Low Variability in Synthetic Monolayer MoS Devices.

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.