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Atomically thin molybdenum disulfide (MoS2) is an ideal semiconductor material for field-effect transistors (FETs) with sub-10 nm channel lengths. The high effective mass and large bandgap of MoS2 minimize direct source-drain tunneling, while its atomically thin body maximizes the gate modulation efficiency in ultrashort-channel transistors. However, no experimental study to date has approached the sub-10 nm scale due to the multiple challenges related to nanofabrication at this length scale and the high contact resistance traditionally observed in MoS2 transistors. Here, using the semiconducting-to-metallic phase transition of MoS2, we demonstrate sub-10 nm channel-length transistor fabrication by directed self-assembly patterning of mono- and trilayer MoS2. This is done in a 7.5 nm half-pitch periodic chain of transistors where semiconducting (2H) MoS2 channel regions are seamlessly connected to metallic-phase (1T') MoS2 access and contact regions. The resulting 7.5 nm channel-length MoS2 FET has a low off-current of 10 pA/μm, an on/off current ratio of >107, and a subthreshold swing of 120 mV/dec. The experimental results presented in this work, combined with device transport modeling, reveal the remarkable potential of 2D MoS2 for future sub-10 nm technology nodes. [ABSTRACT FROM AUTHOR]

This paper studies band-to-band tunneling in the transverse and lateral directions of van der Waals MoS2/WSe2 heterojunctions. We observe room-temperature negative differential resistance (NDR) in a heterojunction diode comprised of few-layer WSe2 stacked on multilayer MoS2. The presence of NDR is attributed to the lateral band-to-band tunneling at the edge of the MoS2/WSe2 heterojunction. The backward tunneling diode shows an average conductance slope of 75 mV/dec with a high curvature coefficient of 62 V-1. Associated with the tunnel-diode characteristics, a positive-to-negative transconductance in the MoS2/WSe2 heterojunction transistors is observed. The transition is induced by strong interlayer coupling between the films, which results in charge density and energy-band modulation. The sign change in transconductance is particularly useful for multivalued logic (MVL) circuits, and we therefore propose and demonstrate for the first time an MVL-inverter that shows three levels of logic using one pair of p-type transistors. [ABSTRACT FROM AUTHOR]

The article focuses on graphene transistors and photodetectors. It states that the graphene is a thin crystalline film that has unique electronic structure and strong electric field effect. It discusses the properties of single layer graphene based field effect transistor (FET). It also mentions the use and property of bilayer graphene (BLG) and features the operation principles of graphene photodetectors.

Transition metal dichalcogenide (TMD) materials have emerged as promising candidates for thin-film solar cells due to their wide bandgap range across the visible wavelengths, high absorption coefficient, and ease of integration with both arbitrary substrates and conventional semiconductor technologies. However, reported TMD-based solar cells suffer from relatively low external quantum efficiencies (EQE) and low open circuit voltage due to unoptimized design and device fabrication. This paper studies Pt/WSe 2 vertical Schottky junction solar cells with various WSe 2 thicknesses in order to find the optimum absorber thickness. Also, we show that the devices' photovoltaic performance can be improved via Al 2 O 3 passivation, which increases the EQE up to 29.5% at 410 nm wavelength incident light. The overall resulting short circuit current improves through antireflection coating, surface doping, and surface trap passivation effects. Thanks to the Al 2 O 3 coating, this work demonstrates a device with an open circuit voltage ( V OC ) of 380 mV and a short circuit current density ( J SC ) of 10.7 mA/cm 2 . Finally, the impact of Schottky barrier height inhomogeneity at the Pt/WSe 2 contact is investigated as a source of open circuit voltage lowering in these devices.

Obtaining a subthreshold swing (SS) below the thermionic limit of 60 mV dec -1 by exploiting the negative-capacitance (NC) effect in ferroelectric (FE) materials is a novel effective technique to allow the reduction of the supply voltage and power consumption in field effect transistors (FETs). At the same time, two-dimensional layered semiconductors, such as molybdenum disulfide (MoS 2 ), have been shown to be promising candidates to replace silicon MOSFETs in sub-5 nm-channel technology nodes. In this paper, we demonstrate NC MoS 2 FETs by incorporating a ferroelectric Al-doped HfO 2 (Al : HfO 2 ), a technologically compatible material, in the FET gate stack. Al : HfO 2 thin films were deposited on Si wafers by atomic layer deposition. Voltage amplification up to 1.25 times was observed in a FE bilayer stack of Al : HfO 2 /HfO 2 with a Ni metallic intermediate layer. The minimum SS (SS min ) of the NC-MoS 2 FET built on the FE bilayer improved to 57 mV dec -1 at room temperature, compared with SS min = 67 mV dec -1 for the MoS 2 FET with only HfO 2 as a gate dielectric.

Despite rapid progress in 2D molybdenum disulfide (MoS 2 ) research in recent years, MoS 2 field-effect transistors (FETs) still suffer from a high metal-to-MoS 2 contact resistance and low intrinsic mobility, which are major hindrances to their future application. We report an efficient technique to dope thin-film MoS 2 FETs using a poly(vinyl-alcohol) (PVA) polymeric coating. This results in a reduction of the contact resistance by up to 30% as well as a reduction in the channel resistance to 20 kΩ sq -1 . Using a dehydration process, we were able to effectively control the surface interactions between MoS 2 and the more electropositive hydroxyl groups (-OH) of PVA, which provided a controllable and yet reversible increase in the charge carrier density to a value of 8.0 × 10 12 cm -2 . The non-covalent, thus non-destructive, PVA doping of MoS 2 increases the carrier concentration without degrading the mobility, which shows a monotonic increase while enhancing the doping effect. The PVA doping technique is then exploited to create heavily doped access regions to the intrinsic MoS 2 channel, which yields 200% increase of the ON-state source-drain current. This establishes PVA doping as an effective approach to enhance the transport properties of MoS 2 FETs for a variety of applications.

Atomically thin molybdenum disulfide (MoS 2 ) is an ideal semiconductor material for field-effect transistors (FETs) with sub-10 nm channel lengths. The high effective mass and large bandgap of MoS 2 minimize direct source-drain tunneling, while its atomically thin body maximizes the gate modulation efficiency in ultrashort-channel transistors. However, no experimental study to date has approached the sub-10 nm scale due to the multiple challenges related to nanofabrication at this length scale and the high contact resistance traditionally observed in MoS 2 transistors. Here, using the semiconducting-to-metallic phase transition of MoS 2 , we demonstrate sub-10 nm channel-length transistor fabrication by directed self-assembly patterning of mono- and trilayer MoS 2 . This is done in a 7.5 nm half-pitch periodic chain of transistors where semiconducting (2H) MoS 2 channel regions are seamlessly connected to metallic-phase (1T') MoS 2 access and contact regions. The resulting 7.5 nm channel-length MoS 2 FET has a low off-current of 10 pA/μm, an on/off current ratio of >10 7 , and a subthreshold swing of 120 mV/dec. The experimental results presented in this work, combined with device transport modeling, reveal the remarkable potential of 2D MoS 2 for future sub-10 nm technology nodes.