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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]

Highlights: State-of-the-art research on two-dimensional material-based memristive arrays is comprehensively reviewed. Critical steps in achieving in-memory computing are identified and highlighted, covering material selection, device performance analysis, and array structure design. Challenges in progressing from single-device characterization to array-level and system-level implementations are discussed, along with proposed solutions. The conventional computing architecture faces substantial challenges, including high latency and energy consumption between memory and processing units. In response, in-memory computing has emerged as a promising alternative architecture, enabling computing operations within memory arrays to overcome these limitations. Memristive devices have gained significant attention as key components for in-memory computing due to their high-density arrays, rapid response times, and ability to emulate biological synapses. Among these devices, two-dimensional (2D) material-based memristor and memtransistor arrays have emerged as particularly promising candidates for next-generation in-memory computing, thanks to their exceptional performance driven by the unique properties of 2D materials, such as layered structures, mechanical flexibility, and the capability to form heterojunctions. This review delves into the state-of-the-art research on 2D material-based memristive arrays, encompassing critical aspects such as material selection, device performance metrics, array structures, and potential applications. Furthermore, it provides a comprehensive overview of the current challenges and limitations associated with these arrays, along with potential solutions. The primary objective of this review is to serve as a significant milestone in realizing next-generation in-memory computing utilizing 2D materials and bridge the gap from single-device characterization to array-level and system-level implementations of neuromorphic computing, leveraging the potential of 2D material-based memristive devices. [ABSTRACT FROM AUTHOR]

Abstract: This work investigates for the first time, the physics of carrier transport in a sub-90nm strained silicon-on-insulator (SOI) n-MOSFET with silicon–carbon (Si:C) source/drain (S/D) regions. The insertion of Si:C in the S/D exerts a lateral tensile strain in the transistor channel, leading to appreciable drive current enhancement. Significant improvement in both carrier backscattering r sat and source injection velocity υ inj were observed, accounting for the large drive current I Dsat enhancement in Si:C S/D transistors. This improvement becomes more appreciable as the gate length is reduced. The reduction in r sat is related to a shorter critical length ℓ0 for carrier backscattering. On the other hand, the splitting of six-fold degenerate conduction band valleys due to strain-induced effects results in a reduced in-plane transport mass and thus contributes to significant υ inj enhancement. In addition, the dependence of drive current performance on source injection velocity and ballistic efficiency in a short channel MOSFET is also discussed. [Copyright &y& Elsevier]

The authors report on high transverse magnetic (TM)-mode responsivity in a waveguided germanium Schottky-barrier metal-semiconductor-metal photodetector on silicon-on-insulator substrate for operating wavelength at 1550 nm. The employed aluminum interdigitated electrodes act as a one-dimensional rectangular grating above the depletion layer. By means of properly designed finger dimensions, surface plasmon polariton resonances can be excited at the interface of metal and silicon interfacial layer due to grating coupling. The resulting strong field intensities reach into active region, enabling high absorption under TM injection. At a voltage of 1 V, the TM-mode photocurrent is measured over three times than that of transverse electric mode, in spite of the relatively larger TM insertion loss in the silicon waveguide. [ABSTRACT FROM AUTHOR]

The development of all‐in‐one devices for artificial visual systems offers an attractive solution in terms of energy efficiency and real‐time processing speed. In recent years, the proliferation of smart sensors in the growth of Internet‐of‐Things (IoT) has led to the increasing importance of in‐sensor computing technology, which places computational power at the edge of the data‐flow architecture. In this study, a prototype visual sensor inspired by the human retina is proposed, which integrates ferroelectricity and photosensitivity in two‐dimensional (2D) α‐In2Se3 material. This device mimics the functions of photoreceptors and amacrine cells in the retina, performing optical reception and memory computation functions through the use of electrical switching polarization in the channel. The gate‐tunable linearity of excitatory and inhibitory functions in photon‐induced short‐term plasticity enables to encode and classify 12 000 images in the Mixed National Institute of Standards and Technology (MNIST) dataset with remarkable accuracy, achieving ≈94%. Additionally, in‐sensor convolution image processing through a network of phototransistors, with five convolutional kernels electrically pre‐programmed into the transistors is demonstrated. The convoluted photocurrent matrices undergo straightforward arithmetic calculations to produce edge and feature‐enhanced scenarios. The findings demonstrate the potential of ferroelectric α‐In2Se3 for highly compact and efficient retinomorphic hardware implementation, regardless of ambipolar transport in the channel. [ABSTRACT FROM AUTHOR]

Spatial‐temporal time series analysis and forecasting are crucial for understanding dynamic systems and making informed decisions. Recurrent neural networks (RNNs) have paved the way for reservoir computing (RC), a method enabling effective temporal information processing at low training costs. While software‐based RC performs well, physical RC systems face challenges like slow processing speed and limited state richness, leading to high hardware costs. This study introduces an innovative approach, i.e., the antiferroelectric field effect transistor‐based RC (AFeFET‐based RC) system for efficient temporal data processing. By exploiting the fading memory property inherent in hafnium oxide‐based antiferroelectric material, this system demonstrates promise for physical RC implementation. Moreover, it leverages the light sensitivity of 2D molybdenum disulfide (MoS2) channels for controllable temporal dynamics under electrical and optical stimuli. This dual‐mode modulation significantly enriches the reservoir state, boosting overall system performance. Experimental tests on standard benchmarking tasks using the AFeFET‐based RC system yielded impressive accuracy results (95.4%) in spoken‐digit recognition and a remarkable normalized root mean square error (NRMSE) of 0.015 in Mackey–Glass time series prediction. [ABSTRACT FROM AUTHOR]

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]

Multi-terminal memtransistors using polycrystalline monolayer molybdenum disulfide (MoS2) have recently emerged as novel synaptic devices. Due to the coexistence of disorder and strong Coulomb carrier-carrier interactions in MoS2, localization and delocalization of carriers can come into play successively upon the relative strength of disorder and interactions, which can be tuned by the Fermi level ( E F ). In this work, we show that the transition from trap-mediated to band-like transport leads to the resistive switching behavior in MoS2 memtransistors, which is driven by the E F shift arising from defect profile redistribution that is facilitated by grain boundaries. In the high resistance state, field-driven hopping conduction can be clearly observed in the high-field region (E > 0.05 MV/cm), whereas the linear dependence of l n (I / E) on the square root of the electric field, E 1 / 2 , suggests Poole–Frenkel emission in the low-field region (E ≤ 0.05 MV/cm). In the low resistance state, strong interactions prevailed and a substantial amount of thermally activated electrons are excited into the conduction band, leading to band-like transport. [ABSTRACT FROM AUTHOR]

The analog resistive switching (RS) characteristics in 2-D polycrystalline (poly-) molybdenum disulfide (MoS2) field-effect transistors (FETs) enable new electronic devices capable of emulating biological synaptic behaviors. In 2-D poly-materials, grain boundary (GB)-induced trap states are of major significance to RS behaviors. However, there is still a lack of appropriate compact models that capture accurate physical mechanisms. Therefore, we developed a surface potential-based compact model, based on the theories of the GB energy barrier and space charge limited current (SCLC). By calibrating to experimental data of MoS2, the physical parameters are extracted, and the model explains the scaling behaviors of channel lengths and grain sizes. Due to the electric-field-induced defect redistribution, the energy barrier modulation at a single-GB (e.g., intersecting GB) quantitatively matches the reported experiments. Moreover, the possible SCLC-based RS behavior is also investigated. Furthermore, we have optimized the set/reset process and simulated the postsynaptic current (PSC) with a tunable potentiation (or depression) process, and then the gate voltage dependence and statistical effects on RS and PSC have been investigated. Thus, this model provides important devices physics insights of 2-D poly-materials and it guides device design, fabrication, and material engineering, to meet the requirements of the future neuromorphic computing application. [ABSTRACT FROM AUTHOR]

In‐memory computing, particularly neuromorphic computing, has emerged as a promising solution to overcome the energy and time‐consuming challenges associated with the von Neumann architecture. The ferroelectric field‐effect transistor (FeFET) technology, with its fast and energy‐efficient switching and nonvolatile memory, is a potential candidate for enabling both computing and memory within a single transistor. In this study, the capabilities of an integrated ferroelectric HfO2 and 2D MoS2 channel FeFET in achieving high‐performance 4‐bit per cell memory with low variation and power consumption synapses, while retaining the ability to implement diverse learning rules, are demonstrated. Notably, this device accurately recognizes MNIST handwritten digits with over 94% accuracy using online training mode. These results highlight the potential of FeFET‐based in‐memory computing for future neuromorphic computing applications. [ABSTRACT FROM AUTHOR]

Artificial synapses in neuromorphic computing systems hold potential to emulate biological synaptic plasticity to achieve brain-like computation and autonomous learning behaviors in non-von-Neumann systems. 2D materials, such as graphene, graphene oxide, hexagonal boron nitride, transition metal dichalcogenides, transition metal oxides, 2D perovskite, and black phosphorous, have been explored to achieve many functionalities of biological synapses due to their unique electronic, optoelectronic, electrochemical, and mechanical properties that are lacking in bulk materials. This review features the current development in the state-of-the-art artificial synaptic electronic devices based on 2D materials. The structures of these devices are first discussed according to their number of terminals (two-, three-, four-, and multi-terminals) and geometric layouts (vertical, horizontal, hybrid). Since different 2D materials have been utilized to fabricate these devices, their underlying physical mechanisms and principles are further discussed, and their artificial neuron synaptic functionalities and performances are analyzed and contrasted. Finally, a summary of the current research status and major achievements is concluded, and the outlooks and perspectives for this emerging and vibrant field and the potential applications of these devices for neuromorphic computing are presented. [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]

2D semiconductor field‐effect transistors (2D FETs) have emerged as a promising candidate for beyond‐silicon electronics applications. However, its device performance has often been limited by the metal‐2D semiconductor contact, and the non‐negligible contact resistance (RSD) not only deteriorates the on‐state current but also hinders the direct characterization of the intrinsic properties of 2D semiconductors (e.g., intrinsic charge carrier mobility, μint). Therefore, a proper extraction technique that can independently characterize the metal‐2D semiconductor contact behavior and the intrinsic properties of a 2D semiconducting layer is highly desired. In this study, a universal yet simple method is developed to accurately extract the critical parameters in 2D FETs, including characteristic temperature (To), threshold voltage (VT), RSD, and μint. The practicability of this method is extensively explored by characterizing the temperature‐dependent carrier transport behavior and the strain‐induced band structure modification in 2D semiconductors. Technology computer aided design simulation is subsequently employed to verify the precision of RSD extraction. Furthermore, the universality of the proposed method is validated by successfully implementing the extraction to various 2D semiconductors, including black phosphorus, indium selenide, molybdenum disulfide, rhenium disulfide, and tungsten disulfide with top‐ and bottom‐gated configurations. [ABSTRACT FROM AUTHOR]

Substitutional and adatom impurity doping can be considered quite effective or even better for modulating the electronic transport coefficients. Herein, we have studied the impact of substitutional doping by Al and Cl multi atoms and adatom adsorption by O, Cu, K, and Ag atoms on the electronic transport properties of single-layer black phosphorus using the first-principles method based density functional theory framework in conjunction with Boltzmann transport equation at room temperature. We found that these impurity atoms introduce new donor and acceptor induced eigenstates and flat bands within the fundamental bandgap. We have calculated the scattering rates and relaxation time by solving the Boltzmann transport equation with the ab-initio calculated electron-phonon interactions. The electron-phonon coupling matrix elements are computed through maximally localized Wannier functions and density functional perturbation theory using Wannier-Fourier interpolation on a fine sampling of the Brillouin zone. The binding energies illustrated the structural stability of all doped systems and found that phosphorene showed a stronger adsorption capability as compared with the graphene and MoS 2 sheet. Moreover, binding energy for the substitutionally doped system is found to decrease with the increasing atomic number. Furthermore, the achieved electron mobility, electrical conductivity (σ), and Seebeck coefficient (S) of pristine single-layer black phosphorus are ~279 cm2V−1s−1, 6.1 × 106 Ω−1m−1 and 1.4 mV/K respectively. The calculated values of carrier mobility, electrical conductivity and Seebeck coefficient have found a rich diversity in each impurity doped layer, and the negative differential behaviour is observed. These results provide comprehensive information about chemical functionalization and bandgap tunability for modelling of phosphorene based devices. • Substitutional and adatom impurity doping are effective for modulating the electronic transport coefficients of phosphorene. • We have studied the impact of substitutional doping by Al and Cl multi atoms and adatom adsorption by O, Cu, K, and Ag atoms. • We have calculated the scattering rates and relaxation time by solving the Boltzmann transport equation. • The binding energies illustrated the structural stability and found that phosphorene showed a stronger adsorption capability. • The calculated values of carrier mobility, electrical conductivity and Seebeck coefficient have found a rich diversity. [ABSTRACT FROM AUTHOR]

In this article, a β-Ga2O3 metal-interlayer-semiconductor Schottky barrier diode (MIS-SBD) using Al-reacted aluminum oxide as the interlayer is demonstrated for the first time and compared with conventional metal-semiconductor (MS) Schottky barrier diode (SBD). The aluminum oxide is formed by sputtering a thin Al layer on Ga2O3 substrate and then annealed in O2 at 300 °C. With the insertion of Al-reacted interlayer, the SBD subthreshold swing (SS) is significantly improved to 61 mV/dec with an average current range of > 6 orders. Example of atomic layer deposited (ALD) Al2O3 as the interlayer is also fabricated and characterized. J – V study corrected by Gaussian distribution model shows that all the samples statistically exhibit similar mean barrier heights (BHs). This indicates that the interlayer hardly affects the electrostatic field and band bending as experienced by carrier injections. C – V study provides different BH results in different sample setups. The result proves that Al-reacted interfacial layer helps eliminate interface degradation as compared with ALD Al2O3. Overall, MIS-SBD by Al-reaction method exhibits improved SS, reduced reverse leakage current (I0), low ideality factor, good ON-OFF ratio (> 109), and minimized interface charges as compared with its respective counterparts. The result of this article serves as a promising interface engineering technique for Ga2O3-based SBD designs. [ABSTRACT FROM AUTHOR]

This article presents an analytical method for parameter extraction in oxide semiconductor field-effect transistors (OS FETs), including threshold voltage (VT), effective channel length (Leff), source–drain series resistance (RSD), and intrinsic effective mobility (μint). An analytical expression of effective mobility (μeff) is implemented with the consideration of percolation conduction and RSD effects. This method relies on the concept of Y-function method and the channel length dependent measurement. The extraction results are compared to those from the combination of transfer length method (TLM). It has been shown that a better accuracy of the extracted parameters is achieved with the proposed method. Furthermore, transfer characteristics are resimulated based on the extracted parameters, in which a good match between measurement and simulation is obtained. [ABSTRACT FROM AUTHOR]

• A novel carbon allotrope T 5 -carbon is predicted by using first-principles calculations. It has a Vickers hardness of 76.5 GPa, which is lower than that of diamond but larger than those of T-carbon and cubic boron nitride. The reason for the slight lower Vickers hardness of T 5 -carbon in comparison with diamond can be ascribed to the weaker bonding strengths in the carbon tetrahedron. A novel carbon allotrope is predicted by first-principles calculations. This allotrope is obtained by replacing one of the two atoms in the primitive cell of diamond with a carbon tetrahedron, thus it contains five atoms in one primitive cell, termed T 5 -carbon. The stabilities of T 5 -carbon are checked in structural, thermal and vibrational calculations. T 5 -carbon is a wide band gap semiconductor with an indirect band gap of 4.30 eV, and has a lattice thermal conductivity of 409 W/mK. Mechanical analyses reveal that T 5 -carbon shows good mechanical performances. Furthermore, by modifying T 5 -carbon with replacing some carbon atoms with Si or Ti atoms, we can obtain SiC 4 or TiC 4 structures. Importantly, the TiC 4 system has a moderate conduction and valance band edges, comparable larger absorption capacity of visible light and smaller effective masses of electron and hole carriers than TiO 2 , confirming its photocatalysis applications. [ABSTRACT FROM AUTHOR]

Black phosphorus (BP) offers unique opportunities for mid‐infrared (MIR) waveguide photodetectors due to its narrow direct bandgap and layered lattice structure. Further miniaturization of the photodetector will improve operation speed, signal‐to‐noise ratio, and internal quantum efficiency. However, it is challenging to maintain high responsivities in miniaturized BP waveguide photodetectors because of reduced light–matter interaction lengths. To address this issue, a method utilizing the slow light effect in photonic crystal waveguides (PhCWGs) is proposed and experimentally demonstrated. A shared‐BP photonic system is proposed and utilized to fairly and precisely characterize the slow light enhancement. Close to the band edge around 3.8 µm, the responsivity is enhanced by more than tenfold in the BP photodetector on a 10 µm long PhCWG as compared with the counterpart on a subwavelength grating waveguide. At a 0.5 V bias, the BP PhCWG photodetector achieves a 11.31 A W−1 responsivity and a 0.012 nW Hz−1/2 noise equivalent power. The trap‐induced photoconductive gain is validated as both the dominant photoresponse mechanism and the major limiting factor of the response speed. The BP slow light waveguide photodetector is envisioned to realize miniaturized high‐performance on‐chip MIR systems for widespread applications including environmental monitoring, industrial process control, and medical diagnostics. [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]

Monolayer W xMo1− xS2-based field effect transistors are demonstrated for the first time on the monolayer W xMo1− xS2 flake, which is grown by the chemical vapor deposition method under an atmospheric pressure. Detailed material studies using Raman and photoluminescence measurements have been carried out on the as-grown monolayer W xMo1− xS2. Electronic band structure of monolayer W xMo1− xS2 has been calculated using first-principle theory. The thermal stability of monolayer W xMo1− xS2 has been evaluated using Raman-temperature measurement. Carrier transport study on the fabricated W xMo1− xS2 FETs has been analyzed using temperature-dependent current measurement, and a field effect mobility of ≈30 cm2 V−1 s−1 at 300 K is obtained. [ABSTRACT FROM AUTHOR]

High-resolution x -ray photoelectron spectroscopy (XPS) was employed to characterize the energy band alignment between TiO 2 /multilayer (ML)-MoS 2 . The TiO 2 film and ML-MoS 2 film was grown by an atomic layer deposition (ALD) and chemical vapor deposition (CVD), respectively. The effect of CHF 3 plasma treatment on the band alignment between TiO 2 /ML-MoS 2 was evaluated. It was found that the valence band offset (VBO) and a conduction band offset (CBO) of TiO 2 /ML-MoS 2 interface was changed from 2.28 eV to 2.51 eV, and from 0.28 eV to 0.51 eV, respectively for the sample with CHF 3 plasma treatment. With the CHF 3 plasma treatment, the down-shift of Mo 3d core level binding energy results in a bend-up of energy potential on the MoS 2 side, leading to 0.23 eV ΔE C difference between the control and the sample with CHF 3 plasma treatment, which is caused by the interfacial layer in rich of F element. The physics details of the band alignment at TiO 2 /ML-MoS 2 interface will provide a guide for the MoS 2 based electronic device design. [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]

Correction to: I Scientific Reports i https://doi.org/10.1038/s41598-022-22913-7, published online 26 October 2022 In the original version of this Article, Kah-Wee Ang and Yong-Wei Zhang were omitted as corresponding authors. Correspondence and requests for materials should also be addressed to kahwee.ang@nus.edu.sg and zhangyw@ihpc.a-star.edu.sg The original Article has been corrected. [Extracted from the article]

The energy band alignment between Al 2 O 3 /multilayer (ML)-MoS 2 was characterized using high-resolution x -ray photoelectron spectroscopy (XPS). The Al 2 O 3 was deposited using an atomic layer deposition (ALD) tool. A valence band offset of 4.10 eV and a conduction band offset of 3.41 eV were obtained across the ALD-Al 2 O 3 /ML-MoS 2 interface. For comparison, the valence band offset and a conduction band offset were also obtained for ALD-SiO 2 /ML-MoS 2 interface. It was found out that ALD-Al 2 O 3 /ML-MoS 2 interface has a larger conduction band offset, compared to that of ALD-SiO 2 /ML-MoS 2 interface, which indicate ALD-Al 2 O 3 served as the gate dielectric for n-type ML-MoS 2 based field effect transistors has advantage over ALD-SiO 2 in term of suppressing the gate leakage current. [ABSTRACT FROM AUTHOR]

Abstract: Photoresist (PR) trimming for narrowing gate critical dimensions (CD) to sub-50 nm range is a known technique in polysilicon gate CMOS technology. However, the trend to replace polysilicon by a suitable metal such as TaN involves replacement of PR mask by a dielectric hard mask (HM) for providing tight CD and profile control in subsequent TaN etching. We have found that traditional selective etching of dielectrics on top of TaN film poses many challenges. Besides, PR trimming also should be tuned so that PR mask after trimming could match requirements of HM etching. By study and optimization of both PR trimming and HM etching in dipole ring magnetron etcher, we developed a production worthy processes for fabrication of sub-50 nm hard mask used for TaN gate etching in CMOS technology. [Copyright &y& Elsevier]

2D transition metal dichalcogenide (TMD)‐based phototransistors generally work under photoconductive, photovoltaic, or photogating mode, in which photocarriers are generated from band‐to‐band excitation. Nevertheless, due to the relatively large bandgap, most TMD phototransistors working under these modes are restricted in visible spectrum. Here, photodetection in 2D multilayer rhenium disulfide (ReS2) transistor via bolometric mode, which relies on light heating induced conductance change instead of band‐to‐band photoexcitation is reported, making it possible for sub‐bandgap photon detection. The bolometric effect induced photoresponse is first revealed by an anomalous sign switching of photocurrent from positive to negative while increasing gate voltage under visible light, which is further validated by the temperature dependent electrical transport measurements. The phototransistor exhibits remarkable photoresponse under infrared regime, beyond the optical bandgap absorption edge of the ReS2 flake. Additionally, it demonstrates a low noise equivalent power, less than 5 × 10−2 pW Hz−1/2, which is very promising for ultra‐weak light detection. Moreover, the response time is below 3 ms, nearly 3–4 orders of magnitude faster than previously reported ReS2 photodetectors. The findings promise bolometric effect as an effective photodetection mode to extend the response spectrum of large bandgap TMDs for novel and high‐performance broadband photodetectors. [ABSTRACT FROM AUTHOR]

Neuromorphic computing, which emulates the biological neural systems could overcome the high‐power consumption issue of conventional von‐Neumann computing. State‐of‐the‐art artificial synapses made of two‐terminal memristors, however, show variability in filament formation and limited capacity due to their inherent single presynaptic input design. Here, a memtransistor‐based artificial synapse is realized by integrating a memristor and selector transistor into a multiterminal device using monolayer polycrys‐talline‐MoS2 grown by a scalable chemical vapor deposition (CVD) process. Notably, the memtransistor offers both drain‐ and gate‐tunable nonvolatile memory functions, which efficiently emulates the long‐term potentiation/depression, spike‐amplitude, and spike‐timing‐dependent plasticity of biological synapses. Moreover, the gate tunability function that is not achievable in two‐terminal memristors, enables significant bipolar resistive states switching up to four orders‐of‐magnitude and high cycling endurance. First‐principles calculations reveal a new resistive switching mechanism driven by the diffusion of double sulfur vacancy perpendicular to the MoS2 grain boundary, leading to a conducting switching path without the need for a filament forming process. The seamless integration of multiterminal memtransistors may offer another degree‐of‐freedom to tune the synaptic plasticity by a third gate terminal for enabling complex neuromorphic learning. [ABSTRACT FROM AUTHOR]

A high performance photodetector array on transparent substrate is highly sought after for enabling next‐generation imaging technology at the visible wavelengths. 2D materials such as molybdenum disulfide (MoS2) are attractive for such application owing to its superior optoelectronic properties and transparency when scaled to atomic thinness. Here, direct growth of MoS2 on centimeter‐scale transparent Al2O3 substrate is reported using a high yield and scalable chemical vapor deposition approach. This enables a large area photodetector array to be demonstrated, wherein aluminum split bull eye (SBE) plasmonic structure is integrated to achieve further performance boost due to surface plasmon resonance (SPR) effect. For a wavelength of 405 nm, the plasmonic MoS2 detector achieves an ultralow noise equivalent power of ≈6.2 × 10–14 W Hz−1/2 and a high responsivity of 7.26 A W−1 at a small bias of 1.0 V, which is more than 6× larger than the reference detector due to SPR effect. Finite‐difference time‐domain simulation confirms a higher concentration of optical field distribution at the center of the SBE structure, which is responsible for the enhancement of photocurrent and sensitivity even at low‐light condition. A large‐scale transparent MoS2‐on‐Al2O3 plasmonic photodetector array featuring split bull eye structure is demonstrated using CMOS‐compatible aluminum as the plasmonic metal. The split bull eye plasmonic photodetector shows the highest achievable responsivity of 7.26 A W−1 at 405 nm wavelength for a small bias of 1.0 V, which is ≈3× and 6× higher than the reference detector due to surface plasmon resonance effect. [ABSTRACT FROM AUTHOR]

Two-dimensional layered semiconductors such as molybdenum disulfide (MoS2) at the quantum limit are promising material for nanoelectronics and optoelectronics applications. Understanding the interface properties between the atomically thin MoS2 channel and gate dielectric is fundamentally important for enhancing the carrier transport properties. Here, we investigate the frequency dispersion mechanism in a metal-oxide-semiconductor capacitor (MOSCAP) with a monolayer MoS2 and an ultra-thin HfO2 high-k gate dielectric. We show that the existence of sulfur vacancies at the MoS2-HfO2 interface is responsible for the generation of interface states with a density (Dit) reaching ~7.03 × 1011 cm−2 eV−1. This is evidenced by a deficit S:Mo ratio of ~1.96 using X-ray photoelectron spectroscopy (XPS) analysis, which deviates from its ideal stoichiometric value. First-principles calculations within the density-functional theory framework further confirms the presence of trap states due to sulfur deficiency, which exist within the MoS2 bandgap. This corroborates to a voltage-dependent frequency dispersion of ~11.5% at weak accumulation which decreases monotonically to ~9.0% at strong accumulation as the Fermi level moves away from the mid-gap trap states. Further reduction in Dit could be achieved by thermally diffusing S atoms to the MoS2-HfO2 interface to annihilate the vacancies. This work provides an insight into the interface properties for enabling the development of MoS2 devices with carrier transport enhancement. [ABSTRACT FROM AUTHOR]