  Next-generation electronics calls for new materials beyond silicon for
increased functionality, performance, and scaling in integrated circuits.
Carbon nanotubes and semiconductor nanowires are at the forefront of these
materials, but have challenges due to the complex fabrication techniques
required for large-scale applications. Two-dimensional (2D) gapless graphene
and semiconducting transition metal dichalcogenides (TMDCs) have emerged as
promising electronic materials due to their atomic thickness, chemical
stability and scalability. Difficulties in the assembly of 2D electronic
structures arise in the precise spatial control over the metallic and
semiconducting atomic thin films. Ultimately, this impedes the maturity of
integrating atomic elements in modern electronics. Here, we report the
large-scale spatially controlled synthesis of the single-layer semiconductor
molybdenum disulfide (MoS2) laterally in contact with conductive graphene.
Transition electron microscope (TEM) studies reveal that the single-layer MoS2
nucleates at the edge of the graphene, creating a lateral 2D heterostructure.
We demonstrate such chemically assembled 2D atomic transistors exhibit high
transconductance (10 uS), on-off ratios (10^6), and mobility (20 cm^2 V^-1
s^-1). We assemble 2D logic circuits, such as a heterostructure NMOS inverter
with a high voltage gain, up to 70, enabled by the precise site selectivity
from atomically thin conducting and semiconducting crystals. This scalable
chemical assembly of 2D heterostructures may usher in a new era in
two-dimensional electronic circuitry and computing.
