Integrated circuits based on bilayer MoS ₂ transistors

Two-dimensional (2D) materials, such as molybdenum disulfide (MoS ₂), have been shown to exhibit excellent electrical and optical properties. The semiconducting nature of MoS ₂ allows it to overcome the shortcomings of zero-bandgap graphene, while still sharing many of graphene's advantages for electronic and optoelectronic applications. Discrete electronic and optoelectronic components, such as field-effect transistors, sensors, and photodetectors made from few-layer MoS ₂ show promising performance as potential substitute of Si in conventional electronics and of organic and amorphous Si semiconductors in ubiquitous systems and display applications. An important next step is the fabrication of fully integrated multistage circuits and logic building blocks on MoS ₂ to demonstrate its capability for complex digital logic and high-frequency ac applications. This paper demonstrates an inverter, a NAND gate, a static random access memory, and a five-stage ring oscillator based on a direct-coupled transistor logic technology. The circuits comprise between 2 to 12 transistors seamlessly integrated side-by-side on a single sheet of bilayer MoS ₂. Both enhancement-mode and depletion-mode transistors were fabricated thanks to the use of gate metals with different work functions.