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We report complementary metal‐oxide semiconductor (CMOS)‐compatible, negative capacitance (NC) ferroelectric (FE) zirconium‐aluminum oxide (ZAO)/ZnO thin‐film transistors (TFTs) at a low thermal budget of 360 °C. The NC‐FE‐TFTs demonstrate uniform device‐to‐device performances, featuring a high memory window of 6.7 ± 0.1 V and steep subthreshold swing of 43 ± 4 mV dec–1. The observation of negative differential resistance at room temperature confirms the NC effect in FE‐ZAO/ZnO TFTs. In addition, a learning accuracy of ≈92% is achieved, highlighting the potential for high precision neuromorphic computing application. [ABSTRACT FROM AUTHOR]

Negative differential resistance (NDR) is of considerable interest due to the uncommon characteristic of having a region where the current decreases as the applied voltage bias increases. However, it is difficult to reproduce NDR devices and evaluate their reliability and stability because of the unstable NDR behaviors. In this paper, a highly stable photo‐induced hybrid photonic (HP)‐NDR device is presented for practical applications, which has heterostructure between TiO2‐x nanorods formed by oblique angle deposition and dinaphtho[2,3‐b:2′,3′‐f]‐thieno[3,2‐b]thiophene. The mechanism of NDR behaviors is investigated through morphological analysis, energy band structure, and electrical characteristics. In addition, diverse bias stress and endurance measurements are performed to demonstrate the reliability of the HP‐NDR device. As a result, the NDR behavior lasts up to 1,000 s in each bias stress and 38,850 cycles in the repeated current–voltage (I–V) characteristics Thus, the study has successfully achieved robust HP‐NDR devices with potential for practical applications. [ABSTRACT FROM AUTHOR]

The transport properties of molecular devices based on carbon chains are systematically investigated using a combination of non-equilibrium Green's function (NEGF) and density functional theory (DFT) first-principle methods. In single-carbon-chain molecular devices, a distinct even–odd behavior of the current emerges, primarily influenced by the density of states (DOS) within the chain channel. Additionally, linear, monotonic currents exhibit Ohmic contact characteristics. In ladder-shaped carbon-chain molecular devices, a notable current stabilization behavior is observed, suggesting their potential utility as current stabilizers within circuits. We provide a comprehensive analysis of the transport properties of molecular devices featuring ladder-shaped carbon chains connecting benzene-ring molecules. The occurrence of negative differential resistance (NDR) in the low-bias voltage region is noted, with the possibility of manipulation by adjusting the position of the benzene-ring molecule. These findings offer a novel perspective on the potential applications of atom chains. [ABSTRACT FROM AUTHOR]

Based on density functional theory (DFT) and nonequilibrium Green's function (NEGF) framework, to study the monolayer (ML) blue phosphorene (BlueP) doped with C along zigzag direction, such as the structural stability, and electronic and transport properties. Interestingly, we found that doping engineering strategies can effectively transform monolayer ML ZBlueP doped with C into a spintronic nanodevice with a few unique transport properties. Firstly, our model showed a magnificently giant magnetoresistance (GMR) up to 10 $ ^4 $ 4 under low bias. Secondly, a rectifier with a large rectification ratio (RR) of 10 $ ^5 $ 5 was observed. Lastly, negative differential resistance with a peak-to-valley current ratio (PVCR) of 10 $ ^4 $ 4 was observed. Our research shows a promising route towards the development of high-performance ML ZBlueP spintronics technology by doping with C atom. Our results indicate that our models have immense potential for application in nanoscale spintronic devices. [ABSTRACT FROM AUTHOR]

Tunneling-based static random-access memory (SRAM) devices have been developed to fulfill the demands of high density and low power, and the performance of SRAMs has also been greatly promoted. However, for a long time, there has not been a silicon based tunneling device with both high peak valley current ratio (PVCR) and practicality, which remains a gap to be filled. Based on the existing work, the current manuscript proposed the concept of a new silicon-based tunneling device, i.e., the silicon cross-coupled gated tunneling diode (Si XTD), which is quite simple in structure and almost completely compatible with mainstream technology. With technology computer aided design (TCAD) simulations, it has been validated that this type of device not only exhibits significant negative-differential-resistance (NDR) behavior with PVCRs up to 106, but also possesses reasonable process margins. Moreover, SPICE simulation showed the great potential of such devices to achieve ultralow-power tunneling-based SRAMs with standby power down to 10−12 W.

We propose a novel structure for the Esaki tunnel diode that utilizes a quantum well in order to increase the peak-to-valley current ratio. The quantum well is formed by sandwiching a thin layer of GaP between the Si and Ge layers, which creates a potential barrier for carriers. The quantum well enhances the tunneling probability of carriers, resulting in a higher peak current while the valley current remains low; which in total results in a superior peak-to-valley current ratio. We achieve a peak-to-valley current ratio significantly higher than those of conventional heterojunction structures, almost 3.8 fold of them. We use ATLAS TCAD for simulations, which can accurately calculate band-to-band tunneling current. [ABSTRACT FROM AUTHOR]

This paper presents hybrid design of a Ternary Inverter (TI) circuit by integrating an Ovonic-Threshold-Switching (OTS) based Phase-Change-Memory (PCM) cell between Complementary-Metal-Oxide-Semiconductor (CMOS) transistors. Volatile OTS behaviour of the PCM structure helps to generate the ternary state. Reliability of the proposed TI design has been demonstrated through the Monte-Carlo simulations in Cadence-Spectre simulator incorporating both Process and Mismatch variability at all corners. The proposed inverter cell consumes 10.44 $\mu$ W power and 1.47 ns delay on UMC-180 nm technology node. Moreover to demonstrate the scaling potential, we have simulated the proposed inverter at various technology nodes i.e 180/90/65/28 nm. At advanced feature sizes, power and delay are improved by significant amount. For benchmarking, we have compared the proposed TI design with various state-of-the-art hybrid structures. Furthermore, to demonstrate potential applications, we designed and simulated ternary universal logic gates i.e NAND/NOR. Benefits of the proposed TI in circuit applications are shown through a Ternary Multiplier (TMUL) arithmetic circuit implementation. Finally, a Ternary-Static-Random-Access-Memory (TSRAM) is proposed with two back-to-back connected CMOS-PCM TIs with three bit storing capability. [ABSTRACT FROM AUTHOR]

[Display omitted] The ongoing reduction in the size of electronic devices, interconnect delays have emerged as an important constraint in the overall performance of chips. The time it takes for signals to travel over the interconnecting wires is the cause of these delays, which today frequently exceed the intrinsic delays that are present within the integrated circuits (ICs) themselves. The rate at which current chips operate and their overall efficiency are both significantly influenced by this trend. This research investigates the electrical and electronic properties of a device constructed from doped graphene nanoribbons. The device is analyzed under conditions of minimal applied bias or electric field. It features a channel consisting of a minimal unit cell from a zigzag nanoribbon, situated between two zigzag graphene nanoribbons (ZGNR) which function as the electrodes on the left and right sides. The doping process improves the thermodynamic and structural stability of the device, achieving notably low values for total energy, formation energy, and binding energy. By incorporating nitrogen and boron atoms into specific interstitial sites within the ZGNR, the study aims to enhance understanding of the electronic transport mechanisms involving these dopant atoms and the lattice of the ZGNR. This research explores key semiconductor characteristics of the doped ZGNR-based device, such as negative differential resistance (NDR), peak-to-valley ratio (PVR), and rectification ratio (RR), which are crucial for various electronic applications, including switches, logic circuits, memory storage, amplifiers, and negative resistance oscillators. The device demonstrates a peak-to-valley ratio (PVR) of 92 and a rectification ratio (RR) of 149. Additionally, the device exhibits high dielectric energy storage capacity, with a maximum static dielectric constant of 14.7 and substantial low-energy absorption when nitrogen atoms are incorporated into the electrode region. This suggests potential applications in nanoelectronics and as a dielectric energy storage device operating at low applied bias voltages. [ABSTRACT FROM AUTHOR]

Tunnel FETs (TFETs) are preferable over MOSFETs at lower technology nodes due to their superior performance in the subthreshold region in terms of extremely low off current and low subthreshold swing. However, limitations like low drive current, ambipolarity and unidirectional conductivity hamper the usage of TFET device in designing memory structures such as SRAM. In this paper, a new TFET device called Indium Gallium Arsenide - Silicon Double Pocket Dual Gate TFET (InGaAs-Si DP-DGTFET) is proposed. The proposed design shows a relatively high drive current, ON to OFF current ratio, ON current to gate capacitance ratio, subthreshold swing (SS), and lower threshold voltage. The 7T SRAM cell designed using the proposed TFET device significantly improves the performance in terms of read and write speed when compared to Si-DP-DGTFET based SRAM at a supply voltage of 0.7V. The proposed 7T SRAM cell also includes a TFET based NDR sense amplifier circuit to enhance the read operation for lower power consumption. This makes the proposed device a preferred choice for the application that demands high speed and stability with considerable power loss. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) and nonequilibrium Green’s function (NEGF) framework are used to explore the structural, spin-polarized electronic, and spin-based transport properties of edge-hydrogenated zigzag aluminum nitride nanoribbons (ZAlNNRs). The proposed ZAlNNR is observed to be structurally stable and exhibits half-metallic nature in the magnetic state. The quantum transport property of the proposed two-terminal device model of 1H-AlN-1H demonstrates the bipolar spin-filter characteristics along with giant magnetoresistance (GMR), spin-based peak to valley current ratio (spin-PVCR), and spin-based rectification ratio (spin-RR) of the order of 1015, 1012, and 108, respectively. The calculated GMR and spin-RR of the 1H-AlN-1H device are 107 and 102 times higher than zigzag silicene nanoribbon (ZSiNR) and doped-zigzag graphene nanoribbon (doped ZGNR), respectively. The observed GMR, spin-PVCR, and spin-rectifying behavior of the reported ZAlNNR device could be deployed for multifunctional spintronic device applications. [ABSTRACT FROM AUTHOR]

In this article, we demonstrate a reliable physics-based simulation approach to accurately model high-speed In0.53Ga0.47As/AlAs double-barrier resonant tunneling diodes (RTDs). It relies on the nonequilibrium Green’s function (NEGF) formalism implemented in SILVACO Atlas TCAD quantum simulation package to closely mimic the actual device physics, together with the judicious choice of the material parameters, models, and suitable discretization of the associated epitaxial layer structure. The validity of the approach was proved by comparing simulated data with experimental measurements resulting from fabricated micrometer-sized RTD devices featuring two different epitaxially grown layer stacks. Our results show that the simulation software can correctly compute the peak current density ${J} _{p}$ , peak voltage ${V} _{p}$ , and the valley-to-peak voltage difference $\Delta {V}$ = ${V} _{v} - {V} _{p}$ associated with the negative differential resistance (NDR) region of the RTD heterostructure static current density–voltage (${J}$ – ${V}$) characteristic at room temperature (RT), all of which are key parameters in the design of these devices for use in oscillator circuits. We believe that this work will now help in optimizing the RTD epitaxial structure to maximize its radio-frequency (RF) power performance, accelerating developments in the rapidly evolving RTD technology for emerging applications, including next-generation ultra-broadband short-range wireless communication links and high-resolution imaging systems. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) in conjugation with non-equilibrium Green's function (NEGF) is used to investigate the structural, electronic, and transport properties of the pristine and fluorinated zigzag ZnO nanoribbons (ZnONRs). For the fluorinated nanoribbons, the bond lengths at the edges are increased due to the excessive atomic radius of fluorine (F) relative to hydrogen (H). The stability increases with fluorination at the Zn-rich edge and decreases when F is passivated at the O-rich edge. The structure with fluorination at the Zn-rich edge (F-Zn-ZnONR) is the most stable with a binding energy ( E b ) of about −5.052 eV, and the structure with fluorination at the O-rich edge (F-O-ZnONR) is the least stable with a E b of −4.607 eV. All the structures are semiconducting and the pristine structure has the highest energy band gap ( E g ) of about 0.531 eV followed by the lowest E g of 0.011 eV for the structure with fluorination at both edges (F-ZnO-ZnONR). Partial density of states (PDOS) study depicts that the new energy states introduced closer to the Fermi energy level are due to the F atoms. All the devices except the pristine device exhibit negative differential resistance (NDR) characteristics. A significant NDR mechanism is observed in all the fluorinated ZnONRs. The highest peak-to-valley current ratio (PVCR) of about 1.79 × 10 2 is reported for the F-ZnO-ZnONR device. ZnONRs with the reported NDR behavior can be used for designing the future nanoelectronic devices, oscillators, frequency converters, switches, rectifiers, resonators etc. [ABSTRACT FROM AUTHOR]

A nanometer-scaled resonant tunneling diode based on lateral heterojunctions of armchair graphene and boron nitride nanoribbons, exhibiting negative differential resistance is proposed. Low-bandgap armchair graphene nanoribbons and high-bandgap armchair boron nitride nanoribbons are used to design the well and the barrier region, respectively. The effect of all possible substitutional defects (including BC, NC, CB, and CN) at the interface of graphene and boron nitride nanoribbons on the negative differential resistance behavior of the proposed resonant tunneling diode is investigated. Transport simulations are carried out in the framework of tight-binding Hamiltonians and non-equilibrium Green’s functions. The results show that a single substitutional defect at the interface of armchair graphene and boron nitride nanoribbons can dramatically affect the negative differential resistance behavior depending on its type and location in the structure.

In this article, for the first time, we explained a detailed physical insight for negative differential resistance (NDR) to positive differential resistance (PDR) transition in a ferroelectric (FE)-based negative capacitance (NC) FET and also its dependence on the device terminal voltages. Using extensive well-calibrated TCAD simulations, we have investigated this phenomenon on fully depleted silicon on insulator (FDSOI)-NCFET. The NDR-to-PDR transition occurs due to FE layer capacitance changes from a negative to positive state during channel pinchoff. This, in turn, results in a valley point in the output characteristic (${I}_{DS}$ – ${V}_{DS}$) at which the output resistance is infinite. We also found that we could alter the valley point location by modulating the vertical electric field through the FE layer in the channel pinchoff region using body bias (${V}_{BB}$). The interface oxide charges also impacted the NDR to PDR transition, and a positive interface charge results in faster NDR to PDR transition. Furthermore, we have utilized the modulation in the NDR-to-PDR transition due to ${V}_{BB}$ for designing a current mirror. Results show that the output current (${I}_{OUT}$) variation due to ${V}_{DS}$ reduces from ~8% to ~2% with ${V}_{BB}$. We have also designed a single-stage common source (CS) amplifier and provided design guidelines to achieve a higher gain in the NDR region. The results obtained using a small-signal model of the FDSOI-NCFET demonstrate that ~25% higher gain can be achieved with the discussed design guidelines in the NDR region compared to the transition region of ${I}_{DS}$ – ${V}_{DS}$. We have also explored the device scaling effect on the amplifier gain and found that ~ $2.23\times $ gain can be increased with smaller channel length and higher device width. [ABSTRACT FROM AUTHOR]

Emerging voltage reference generators (VRGs) are of great demand for low-power applications in recent years. However, keeping good linearity for VRGs in deep submicrometer process is still challenging. Negative capacitance field-effect transistor (NCFET) is an emerging device, which has been found with a negative differential resistance (NDR) phenomenon and has the potential to be applied in VRGs to optimize their linearity. Hence, the feasibility of using NCFET in an emerging ultralow-power (ULP) VRG is studied in this work. An empirical formula to describe NCFET’s NDR is proposed and verified by simulation through a compact SPICE model based on the Landau–Khalatnikov (LK) equation. By adjusting the strength of NDR of NCFET, its output differential resistance can be changed and cancel out the positive differential resistance (PDR) of CMOS transistor. Therefore, the proposed NCFET-based VRG achieves higher linearity. The simulation results show that the line regulation of the NCFET-based VRG decreases from 2.25%/V to 0.21%/V ($10\times $). [ABSTRACT FROM AUTHOR]

The structural, electronic, and transport properties of zigzag boron nitride nanoribbons (ZBNNRs) with nitrogen-vacancy (N-vacancy) at the center (N-V@C), at the edge (N-V@E), and at the center as well as edge (N-V@CE) are investigated. This work deploys density functional theory (DFT) along with non-equilibrium Green's function (NEGF) formalism. Present DFT-based calculations reveal that a metallic/semiconducting nature can be obtained in N-vacancy ZBNNRs via selective H-passivation. The most structurally stable structure in N-vacancy ZBNNRs is observed for HBN-NV E irrespective of ribbon width. The current–voltage characteristics of pristine, bare, and N-vacancy ZBNNRs devices demonstrated that the bare ZBNNRs exhibit maximum current as compared to the N-vacancy ZBNNRs device under low bias. This is because the vacancy defect breaks the edge states and produces some localized defect-induced states, which suppress the electron transmission and reduces current to get a better I P / I V (peak to valley current ratio PVCR) ratio. It is worth mentioning here that even negative differential resistance (NDR) with a sufficiently high I P / I V ratio has also been observed for BNH-NV E of the order of 10 10 in both positive and negative biasing. The observed NDR effect suggests that selective H-passivation in N-vacancy ZBNNRs has immense potential applications for nanoscale NDR devices. [ABSTRACT FROM AUTHOR]

The development of multifunctional electric device is of great significance for improving the integration dense of integrated circuits in the future. Herein, amorphous WOx-based memristor was fabricated and the mechanism of resistance switching was studied in detail. The device exhibited a stable coexistence of bipolar resistive switching (RS) and negative differential resistance (NDR) behaviors at room temperature, which could modulated by changing the annealing time at 300 °C. The optimal high-resistance state (HRS)/low-resistance state (LRS) resistance ratio of ~30 was obtained by postannealing in 100 min. However, both RS and NDR behaviors disappeared with the crystallization of amorphous films when the annealing time was 300 min. The Ohmic conduction mechanism should be responsible for the charge transport of LRS, while the HRS transmission was corporately dominated by the trap-controlled space charge limited conduction (SCLC) and Poole–Frenkel (P–F) emission. The change of trap levels modulated by postannealing was calculated and considered to be the reason for the change of RS and NDR behaviors. Raman spectroscopy provided evidence for the formation of strong W–O bonds, which contributed to the disappearance of RS and NDR behaviors. [ABSTRACT FROM AUTHOR]

We have considered a graphene nano ribbon-based two probe-device working on the principle of alteration of current-voltage (I–V) characteristic, upon interactions of its channel material with the adsorbed gas molecules. The analysis of sensing parameters alongside the electron transport mechanism was carried out by using density functional theory (DFT) formulated on the Hohenberg-Kohen paradigm in conjunction with the non-equilibrium green functions (NEGF) method. Electronic transport through similar work reported earlier reveals that the combination of these two techniques coordinates extremely well and yields convincing electronic results. The nanoribbon-based sensing device was employed to evaluate its capability to detect Carbon dioxide (CO 2) and Carbon monoxide (CO) molecules. Analysis of the computed result reveals significant modifications in the electronic property of the device upon adsorption of carbon dioxide and carbon monoxide entities on the channel surface. One such significant and dramatic change in the characteristic that we observed is the nature of the channel that transforms from metallic to semi-metallic. Another observed change is the signal amplification capability relative to the pristine device. The signal gets amplified on increasing number of molecular entities from one to six. The transformation in sensor performance is additionally supported by examining variations in multiple parameters, including adsorption energy, charge transfer, differential resistance, and the figure of merit, also known as the peak-to-valley ratio (PVR). The investigation unveiled that the currently designed zigzag graphene nanoribbon (ZGNR) model exhibits high sensitivity to both CO 2 and CO gases. This phenomenon is substantiated by the elevated adsorption energy, increased charge transfer, elevated peak-to-valley ratio (PVR), and heightened sensor response. The substantial sensor response, registering at a magnitude of 8.3, underscores the efficacy of the current system in detecting both low and high concentrations of CO and CO 2 molecules. The current study emphasizes the notion that understanding the electronic and transport behaviour of zigzag graphene nanoribbons (ZGNR) and analogous materials could offer valuable insights for addressing the threat of environmental pollution. • Sensor's sensitivity is tested with varying amounts of carbon oxide molecules. • The modelled sensor exhibits substantial sensitivity to sensing parameters, such as adsorption energy, charge transfer, peak-to-valley ratio (PVR), and sensor response. [ABSTRACT FROM AUTHOR]

Hysteresis and NDR have been observed in the room-temperature current–voltage characteristics of lateral devices featuring planar graphitic electrodes separated by a nitrogen-doped amorphous carbon (a-CNx) layer. The devices were fabricated using energetic physical vapor deposition and electron-beam lithography. Devices formed on a-CNx layers deposited with N2 pressure of 0.10 mTorr exhibited NDR. This NDR occurred at a well-defined voltage/electric field but only after the voltage of the opposite polarity was applied. Based on this behavior, a model is proposed in which the NDR occurs by field-induced trapping/detrapping at one of the graphite/a-CNx interfaces within the device. The results of this investigation highlight the importance of interfaces and defects in determining the characteristics of a-C memristive devices. [ABSTRACT FROM AUTHOR]

The realization of computational circuits in the nanometer scale leads to a higher speed, lower power consumption, and less occupied area on the chip surface in electronic systems. Two of the most important basic logic gates are three-input exclusive-OR (XOR3) and three-input majority (MAJ3) gates which are the two main functions used in designing computational circuits like full-adder (FA) cells. In this article, a new device (molecular transistor) is presented using the naphthalene molecule. The effects of the input terminal variation of the proposed transistor on its output have been studied. According to the results obtained from the simulation, by applying different voltages to the gate-terminal of the transistor (Vg), the negative differential resistance (NDR) behaviors are observed at different intervals of the source-drain voltage (Vsd). Due to the interesting characteristics of the proposed transistor, a full set of three-input basic logic gates is designed and presented. In these gates, a single transistor is utilized and by applying different bias voltages, it can generate different outputs suitable to the intended functions. Besides, an FA cell is designed using the proposed three-input logic gates. The transistor, the gates, and the FA are simulated using nonequilibrium Green’s function (NEGF) and density functional theory (DFT) to verify their functionality. [ABSTRACT FROM AUTHOR]

Abstract Recently, combinations of 2D van der Waals (2D vdW) materials and organic materials have attracted attention because they facilitate the formation of various heterojunctions with excellent interface quality owing to the absence of dangling bonds on their surface. In this work, a double negative differential resistance (D‐NDR) characteristic of a hybrid 2D vdW/organic tunneling device consisting of a hafnium disulfide/pentacene heterojunction and a 3D pentacene resistor is reported. This D‐NDR phenomenon is achieved by precisely controlling an NDR peak voltage with the pentacene resistor and then integrating two distinct NDR devices in parallel. Then, the operation of a controllable‐gain amplifier configured with the D‐NDR device and an n‐channel transistor is demonstrated using the Cadence Spectre simulation platform. The proposed D‐NDR device technology based on a hybrid 2D vdW/organic heterostructure provides a scientific foundation for various circuit applications that require the NDR phenomenon.

To prepare a desired negative differential resistance (NDR) device by standard complementary-metal-oxide-semiconductor (CMOS) process, a photoelectric dual control NDR device with a PNP bipolar-junction-transistor (BJT) and an NPN BJT was designed and fabricated by using the Si-base standard 0.18 μm CMOS process without any process modification and a special substrate. In order to reduce the valley current under optical control, a metal mask was added to the NDR device. The results show that the device exhibits good NDR characteristics under either voltage-control or photo-control. Under voltage-control, a low volley current (0.23 pA) and a high peak-to-valley current ratio (1.4 × 1010) are obtained at less than 1 V. Under photo-control, the two parameters obtained at less than 0.5 V, are 37 nA and 4827, respectively. Also, the device displays fine S-type NDR characteristics and nice maintaining response function under photo-control. These superior photoelectric NDR characteristics endow the device with greatly potential application in the photoelectric logic circuits.

Recently, combinations of 2D van der Waals (2D vdW) materials and organic materials have attracted attention because they facilitate the formation of various heterojunctions with excellent interface quality owing to the absence of dangling bonds on their surface. In this work, a double negative differential resistance (D‐NDR) characteristic of a hybrid 2D vdW/organic tunneling device consisting of a hafnium disulfide/pentacene heterojunction and a 3D pentacene resistor is reported. This D‐NDR phenomenon is achieved by precisely controlling an NDR peak voltage with the pentacene resistor and then integrating two distinct NDR devices in parallel. Then, the operation of a controllable‐gain amplifier configured with the D‐NDR device and an n‐channel transistor is demonstrated using the Cadence Spectre simulation platform. The proposed D‐NDR device technology based on a hybrid 2D vdW/organic heterostructure provides a scientific foundation for various circuit applications that require the NDR phenomenon. [ABSTRACT FROM AUTHOR]

A mathematical model is presented for quantifying the ion number density over a range of discharge current in microplasma discharges. The ion number density is determined from measured discharge voltage, current, pulsing frequency, and trace impurity that is injected into the system deliberately. Experiments are conducted in pure helium with nitrogen being introduced as the trace species. The ion number density is estimated over a range of discharge current and is compared with multidimensional simulation results. [ABSTRACT FROM AUTHOR]

In this paper, we propose a new heterostructure dual material gate junctionless field-effect transistor (H-DMG-JLFET), with negative differential resistance (NDR) characteristic. The drain and channel material are silicon and source material is germanium. The gate electrode near the source is larger. A dual gate material technique is used to achieve upward band bending in order to access n-i-p-n structure which is caused by workfunction difference between electrodes and silicon. In JL-FETs as gate voltage increases, the electric-field intensifies and the band diagram profile starts to change. It is illustrated that, by increasing the gate voltage, the potential barrier decrease and the drain current increase. In the gate voltage of 0.64 V, due to appearance of a negative peak of electric-field and carriers transport within the field, the drain current decrease. Consequently, the NDR characteristic is achieved. With increase of the gate voltage the negative peak of electric-field is intensified and the drain current is decreased. [ABSTRACT FROM AUTHOR]

This paper presents the negative differential resistance (NDR) behavior of an MoS2 armchair nanoribbon double-gate field effect transistor. The large peak-to-valley current ratio (PVCR) of 2.58 × 102 with a peak current value of − 0.8 μA is achieved with the presented device configuration. A 5-nm channel length device was considered for the study and an extended Hückel model with nonequilibrium Green's function method is used for the simulation. A phosphorus atom is used as a substitutional dopant at the sulfur site of the MoS2 field effect transistor near the source and drain regions. The PVCR of the device can be controlled by applying a gate voltage. The achieved subthreshold slope of the device is 88 mV/decade with Ion/Ioff value of 1011 at 300 K. The other parameters such as peak current and NDR voltage window are analyzed. The proposed device configuration shows the potentiality of MoS2 armchair nanoribbon material for future small length scale electronic device applications. [ABSTRACT FROM AUTHOR]

Negative-capacitance field-effect transistors (NCFETs) are emerging devices which have shown huge potential to replace classical field-effect transistors because of their steep switching characteristic enabled by a ferroelectric stack. The negative capacitance in ferroelectrics results in a voltage step-up action which curtails the subthreshold swing below 60 mV/dec. The ferroelectric thickness is a key design parameter which governs the operation of such devices and resulting circuits. We examine herein for the first time the effect of the ferroelectric thickness of undoped HfO2-based negative-capacitance field-effect transistors on the device and circuit performance. Increasing the ferroelectric thickness yields higher gain but with increased probability of hysteresis. Also, depending upon the properties of the underlying transistor, at low overdrive voltage, increase in the ferroelectric thickness beyond a certain value may introduce a loss of saturation (negative differential resistance) in the drain characteristic of the NCFET. Also, we design an NCFET-based resistive load inverter and study the effect of thickness variation on the circuit performance. The results of the analysis show that increasing the thickness within a permissible limit increases the noise margin and reduces the power dissipation of the designed circuit. [ABSTRACT FROM AUTHOR]

We report on high-efficiency, high-power, and low-phase-noise resonant tunneling diode (RTD) oscillators operating at around 30 GHz. By employing a bias stabilization network, which does not draw any direct current (dc), the oscillators exhibit over a tenfold improvement in the dc-to-RF conversion efficiency (of up to 14.7%) compared to conventional designs (~0.9%). The oscillators provide a high maximum output power of around 2 dBm, and low phase noise of −100 and −113 dBc/Hz at 100 kHz and 1 MHz offset frequencies, respectively. The proposed approach will be invaluable for realizing very high efficiency, low phase noise, and high-power millimeter-wave (mm-wave) and terahertz (THz) RTD-based sources. [ABSTRACT FROM AUTHOR]

We study magnetic field control of current through model graphene nanosheet junctions within the framework of the tight-binding approximation. Geometrical asymmetry in the coupling of graphene nanosheets to the contact leads emerges as one of the most important determining factors for the magnetic field control of current. The asymmetric connection split the otherwise degenerate energy levels of the structures leading to energy-resolved transmission peaks which the applied field modulates for a transmission maximum by narrowing the energy gap between the split energy levels. Also, the contact coupling strength plays a decisive role in controlling current in small structures, while its role is significantly less in large structures that have more closely-spaced energy levels. Model calculations on a graphene nanosheet junction with inter-site Coulomb interaction is found to sustain sensitivity to the applied magnetic field. Although several factors bear direct effect on the electron transport through molecular junctions, suitably constructed graphene nanosheet junctions would greatly enhance the prospects of current control under applied magnetic fields. • Magnetic field control of current through the graphene nanosheet junctions is demonstrated. • Geometrical asymmetry in the coupling to the contact leads is crucial. • Coupling strength plays a decisive role in current conduction in small structures. • Magnetic field sensitivity persists even in the presence of Coulomb interaction. • Observed field sensitivity demonstrates its technological relevance in the magnetic sensor applications. [ABSTRACT FROM AUTHOR]

DNA is a self-assembled, double stranded natural molecule that can chelate and align nickel ions between its base pairs. The fabrication of a DNA-guided nickel ion chain (Ni-DNA) device was successful, as indicated by the conducting currents exhibiting a Ni ion redox reaction-driven negative differential resistance effect, a property unique to mem-elements (1). The redox state of nickel ions in the Ni-DNA device is programmable by applying an external bias with different polarities and writing times (2). The multiple states of Ni-DNA-based memristive and memcapacitive systems were characterized (3). As such, the development of Ni-DNA nanowire device-based circuits in the near future is proposed. [ABSTRACT FROM AUTHOR]

Tunneling field-effect transistors (TFETs) have been proposed as energy-efficient switches for low-power integrated circuits. In this letter, we present the first reconfigurable black phosphorus vertical TFET. The device exhibits a record high ON-current (${I}_{\text {ON}}$) among all 2D TFETs of $15.2~\mu \text{A}/\mu \text{m}$ at ${V}_{\text {DS}} = -{1}$ V and a subthreshold swing (SS) of 187 mV/dec at $V_{\text {DS}} = -{0.3}$ V. By tuning the electrostatic doping with multiple gates, the device can be reconfigured to operate in the TFET mode or the MOSFET mode and can be tuned to behave like an n-type or p-type FET. Moreover, negative differential resistance (NDR) is observed in the forward bias of the TFET at room temperature, providing unambiguous evidence of band-to-band tunneling in our devices. [ABSTRACT FROM AUTHOR]

Hexagonal boron nitride encapsulation significantly improves carrier transport in graphene. This paper investigates the benefit of implementing the encapsulation technique in graphene field-effect transistors (GFETs) in terms of their intrinsic radio frequency (RF) performance, adding the effect of the series resistances at the terminals. For such a purpose, a drift-diffusion self-consistent simulator is prepared to get the GFET electrical characteristics. Both the mobility and saturation velocity are obtained by an ensemble Monte Carlo simulator upon considering the relevant scattering mechanisms that affect carrier transport. RF figures of merit are simulated using an accurate small-signal model. Results reveal that the cutoff frequency could scale up to the physical limit given by the inverse of the transit time. Projected maximum oscillation frequencies, in the order of few terahertz, are expected to exceed the values demonstrated by InP and Si-based RF transistors. The existing tradeoff between power gain and stability and the role played by the gate resistance are also studied. High power gain and stability are feasible even if the device is operated far away from current saturation. Finally, the benefits of device unilateralization and the exploitation of the negative differential resistance region to get negative-resistance gain are discussed. [ABSTRACT FROM AUTHOR]

In this paper, we have investigated the electronic transport properties and current–voltage characteristics of the armchair and zigzag $\Upsilon $ -graphyne nanotubes by the SIESTA and TRANSIESTA packages including density functional theory and nonequilibrium Green’s function for the four chiral vectors 2, 3, 4, and 5. We foundthat the current in $\Upsilon $ -graphyne nanotubes is very negligible for low bias voltages, but it enhances precipitously for voltages above the thresholdvoltage. Both zigzag and armchair $\Upsilon $ -graphyne nanotubes reveal negative differential resistance, for specific diameters, which is a promising result for nano-based device usages such as switching and memory circuits. Finally, the characteristics of these nanotubes are similar to those of a two-way tunneling diode. Therefore, we can expect a new application that produces oscillation. [ABSTRACT FROM AUTHOR]

The electronic and transport characteristics of selective edge hydrogenated MgO nanoribbons (MgONRs) are investigated using non-equilibrium Green's function (NEGF) in combination with density functional theory (DFT). The selective edge hydrogenation influences the stability of nanoribbons with bare MgONR (B MgO B) being the most stable structure while the bare O-edge MgONR (H MgO B) is the least stable structure. Irrespective of edge passivation, all the structures are metallic in nature. The transport calculations reveal that the bare Mg-edge (B MgO H) nanoribbon exhibits ohmic current behavior while the other nanoribbons exhibit negative differential resistance (NDR) behavior. The H MgO B device exhibits a significant NDR behavior with a significantly high peak-to-valley current ratio (PVCR) of about 3.07 × 106. Further, the B MgO H device is explored extensively for nanointerconnect performance. The transmission eigenstates illustrate the bare Mg-edge atoms contribute to the flow of carriers in B MgO H device. The parasitic components of the B MgO H device such as quantum capacitance (C Q), kinetic inductance (L K), and quantum resistance (R Q) are measured to be 3.59 fF/ μ m, 37.50 nH/ μ m , 6.46 k Ω , respectively. In addition, the B MgO H interconnects are stable and have excellent delay (τ), power delay product (PDP), and frequency response over copper interconnects. In addition to line resistance and capacitance, crosstalk is proven to degrade the interconnect performance. The obtained findings suggest that the MgONRs can be potentially used to design nanointerconnects and NDR based nanoelectronic device design by tailoring the edge hydrogenation. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Type I organic quantum wells (OQWs) were fabricated in physical sense. • Blueshifts in the optical absorptions of the OQWs were observed. • Negative differential resistance (NDR) behaviors were obtained. Construction of organic quantum wells (OQWs) has been a challenge due to the difficulty in fabricating high-quality organic films in large area. Here, type I OQWs are successfully fabricated by using two OSCs with different bandgaps, and they exhibit both negative differential resistance (NDR) effect and absorption blueshift. Moreover, the OQW photoswitches show much higher photoresponsivity than the corresponding organic heterojunction ones. All the above results prove the successful construction of OQWs in a physical sense. [ABSTRACT FROM AUTHOR]

In recent years, single-element 2-D atom crystal materials have aroused extensive interest in many applications. Blue phosphorus, successfully synthesized on Au (111) substrate by molecular beam epitaxy not long ago, shows unusual geometrical and electronic structures. We investigate the electronic structures and transport properties of zigzag blue phosphorene nanoribbons (ZBPNRs) by using a first-principles method, which can be obviously tuned via different groups (i.e., -H, -O, and -OH) passivation on both edges. The ZBPNRs-H and ZBPNRs-OH present a wide-gap semiconductor property, while the ZBPNRs-O are metallic. Interestingly, the current–voltage (${I}$ – ${V}$) curves of ZBPNRs-O show a negative differential resistive (NDR) effect, which is independent on the ribbon width. The electric current through the ZBPNRs-O mainly flows along both the outside zigzag phosphorus chains through the P-P bond current. By modifying both the edges with various functional groups, the ZBPNRs can display some important functional characteristics and become a candidate of NDR devices. [ABSTRACT FROM AUTHOR]

In this paper, the effect of electron–phonon scattering on the negative differential resistance of graphene nanoribbon p-n junctions is investigated. The results show that the optical phonon scattering, due to inelasticity, significantly increases the valley current such that the peak-to-valley ratio decreases several orders of magnitude compared to ballistic approximation. It also shifts up the valley voltage. The former effect manifests itself more in structures with a smaller band gap and better ballistic characteristics. We show that it remains remarkable in different lengths of the transition region and severely affects the performance of the device. The results also show that phonon scattering plays a significant role even in ultrascaled nanodevices. [ABSTRACT FROM AUTHOR]

In this paper, a detailed derivation process is proposed to characterize the Resonant Tunneling Diode (RTD) for high frequency regime. The proposed model is used to design and analyze a simple microwave oscillator based on the RTD using the commercial circuit simulation software, ADS from Agilent Technologies. The simulation is carried out using different equivalent circuit models; the proposed model, the original constant RC model, and the series/parallel double RC model, which is an alternative to the quantum-inductance RLC model. This is performed in terms of oscillation frequency and output power against resonant circuit elements, considering the CPU time. A comparison between the simulation results of the three models indicates that the proposed model is simple, accurate, and appropriate to investigate the behavior of the RTD at high frequency without any singularity and convergence problems. Also, its complexity (CPU time) is less than that of the series/parallel double RC model and higher than that of constant RC model. However, the constant RC model is inaccurate, especially in high frequency regime. In addition, the proposed technique can be easily incorporated into computer aided circuit design software, such as SPICE and ADS software, to simulate circuits containing RTD in high frequency regime. In brief, this work adds important contributions to the accurate characterization and modeling of RTDs and analyzes its based circuits in high frequency regime by addressing the problems of the current RTD equivalent circuit models. [ABSTRACT FROM AUTHOR]

In negative capacitance field-effect transistors (NCFETs), drain current may decrease with increasing ${V}_{\mathrm {ds}}$ in the saturation region, leading to negative differential resistance (NDR). While NDR is useful for oscillator design, it is undesirable for most analog circuits. On the other hand, the tendency toward NDR may be used to reduce the normally positive output conductance ( ${g}_{ \mathrm {ds}}$ ) of a short-channel transistor to a nearly zero positive value to achieve higher voltage gain. In this paper, we analyze the NDR effect for NCFET in the static limit and demonstrate that it can be engineered to reduce ${g}_{\mathrm {ds}}$ degradation in short-channel devices. Small and positive $g_{\mathrm{ ds}}$ is achieved without compromising the subthreshold gain, which is crucial for analog applications. The 7-nm ITRS 2.0 FinFET with 0.7 V ${V}_{\mathrm {dd}}$ is used as the baseline device in this paper. [ABSTRACT FROM AUTHOR]

Achieving sub-60 mV/decade subthreshold swing in short channel Negative Capacitance Field Effect Transistor (NCFET) devices requires the utilization of a thicker Ferroelectric (FE) layer, where due to an interplay between the thickness and polarization gradient of the FE material, undesired effects such as Hysteresis and Negative Differential Resistance (NDR) may be seen in the device characteristics, which limits the expected improvement in the performance. In this work, with a Fully Depleted Silicon-on-insulator (FDSOI) baseline architecture, at a channel length of 14 nm, through utilizing a drain-sided Paraelectric (PE) spacer along with reduced drain doping while laterally splitting the gate stack into two halves such that the nature of the material on the source-sided and drain-sided stack is Ferroelectric and Paraelectric respectively, we show an NDR-free output characteristic. This also enables the incorporation of a thicker FE layer, without observing Hysteresis in the transfer characteristics, while ensuring significantly high Gain ( g m / g d s ) along with sub-60 mV/decade subthreshold swing, at lower supply voltages. [ABSTRACT FROM AUTHOR]

A negative differential resistance fin-shaped field-effect transistor (NDR-FinFET) using a Pb(Zr0.52Ti0.48)O3 threshold selector (TS) is investigated. From the measured input transfer characteristic of NDR-FinFET, the following results are demonstrated: 1) superior reduction of off current by a factor of 350 (as compared to a baseline FinFET); 2) on current of NDR-FinFET comparable to that of the baseline FinFET; and 3) subthreshold slope of 3 mV/decade at 300 K. The operating principle of NDR-FinFET is demonstrated using MATLAB simulation. In the on-to-off and off-to-on switching processes, the existence of an unstable resistive switching region is verified through the comparison between simulation data and experimental results. The major device parameters that affect the formation of the unstable resistive switching region are revealed. Finally, it is proposed that: 1) lowering the hold voltage of the TS and 2) applying the drain voltage comparable to the threshold voltage can have the NDR-FinFET to work appropriately (i.e., not in unstable region). [ABSTRACT FROM AUTHOR]