Integrated Circuits Based on Bilayer MoS₂ Transistors

Abstract

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 multi-stage 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 two to twelve transistors seamlessly integrated side-byside 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. Keywords: molybdenum disulfide (MoS 2 ), transition metal dichalcogenides (TMD), Two-dimensional (2D)electronics, integrated circuits, ring oscillator.2 Two-dimensional (2D) materials, such as molybdenum disulfide (MoS 2 ) 1 and other members of the transition metal dichalcogenides family, represents the ultimate scaling of material dimension in the vertical direction. Nano-electronic devices built on 2D materials offer many benefits for further miniaturization beyond Moore's Law 2,3 and as a high-mobility option in the emerging field of large-area and low-cost electronics that is currently dominated by low-mobility amorphous silicon 4 and organic semiconductors 5,6 . MoS 2 , a 2D semiconductor material, is also attractive as a potential complement to graphene 7,8,9 for constructing digital circuits on flexible and transparent substrates, while its 1.8 eV bandgap 10,11 is advantageous over silicon for suppressing the source-to-drain tunneling at the scaling limit of transistors 12 . Molybdenum disulfide (MoS 2 ) is a layered semiconductor from the transition metal dichalcogenides material family (TMD), MX 2 (M=Mo, W; X=S, Se, Te) 10,11,19,20 . A single molecular layer of MoS 2 consists of a layer of Mo atoms sandwiched between two layers of sulfur atoms by covalent bonds 10 . The strong intra-layer covalent bonds confer MoS 2 crystals excellent mechanical strength, thermal stability up to 1090 C in inert environment 21 , and a surface free of dangling bonds. On the other hand, the weak inter-layer Van der Waal's force allows single-or fewlayer MoS 2 thin films to be created through micro-mechanical cleavage technique 22 and through anisotropic 2D 3 growth by chemical vapor deposition 23,24 . This unique property of MoS 2 , and 2D ...

Electronics and optoelectronics of two-dimensional transition metal dichalcogenides

“…An integrated circuit composed of two transistors fabricated on a single flake of MoS 2 was operated as a logical inverter, which converts a logical 0 into a logical 1, and as a logical NOR gate 35 , which is one of the universal gates that can be built in combinations to form all other logic operations 120 . Wang et al also recently demonstrated complex integrated circuits built on bilayer MoS 2 , including an inverter, logical NAND gate, static random access memory and five-stage ring oscillator 121 .…”

Spectroscopic Signatures for Interlayer Coupling in MoS2–WSe2 van der Waals Stacking

“…[1][2][3][4][5][6][7][8][9][10][11][12] For example, molybdenum disulphide (MoS2) exhibits an indirect bandgap of 1.2 eV in bulk, but it becomes a direct gap semiconductor (bandgap = 1.8 eV)…”

“…4,8 Hence, monolayer MoS2 transistors have been fabricated and these devices have showed excellent current on/off ratios. [10][11][12] MoS2 is known as an n-type semiconductor due to the presence of S vacancies. Another STMD, tungsten diselenide (WSe2), has just started to attract the attention of numerous scientists due to its p-type characteristics.…”

High-Performance WSe2 Complementary Metal Oxide Semiconductor Technology and Integrated Circuits

“…Two-dimensional (2D) crystals, including graphene, hexagonal boron nitride and transition metal dichalcogenides (TMD), have outstanding properties for developing the next generation of electronic devices [1][2][3][4][5][6][7] . Their extreme thinness, down to a single layer, allows almost perfect electrostatic control of the transistor channel, making them robust to short channel effects and ideal for low power applications 8 .…”