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While transition‐metal thiophosphate (MPX3) materials have been a subject of extensive research in recent years, experimental studies on MPX3‐based memristors are still in their early stages, with device performance being less than ideal. Here, the successful fabrication of high‐yield, high‐performance, and uniform memristors are demonstrated to possess desired characteristics for neuromorphic computing using a single‐crystalline few‐layered manganese phosphorus trisulfide (MnPS3) as a resistive switching medium. The Ti/MnPS3/Au memristor exhibits small switching voltage (<1 V), long memory retention (104 s), fast switching speed (≈20 ns), high On/Off ratio (nearly two orders of magnitude), and simultaneously achieves emulation of synaptic weight plasticity. The microscopic investigation of the structural and chemical characteristics of the few‐layer MnPS3 reveals the presence of structural defects and residual Ti throughout the stacked layer following the application of voltage, which contributes to the uniformity of switching with a low set voltage. With highly linear and symmetric analog weight updates coupled with the capability of accurate decimal arithmetic operations, a high accuracy of 95.15% in supervised learning using the MNIST handwritten recognition dataset is achieved in the artificial neural network. Furthermore, convolutional image processing can be implemented using hardware multiply‐and‐accumulate operation in an experimental memristor crossbar array. [ABSTRACT FROM AUTHOR]

A surface potential based compact model for two-dimensional field effect transistors (2D-FETs) is proposed to incorporate the structural disorders induced transition behaviors among variable range hopping (VRH), nearest neighbor hopping (NNH), and band-like transport in most 2D materials. These functions coupled with effective transport energy and multiple trapping and releasing theory enable our developed model to predict the temperature and carrier density dependent current characteristics. Its validity is confirmed by the experimental results such as the metal insulator transition (MIT) in transition metal dichalcogenides and VRH-NNH transition in black phosphorus nanoribbon. Based on this model, the band-tail effects on the crossover gate voltage of MIT behavior are quantitatively investigated. It is found that the transition behavior is closely related to the distribution of the band-tail states. Furthermore, this model is implemented in Verilog-A for circuit-level prediction and evaluation of 2D-FETs to provide deeper insight into the relationship between material properties, device physics, and circuit performances. [ABSTRACT FROM AUTHOR]

Unceasing efforts have been devoted to photonics based on black phosphorus ever since it came under the spotlight of two-dimensional materials research six years ago. The direct bandgap of black phosphorus is tunable by layer number, vertical electric field, and chemical doping, covering a broad spectrum for efficient light manipulation. The optical anisotropy further enables the identification and control of light polarization. Along with high carrier mobility, nonlinear optical properties, and integration capability due to its layered lattice structure, black phosphorus manifests itself as a promising multipurpose material for chip-scale optoelectronics. In this manuscript, we review the research on black phosphorus photonics, with a focus on the most fundamental active functions in photonic circuits: photodetection, electro-optic modulation, light emission, and laser pulse generation, aiming at evaluating the feasibility of integrating these black phosphorus-based components as a compact system for on-chip applications. [ABSTRACT FROM AUTHOR]

Two-dimensional black phosphorus (BP) holds great promise for future nanoscale field-effect transistors owing to its finite bandgap and expected high carrier mobility. Nevertheless, while most studies have reported unipolar p-type or ambipolar BP transistors with a hole conduction dominance, excellent n-type transport in BP has been a critical challenge. Here, we report unipolar n-type BP transistors realized by a MgO capping layer via atomic layer deposition. By coverage with 20-nm-thick MgO, remarkable electron conduction is obtained in transistors fabricated on BP flakes of thicknesses from 2.6 to 7.6 nm, accompanied by fully suppressed hole transport. Furthermore, the unipolar electron transport is found to retain (or even improve) after a period of six months, with the highest extrinsic electron mobility reaching 135.9 cm2/Vs. The effective approach to realizing unipolar n-FETs of BP demonstrated in this letter paves the way to the implementation of BP-based CMOS digital logic circuits. [ABSTRACT FROM AUTHOR]

This paper demonstrates a high-performance black phosphorus nanoribbons field-effect transistor (BPNR-FET) and systematically investigates methods for enhancing its anisotropic carrier transport. The BPNR-FET shows a strong dependence on crystal orientation in which the best mobility performance is achieved in armchair-oriented nanoribbons. A downscaling of nanoribbon width is shown to improve the short-channel effect owing to a better electrostatic gate control. Furthermore, hydrogenation is employed to effectively passivate the dangling bonds and heal the nanoribbon edge defects, leading to nearly hysteresis-free transfer properties. By virtue of bandgap and contact-metal workfunction engineering, n-type BPNR-FET is successfully demonstrated, which enables complementary inverter circuits to be simultaneously realized. This paper unravels the superior performance underscores a conceptually new BPNR-FET, paving the way toward the development of non-planar devices and integrated circuits based on 2-D materials platform. [ABSTRACT FROM AUTHOR]

Abstract: Achieving excellent electrostatic control and immunity to short channel effects are the formidable challenges in ultrascaled devices. 3D device architectures, such as nanoribbon, have successfully mitigated these problems by achieving uniform top‐ and side‐wall control of the channel. Here, by leveraging on the merits of 3D structure, high‐mobility black phosphorus nanoribbon field‐effect transistors (BPNR‐FET) are demonstrated and the anisotropic transport properties are systematically investigated. A simple top‐down reactive ion etching method is used to realize both armchair‐ and zigzag‐oriented nanoribbons with various widths down to 60 nm. The mobility of BPNR‐FET is found to be width‐ and thickness‐dependent, with the highest hole mobility of ≈862 cm2 V−1 s−1 demonstrated in armchair‐oriented device at room temperature by combining high‐κ gate dielectric and hydrogen treatment to reduce sidewall scattering. Furthermore, hydrogenation effectively passivates the nanoribbon dangling bonds, leading to hysteresis and contact resistance improvement. This work unravels the superior electrical performance underscore a conceptually new device based on BP nanoribbons, paving the way toward the development of nonplanar devices on 2D materials platform. [ABSTRACT FROM AUTHOR]

2D layered materials based p-n junctions are fundamental building block for enabling new functional device applications with high efficiency. However, due to the lack of controllable doping technique, state-of-the-art 2D p-n junctions are predominantly made of van der Waals heterostructures or electrostatic gated junctions. Here, the authors report the demonstration of a spatially controlled aluminum doping technique that enables a p-n homojunction diode to be realized within a single 2D black phosphorus nanosheet for high performance photovoltaic application. The diode achieves a near-unity ideality factor of 1.001 along with an on/off ratio of ≈5.6 × 103 at a low bias of 2 V, allowing for low-power dynamic current rectification without signal decay or overshoot. When operated under a photovoltaic regime, the diode's dark current can be significantly suppressed. The presence of a built-in electric field additionally gives rise to temporal short-circuit current and open-circuit voltage under zero external bias, indicative of its enriched functionalities for self-powered photovoltaic and high signal-to-noise photodetection applications. [ABSTRACT FROM AUTHOR]

Double-gate FinFET (\110)\langle \110\rangle and (\100)\langle \100\rangle electron mobility (\mue) and hole mobility (\muh) are experimentally investigated for the following: 1) a wide range of boron and phosphorus fin doping concentrations and 2) a wide variety of gate stacks combining \HfO2, \SiO2, or SiON insulators with TiN or poly-Si electrodes. It is found out that, irrespective of fin doping and gate stack, (\110)\langle\110\rangle\ \mue is competitive with the (\100)\langle\100\rangle\ \mue, while (\110)\langle\110\rangle\ \muh is \geq \2 \times higher than (\100)\langle\100\rangle\ \muh. Inversion \mue and \muh are independent of doping as long as the effective field/doping combination enables the screening of the depletion charge. Mobility degradation with doping is significantly lower in accumulation mode (AM) than in inversion mode (IM) such that, for heavily B-doped fins, AM hole mobility exceeds the IM electron mobility even in (100) FinFETs. In undoped fins, ALD TiN gate stress is observed to improve \mue  for both orientations without degrading \muh. [ABSTRACT FROM AUTHOR]

The rediscovery of graphene in the recent past has propelled the rapid development of exfoliation and other thin layer processing techniques, leading to a renewed interest in black phosphorus (BP). Since 2014, BP has been extensively studied due to its superior electronic, photonic, and mechanical properties. In addition, the unique intrinsic anisotropic characteristics resulting from its puckered structure can be utilized for designing new functional devices. In retrospect, significant efforts have been directed toward the synthesis, basic understanding, and applications of BP in the fields of nanoelectronics, ultrafast optics, nanophotonics, and optoelectronics. Here, the recent development of BP‐based devices, such as nanoribbon field‐effect transistors, complementary logic circuits, memory devices, and the progress made in meeting the challenges associated with contact resistance, in‐plane anisotropy, and advanced gate stack, are reviewed. Finally, the prospects of 2D materials in meeting the International Technology Roadmap for Semiconductor requirements for the year 2030 are discussed. The recent development of black phosphorus based electronic devices, such as nanoribbon field‐effect transistors, complementary logic circuits, memory, and the progress made in meeting the challenges associated with contact resistance, in‐plane anisotropy, and advanced gate stack are reviewed. The prospects of 2D materials in meeting the International Technology Roadmap for Semiconductor requirements for the year 2030 are also discussed. [ABSTRACT FROM AUTHOR]