Department of Physics and ‡Department of Mechanical Engineering, University of Texas at Austin , Austin, Texas 78712, United States.
Nano Lett. 2014 Aug 13;14(8):4682-6. doi: 10.1021/nl501782e. Epub 2014 Jul 16.
The success of isolating small flakes of atomically thin layers through mechanical exfoliation has triggered enormous research interest in graphene and other two-dimensional materials. For device applications, however, controlled large-area synthesis of highly crystalline monolayers with a low density of electronically active defects is imperative. Here, we demonstrate the electrical imaging of dendritic ad-layers and grain boundaries in monolayer molybdenum disulfide (MoS2) grown by a vapor transport technique using microwave impedance microscopy. The micrometer-sized precipitates in our films, which appear as a second layer of MoS2 in conventional height and optical measurements, show ∼ 2 orders of magnitude higher conductivity than that of the single layer. The zigzag grain boundaries, on the other hand, are shown to be more resistive than the crystalline grains, consistent with previous studies. Our ability to map the local electrical properties in a rapid and nondestructive manner is highly desirable for optimizing the growth process of large-scale MoS2 atomic layers.
通过机械剥落成功分离出原子级薄的小片，引发了人们对石墨烯和其他二维材料的极大研究兴趣。然而，对于器件应用，具有低电子活性缺陷密度的高结晶单层的可控大面积合成是必不可少的。在这里，我们使用微波阻抗显微镜展示了通过气相输运技术生长的单层二硫化钼 (MoS2) 中枝晶亚层和晶界的电成像。在我们的薄膜中，微米级的沉淀物在常规高度和光学测量中表现为第二层 MoS2，其电导率比单层高出约 2 个数量级。另一方面，锯齿形晶界比结晶晶粒的电阻更大，这与之前的研究一致。我们能够以快速和非破坏性的方式绘制局部电特性的能力，非常有利于优化大规模 MoS2 原子层的生长过程。
