Murthy Akshay A, Stanev Teodor K, Dos Reis Roberto, Hao Shiqiang, Wolverton Christopher, Stern Nathaniel P, Dravid Vinayak P
ACS Nano. 2020 Feb 25;14(2):1569-1576. doi: 10.1021/acsnano.9b06581. Epub 2020 Feb 11.
Layered transition metal dichalcogenides offer many attractive features for next-generation low-dimensional device geometries. Due to the practical and fabrication challenges related to methods, the atomistic dynamics that give rise to realizable macroscopic device properties are often unclear. In this study, transmission electron microscopy techniques are utilized in order to understand the structural dynamics at play, especially at interfaces and defects, in the prototypical film of monolayer MoS under electrical bias. Through our sample fabrication process, we clearly identify the presence of mass transport in the presence of a lateral electric field. In particular, we observe that the voids present at grain boundaries combine to induce structural deformation. The electric field mediates a net vacancy flux from the grain boundary interior to the exposed surface edge sites that leaves molybdenum clusters in its wake. Following the initial biasing cycles, however, the mass flow is largely diminished and the resultant structure remains stable over repeated biasing. We believe insights from this work can help explain observations of nonuniform heating and preferential oxidation at grain boundary sites in these materials.
层状过渡金属二硫属化物为下一代低维器件几何结构提供了许多吸引人的特性。由于与方法相关的实际和制造挑战，导致可实现的宏观器件性能的原子动力学往往不明确。在本研究中，利用透射电子显微镜技术来了解在电偏压下单层MoS典型薄膜中起作用的结构动力学，特别是在界面和缺陷处的结构动力学。通过我们的样品制备过程，我们清楚地确定了在横向电场存在下质量传输的存在。特别是，我们观察到晶界处存在的空隙结合起来会引起结构变形。电场介导了从晶界内部到暴露表面边缘位点的净空位通量，在其尾迹中留下钼簇。然而，在初始偏压循环之后，质量流大大减少，并且在重复偏压下所得结构保持稳定。我们相信这项工作的见解有助于解释这些材料中晶界处不均匀加热和优先氧化的观察结果。
