The compelling demand for higher performance and lower power consumption in electronic systems is the main driving force of the electronics industry's quest for devices and/or architectures based on new materials. Here, we provide a review of electronic devices based on two-dimensional materials, outlining their potential as a technological option beyond scaled complementary metal-oxide-semiconductor switches. We focus on the performance limits and advantages of these materials and associated technologies, when exploited for both digital and analog applications, focusing on the main figures of merit needed to meet industry requirements. We also discuss the use of two-dimensional materials as an enabling factor for flexible electronics and provide our perspectives on future developments.

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 ...

Hexagonal boron nitride (h-BN) is very attractive for many applications, particularly, as protective coating, dielectric layer/substrate, transparent membrane, or deep ultraviolet emitter. In this work, we carried out a detailed investigation of h-BN synthesis on Cu substrate using chemical vapor deposition (CVD) with two heating zones under low pressure (LP). Previous atmospheric pressure (AP) CVD syntheses were only able to obtain few layer h-BN without a good control on the number of layers. In contrast, under LPCVD growth, monolayer h-BN was synthesized and time-dependent growth was investigated. It was also observed that the morphology of the Cu surface affects the location and density of the h-BN nucleation. Ammonia borane is used as a BN precursor, which is easily accessible and more stable under ambient conditions than borazine. The h-BN films are characterized by atomic force microscopy, transmission electron microscopy, and electron energy loss spectroscopy analyses. Our results suggest that the growth here occurs via surface-mediated growth, which is similar to graphene growth on Cu under low pressure. These atomically thin layers are particularly attractive for use as atomic membranes or dielectric layers/substrates for graphene devices.

We engineered functional cardiac patches by seeding neonatal rat cardiomyocytes onto carbon nanotube (CNT) incorporated photocrosslinkable gelatin methacrylate (GelMA) hydrogel. The resulting cardiac constructs showed excellent mechanical integrity and advanced electrophysiological functions. Specifically, myocardial tissues cultured on 50 μm thick CNT-GelMA showed 3 times higher spontaneous synchronous beating rates and 85% lower excitation threshold, compared to those cultured on pristine GelMA hydrogels. Our results indicate that the electrically conductive and nanofibrous networks formed by CNTs within a porous gelatin framework is the key characteristics of CNT-GelMA leading to improved cardiac cell adhesion, organization, and cell-cell coupling. Centimeter-scale patches were released from glass substrates to form 3D biohybrid actuators, which showed controllable linear cyclic contraction/extension, pumping, and swimming actuations. In addition, we demonstrate for the first time that cardiac tissues cultured on CNT-GelMA resist damage by a model cardiac inhibitor as well as a cytotoxic compound. Therefore, incorporation of CNTs into gelatin, and potentially other biomaterials, could be useful in creating multifunctional cardiac scaffolds for both therapeutic purposes and in vitro studies. These hybrid materials could also be used for neuron and other muscle cells to create tissue constructs with improved organization, electroactivity, and mechanical integrity.

Advanced beyond-silicon electronic technology requires discoveries of both new channel materials and ultralow-resistance contacts 1,2 . Atomically thin two-dimensional (2D) semiconductors have great potential for realizing high-performance electronic devices 1,3 . However, because of metal-induced gap states (MIGS) 4-7 , energy barriers at the metalsemiconductor interface, which fundamentally lead to high contact resistances and poor current-delivery capabilities, have restrained the advancement of 2D semiconductor transistors to date 2,8,9 . Here, we report a novel ohmic contact technology between semimetallic bismuth and semiconducting monolayer transition metal dichalcogenides (TMDs) where MIGS is sufficiently suppressed and degenerate states in the TMD are spontaneously formed in contact with bismuth. Through this approach, we achieve zero Schottky barrier height, a record-low contact resistance (R C ) of 123 Ω μm, and a recordhigh on-state current density (I ON ) of 1135 µA µm -1 on monolayer MoS 2 . We also demonstrate that excellent ohmic contacts can be formed on various monolayer semiconductors, including MoS 2 , WS 2 , and WSe 2 . Our reported R C values are a significant improvement for 2D semiconductors, and approaching the quantum limit. This technology unveils the full potential of high-performance monolayer transistors that are on par with the state-of-the-art 3D semiconductors, enabling further device down-scaling and extending Moore's Law.The electrical contact resistance at a metal-semiconductor (M-S) interface has been an increasingly critical, yet unsolved issue for the semiconductor industry, hindering the ultimate