Department of Electrical Engineering, ‡Department of Materials Science and Engineering, and §Precourt Institute for Energy, Stanford University , Stanford, California 94305, United States.
ACS Nano. 2017 Aug 22;11(8):8456-8463. doi: 10.1021/acsnano.7b04100. Epub 2017 Jul 25.
Despite much interest in applications of two-dimensional (2D) fabrics such as MoS, to date most studies have focused on single or few devices. Here we examine the variability of hundreds of transistors from monolayer MoS synthesized by chemical vapor deposition. Ultraclean fabrication yields low surface roughness of ∼3 Å and surprisingly low variability of key device parameters, considering the atomically thin nature of the material. Threshold voltage variation and very low hysteresis suggest variations in charge density and traps as low as ∼10 cm. Three extraction methods (field-effect, Y-function, and effective mobility) independently reveal mobility from 30 to 45 cm/V/s (10th to 90th percentile; highest value ∼48 cm/V/s) across areas >1 cm. Electrical properties are remarkably immune to the presence of bilayer regions, which cause only small conduction band offsets (∼55 meV) measured by scanning Kelvin probe microscopy, an order of magnitude lower than energy variations in Si films of comparable thickness. Data are also used as inputs to Monte Carlo circuit simulations to understand the effects of material variability on circuit variation. These advances address key missing steps required to scale 2D semiconductors into functional systems.
尽管人们对二维 (2D) 织物（如 MoS）的应用很感兴趣，但迄今为止，大多数研究都集中在单个或少数几个器件上。在这里，我们研究了通过化学气相沉积合成的单层 MoS 的数百个晶体管的变异性。超清洁的制造工艺可实现低至约 3 Å 的表面粗糙度，并且考虑到材料的原子薄性质，关键器件参数的变异性也非常低。阈值电压变化和非常低的滞后表明电荷密度和陷阱的变化低至约 10 cm。三种提取方法（场效应、Y 函数和有效迁移率）独立揭示了迁移率在 30 到 45 cm/V/s 之间（10 到 90 百分位；最高值约为 48 cm/V/s），跨越面积大于 1 cm。电特性对存在双层区域具有很强的免疫力，这只会导致扫描开尔文探针显微镜测量的导带偏移较小（约 55 meV），比具有可比厚度的 Si 薄膜的能量变化低一个数量级。数据还被用作蒙特卡罗电路模拟的输入，以了解材料变异性对电路变化的影响。这些进展解决了将二维半导体扩展到功能系统所需的关键缺失步骤。
