构都表现出相似的吸收增强，超出了单层 MoS2 和 WS2 吸收的简单叠加。我们的结果表明，二维异质结构对于光子器件的发展具有重要意义，特别是对于那些要求高效激子分离和强吸收的器件，如太阳能电池、光电探测器、调制器和光催化剂。这也表明，具有随机取向的不同二维材料的简单堆叠是制造复杂功能二维异质结构的可行策略，其光学功能与具有完美外延的异质结构相似。
