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Abstract As a superior p-type wide bandgap semiconductor, β-CuSCN has a huge potential in optoelectronic device application, and however its conduction could intensively be affected by externally applied bias. Here, we demonstrate electrodeposited individual β-CuSCN trigonal micro/nanopyramids and their array films can show Cu+ trap-controlled bias dependence of electron transport. Before being subjected to a large reverse bias or a unidirectional bias, their cyclic I V curves are coincident resulted from bulk-trap related carrier hopping. At relatively large bidirectional operation bias, they can symmetrically present two large hysteresis loops with negative differential resistance (NDR), and meanwhile accompany with nonvolatile negative resistive switching (RS) feature. After being applied respectively a relatively large fixed bias in two opposite directions, more importantly, switchable classic asymmetrical bipolar RS can successfully be realized at a relatively low operation bias. The switchable formation of reversion and depletion layer, resulted from the minority carriers (electrons) injection into the traps of surface connected with negative electrode, plays a crucial role. Under relatively large bias, the synergistic effect of two surface trap-related back-to-back connected bipolar RS devices results in symmetrical negative RS with NDR. After being applied a relatively large fixed bias, the bipolar RS effect can be enhanced at the surface connected with negative electrode due to the presence of electron injection induced high and narrow barrier, and conversely it disappears at the surface connected with positive electrode due to hole injection-induced ohmic contact. Then, the devices can be set and reset by the filling and emptying of holes in the thin reversion and depletion layer at low reverse and forward voltages, respectively, showing switchable bipolar RS behavior. Due to superior stability, reversibility, nondestructive readout, and low operation bias as well as remarkable cycle performance, the bias-governed conduction with negative RS and switchable bipolar RS makes it a potential candidate in next-generation erasable nonvolatile RRAM devices. Graphical abstract Individual β-CuSCN trigonal micro/nanopyramids and their array films can show Cu+ trap-controlled bias dependence of conduction. Before, under and after applying a large bias, they can show the behaviour of bulk-trap related carrier hopping, symmetrical nonvolatile negative RS characteristics with NDR, and switchable bipolar RS, respectively. The switchable formation of electron injection-induced reversion and depletion layer plays a crucial role at the surface connected with negative electrode. Unlabelled Image Highlights • Individual β-CuSCN micro/nanopyramids and their array films can show bias dependence of electron transport characteristics. • Before being subjected to a large reverse bias or at a unidirectional bias, their cyclic I-V curves are coincident. • Two symmetrical hysteresis loops with negative differential resistance only appear at large bidirectional operation bias. • Switchable bipolar resistive switching is realized after applying large fixed bias in two opposite directions, respectively. • Negative resistive switching can controllably be set and reset by large reverse and forward bias voltage, respectively. [ABSTRACT FROM AUTHOR]

By combining non-equilibrium Green's function (NEGF) with density functional theory (DFT), we systematically study the spin-related transport properties of the heterostructures composed of graphene and hexagonal boron-nitride (h -BN) when the metal Fe is doped different positions of the heterostructures interface. The results show that the heterostructures exhibit obvious spin-filtering effect (SFE) and negative differential resistance (NDR) due to the different absorbing positions of the metal Fe. And the spin filtering ratio can reach more than 90% in a specific bias voltage range. Moreover, spin-rectifying behaviors are detected in the heterostructures. Whether it is for the design of multifunctional devices or the synthesis of spintronic devices, these findings will have some reference value. • We study the spin transport properties of the Fe-doped graphene/ h -BN heterostructures. • Geometric optimizations and spin transport properties are calculated by combining the NEGF with DFT. • Spin-filtering effect, negative differential resistance and spin-rectifying are found in the devices. • It can be widely used in future multifunctional nanoelectronic devices. [ABSTRACT FROM AUTHOR]

Using density functional theory combined with non-equilibrium Green's function method, we investigate the spin-dependent transport properties of debrominated tetrabromopolyaromatic (D-TBPA) molecules embedded between zigzag graphene nanoribbon electrodes, and the effects of copper and cobalt side doping have also been considered. Our results show that the copper doping can insert new energy levels around the Fermi Level and keep spin degeneration of band structure, the cobalt doping can also induce spin splitting. The results on spin transport properties of D-TBPAs embedded into zigzag graphene nanoribbon electrodes show that these systems exist spin filtering and negative differential resistance behaviors. Corresponding physical mechanism on the spin-dependent transport property has been revealed according to the frontier molecular orbital characteristics. • The spin-dependent transport properties of debrominated tetrabromopolyaromatic (D-TBPA)-ZGNRs molecular devices. • The effects of copper and cobalt atoms side doping. • The spin filtering effect and negative differential resistance behaviors can be observed. [ABSTRACT FROM AUTHOR]

Light emitting diodes based on gallium arsenide-phosphide solid solutions were studied. Negative differential resistance regions were identified at lower temperatures T ≤ 130 K. Irradiation of diodes by electrons (E = 2 MeV) leads to the increase in the differential resistance, change in the contact potential difference, and a drop in the radiation intensity. These effects are due to the influence of deep radiation defects levels and surface states, activated by high levels of the ionization excitation peculiar to electron irradiation. [ABSTRACT FROM AUTHOR]

A double-stranded DNA molecule subject to a perpendicular gating electric field and a small mechanical strain exhibits a negative differential resistance (NDR) in its current–voltage (I–V) characteristics. Using an advanced two-dimensional tight-binding model including hopping integrals for the next nearest-neighbors, we implement perturbative strain- and tilted angle-dependent DNA helix conformation in conjunction with the theories of Slater–Koster and linear elasticity. The degree of NDR can be tuned by adjusting the tilt angle and mechanical strain of the DNA. This effect arises because of a surface charge distribution near the contacts due to the normal component of the electric field and structural change of the DNA molecule due to the strain. It is shown that enhancement of NDR peak current and a large peak-to-valley ratio of NDR are achieved by an increase of the tilt angle and stretching strain. Finally, a series of step-like current jumps without NDR features are exhibited in the weak DNA-lead coupling regime. This disappearance of NDR stems from the fact that reduced conduction through metal electrodes with a sufficiently small tunneling rate compensates the current drop. [ABSTRACT FROM AUTHOR]

Highlights • The Fe doped SnS 2 system exhibits multiple spin-resolved transport properties of negative differential resistance and large TMR. • Near 100% spin polarization was realized in the parallel spin configuration. • 104 magnitude of TMR has been realized under a wide bias window. • The spin down d states of Fe near E F is the essential reason of the NDR behavior and large TMR. Abstract In this work, the spin-resolved transport properties of the Fe doped SnS 2 monolayer devices have been investigated. The results show that the doping systems have the transport properties of negative differential resistance, large magnetoresistance effect and near 100% spin polarization effect when the magnetization directions of two electrodes are in parallel. Moreover, the mechanisms for the properties also have been discussed. The original reason of these results could be due to the half-metallic of the doping system. Our results imply that Fe doped SnS 2 monolayer is a promising candidate for the future spintronic devices. [ABSTRACT FROM AUTHOR]

Highlights • The spin transport properties of zigzag C 2 NNR/GNR hybrid device. • Edge hydrogenation and oxidation effects to the device performance is revealed. • Perfect spin-filtering and strong NDR effects are obtained by edge oxidation. Abstract Based on density functional theory and non-equilibrium Green's function, we investigate the edge hydrogenation and oxidation effects on the spin transport of devices consisting of a zigzag C 2 N nanoribbon (ZC 2 NNR) embedded in zigzag graphene nanoribbons in parallel (P) and antiparallel (AP) spin configurations. The results show that device with edge hydrogenation exhibits dual spin filtering effect in AP spin configuration and obvious negative differential resistance in both P and AP spin configuration. By substituting oxygen for hydrogen as passivation atoms of ZC 2 NNR, the spin filtering efficiency is as high as 100% in the P spin configuration, and the negative differential resistance is largely enhanced with a peak to valley ratio in excess of 4×103. Our theoretical studies suggest that zigzag C 2 N nanoribbon modulated by edge substitution has great potential in the design of future multifunctional spin devices. [ABSTRACT FROM AUTHOR]

Abstract This study demonstrates quantum-dot light-emitting diodes (QD-LEDs) with a function of resistive switching memory, capable of on/off operation at the same driving current depending on reset/set state. The QD-LEDs were fabricated by spin-coating process and experienced two different annealing conditions, which yielded defective or less-defective V 2 O 5– x layer. One of the annealing conditions produced QD-LEDs with the unusual electrical behaviors of negative differential resistance (NDR), capacitance oscillation, and voltage–current hysteresis curves, signifying so-called resistive switching characteristics. X-ray and ultraviolet photoelectron spectroscopies were used to examine the chemical state of the differently annealed V 2 O 5– x layers. The less stoichiometric V 2 O 5– x layer was found to be responsible for the resistive switching behaviors of the NDR and the low and high resistance states (LRS and HRS, respectively). We discuss the LRS/HRS of V 2 O 5– x for resistive switching in terms of a conductive filament effect, induced by microstructural changes caused by oxygen drift and vacancy annihilation processes in the high defect density V 2 O 5– x layer. Graphical abstract Image 1 Highlights • Quantum-dot light-emitting diode (QD-LED) with resistive switching function is demonstrated. • Defective V 2 O 5 layer is responsible for the resistive switching behavior inside the QD-LED. • The resistive switching function is discussed in terms of microstructural changes based on conductive filament effect. • We further demonstrate the on/off operation of QD-LEDs at the same driving current depending on reset/set state. [ABSTRACT FROM AUTHOR]

The band gap of armchair graphene nanoribbons (AGNRs) can be modulated by replacing the carbon atoms with boron/nitride (BN) atoms to produce the compound nanoribbons, while the width of ribbons remains constant. By introducing BN doping atoms in the proper positions along the ribbon length, a double-barrier quantum-well structure is constructed. Consequently, negative differential resistance properties can be obtained by a combination of armchair BN nanoribbons (ABNNRs) and AGNRs as the compound ABNxGyNRs, in which x and y denote the number of BN and C atoms in the ribbon width, respectively. The proposed resonant tunneling diode (RTD), called an armchair BN graphene nanoribbon resonant tunneling diode (ABNGNR-RTD), is investigated in three different platforms including W, S, and H shapes. The numerical tight-binding model along with non-equilibrium Green's function formalism is taken into account to study the electronic properties of the proposed RTD. The performance of the ABNGNR-RTD is examined in terms of device characteristics such as peak-to-valley ratio (PVR) and power dissipation. Based on the presented results, the performance of H-shaped devices is better than those of the other two cases in terms of PVR and power dissipation. In addition, the electronic properties of ABNGNR-RTDs can be modified by varying the relative width of ABNNRs with respect to AGNRs. [ABSTRACT FROM AUTHOR]

By employing spin‐polarized density functional theory (DFT) combined with non‐equilibrium Green's function technique (NEGF), we have investigated the spin transport properties of a series of manganese diporphyrins (MnDPs) with different torsion angle (θ=0°, 10°, 20°, 30°, 40°, 50°, 60°). It is found that the spin transport properties of molecular junctions can be modulated by mechanical tuning of different dihedral angle. In addition, the molecular junctions have characterized Giant magnetoresistance (GMR), spin filtering effect (SFE) and negative differential resistance (NDR). More interestingly, our results show that the MR could reach over 14000 % at low bias voltage, and nearly perfect spin filtering efficiency can be obtained when the torsion angle θ=20°. The numerical analysis reveals that the matching of PDOS for two parts of MnDP molecule is the physical mechanism which is causing the appearance of GMR in the low bias voltage. Our findings might be useful for the application of MnDP‐based molecular devices. Molecular electronics: the ability to manipulate electron spin in organic molecular materials offers a new and tantalizing route towards spin electronics. The spin transport properties of molecular junctions can be modulated by mechanical tuning of different dihedral angles. A giant magnetoresistance (over 14000 %) is found under low bias voltage and that can be engineered by an appropriate choice of different dihedral angles. [ABSTRACT FROM AUTHOR]

Porous organic/inorganic nanocomposites were synthesized by sol-gel technique after the incorporation of nickel oxide (NiO) nanoparticles in carbon composite based on pyrogallol and formaldehyde (PF) using picric acid as catalyst. After a drying step, the samples were heated during 2 h at different pyrolysis temperatures from 600 to 1000 °C in tubular furnace under nitrogen atmosphere. The XRD pattern exhibit that PF composite is amorphous even after thermal treatment at 1000 °C. On the other hand, the PF/NiO nanocomposites are crystallized with the appearance of the graphite structure at high pyrolysis temperature. The gas adsorption capacities for CO2 indicate that the PF composite has a tendency to adsorb CO2 higher than PF/NiO nanocomposite. In fact, the maximum value of capacity is of the order 7.5 mmol/g in PF composite and 6.5 mmol/g in PF/NiO nanocomposite. The dc conductivity shows the dominance of percolation phenomenon and explained by two models; the three dimensions variable range hopping and the nearest neighbor hopping. The voltage-current V(I) characteristics show the presence of negative differential resistance at room measurement temperature in PF/NiO-625 °C sample. The ac conductance is attributed to different origins, so it is decried by two models, like hopping conduction mechanism in PF-675 °C composite and small polaron hopping model in PF/NiO-625 °C nanocomposite. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract The electronic structures of the C and O-doped black phosphorene are investigated theoretically by using first-principles density functional theory (DFT). The results show that they are all metallic. And the black phosphorus nanotubes (BPNTs) rolled from the pure, C-doped and O-doped black phosphorene with different radii and chiralities are also studied. C and O atoms substitute for P atoms enable the armchair BPNT to have a metallic feature with several bands cross the Fermi level. Surprisingly, the number of the bands cross the Fermi level just equals the number of dopant atoms. But for the zigzag BPNT, when the O atoms decrease to 4, no band crosses the Fermi level and at which a minimal energy gap appears. Furthermore, the transport properties of two-probe devices fabricated by the pure A24 and Z34 BPNTs together with the C-doped A24 BPNTs are investigated theoretically. These calculated results show that the electronic transport properties of the A24 BPNT can be significant changed by C dopant atom and vary with the number of the doped atoms. The current-voltage curves of these BPNTs with C atoms substitute for P atoms present sinusoidal characteristics under low bias and negative differential resistance (NDR) properties. This study provides an effective route for tuning the electronic structures of black phosphorene and BPNTs and thus the transport properties of their electronic devices. And the unique properties of these black phosphorene and BPNTs also offer an inspiration for their subsequent experiments. [ABSTRACT FROM AUTHOR]

We fused zigzag graphene to boron nitride nanoribbons by gradually doping C atoms at only one edge of the ribbons to design a hybridized ZBxNyCz (x + y + z = 12) structure. To create asymmetric edge hydrogenation, the ZBxNyCz ribbons were monohydrogenated (N-H) at one edge and dihydrogenated (C-H2) at the opposite edge, and the structure was subsequently labeled as H-ZBxNyCz-H2. On the basis of density functional theory and non-equilibrium Green's function, our simulation revealed that H-ZBxNyCz-H2-based devices present a variety of abnormal spin-polarized transport properties. When the value of x and y in the H-ZBxNyCz-H2 structure is not equal (i.e., z is an odd number), the spin-polarized currents are restricted, regardless of their ferromagnetic (FM) or anti-ferromagnetic (AFM) state. When x is equal to y (i.e., z is an even number), the H-ZBxNyCz-H2 structure exhibits negative differential resistance and spin-filtering features in the FM state. Conversely, in the AFM state, the spin-polarized currents of the structure exhibit an exceptional oscillation effect with spin polarization as high as 100% at certain bias voltages. By adjusting the width of graphene and the spin states, the resulting hybridized H-ZBxNyCz-H2 structure can be potentially applied to the fabrication of spin nanodevices with exotic functionalities. [ABSTRACT FROM AUTHOR]

Resistive switching (RS) phenomenon at a power level on the order of nW is observed in a porous α-Fe 2 O 3 thin film. The samples are prepared on glass substrates using spin coating with a sol-gel solution of 141.5 mM Fe(III) acetylacetonate in acetone followed by annealing at 550 °C for 75 min in air. This process produces a semi-continuous α-Fe 2 O 3 thin film. AC I-V curves were acquired in a humidity-controlled environment, where otherwise the I-V characteristics are linear. Sweeping the voltage of the device from 0 to 10 V at the rate of 0.2 V/s with a triangular waveform, the device is in a low resistive state (LRS) from 0 to ∼4 V, at which point the current sharply decreases from ∼4–10 V, which is the signature of a negative differential resistance (NDR). Sweeping back from 10 to 0 V, the device remains in a high resistive state (HRS). The I-V curves are symmetric and highly reproducible, exhibiting the RS and NDR phenomena in the negative bias. A ratio of HRS/LRS > 12 at 2 V bias was achieved in both positive and negative bias regions. The RS and symmetric NDR behavior of the device is attributed to the trapping and de-trapping of the carriers at the space charge region formed by the movement of ions from water molecule dissociation towards respective electrode/material interface. [Display omitted] • The co-existence of resistive switching (RS) and negative differential resistance is an interesting phenomena and shown to exist in number of literatures with poor reproducibility because of their accidental occurrence or poor stability at room temperature. We believe this work will be impactful because of its application to humidity sensing, but also as a sensor for use in neuromorphic computing because of the memristive nature of the device. • When a repetitive triangular form of voltage sweeps are done in humid environment, the current voltage curve is shown to have RS and NDR behavior with excellent reproducibility. We extracted the High and Low resistive states (HRS and LRS) at specific bias voltage and proposed to use their ratio as a parameter to quantify the relative humidity of an unknown environment. • The careful fitting of the I-V curve with a function formed with the combination of different transport mechanisms suggests that the space charge limited current is responsible for the co-existence of RS and NDR in α-Fe 2 O 3 porous thin film device. [ABSTRACT FROM AUTHOR]

The memory storage and processing capability of human brain is throwing excitement and challenges to create a low power consuming "brain-like functioning device" called neuromorphic device which is the basis of automation and robotics. We demonstrate a robust and highly efficient two-terminal device (Al/Indigo/Al) based on natural indigo molecules to emulate synaptic functionalities for use in neuromorphic applications. The indigo molecules are sourced from plants and are stable at room temperature. Molecules exhibit an optical energy gap of ∼ 1.9 eV evidenced by UV–vis spectroscopy. A detailed analysis of conduction mechanism is performed via dc-electrical characteristics. Consistent negative differential resistance (NDR) is observed, which we attribute to the deep trap states. The analysis shows that conduction is due to the trap-assisted Poole-Frenkel effec. The device maintains an extremely stable high-resistance state (HRS) and low resistance state (LRS) up to 9000 cycles of read – write - erase operation. Further, the essential characteristics such as paired pulse facilitation (PPF) and paired pulse depression (PPD) have been measured on the device. Potentiation (learning) and depression (forgetting) curves follow double exponential with more than 85% of the potentiation/depression occurring in the initial few pulses. Non-linearity (NL) calculations suggest that the device performance can be tuned by carefully choosing the pulse voltage and pulse width such that the nonlinearity factor is reduced. This work clearly indicates an easy approach for the fabrication of natural organic molecule-based artificial synapse that works efficiently at room temperature, as well as the method for selecting measurement parameters to obtain low-power consuming artificial synapse. [Display omitted] • Naturally occurring indigo molecular film is used for fabricating a two-terminal electronic device (Al/Indigo/Al) exhibiting resistive switching. • Extremely consistent negative differential resistance (NDR) is observed in the devices. Trap-assisted Poole-Frenkel effect is found to dominate the conduction within the NDR region. • The device shows synaptic characteristics such as potentiation (learning) and depression (forgetting). The measurements show extremely stable potentiation (learning) and depression (forgetting) for more than 10 cycles. • The measurements and calculations indicate that the performance of the molecular device could be fine tuned to achieve a lesser non-linearity in the learning and forgetting function, which is one of the most desirable factors for developing a superior artificial synapse. • Neuromorphic performance of the device can be modifued by choosing appropriate pulse voltage to fine tune the nonlinearity in the learning and forgetting process [ABSTRACT FROM AUTHOR]

We conducted a theoretical scrutiny on the quantum spin transport characteristics of a class of open-shell 3d-transition metal (TM = Mn, Fe, Co, and Ni) (II) phthalocyanines (TMPcs) molecules sandwiched between two semi-infinite armchair single-walled carbon nanotube probes. Herein, the spin density functional formalism is utilized in conjunction with state-of-the-art non-equilibrium Green's function technique. Molecular junctions composed of MnPc and FePc have higher local magnetic spin moments than CoPc and NiPc because of the strong exchange spin-splitting between the 3d-states of the Mn or Fe cation atoms and the p-states of the N anion atom. This indicates that TMPc molecules (TM = Mn, and Fe) bridged between two single-walled carbon nanotube (SWCNT) electrodes with a π-type geometry demonstrate a pronounced transmission near the Fermi level. Furthermore, the sign and robustness of spin filter efficiency are tailored by manipulating the central atom of 3d-transition metal and the contact SWCNT electrodes. Subsequently, FePc and MnPc molecular junctions have the advantage of operating practically as ideal spin filter devices compared to CoPc and NiPc molecular structures. Moreover, the tunneling magnetoresistance (TMR) of these molecular devices is assessed. For MnPc and FePc molecular junctions, the estimated total conductance exhibited a robust trend at zero bias voltage, whereas the magnitudes of spin-up and spin-dn quantum conductances increased significantly in CoPc and NiPc molecular configurations with bias voltages range between ±0.45 and ±0.95 Volt. Spin-down carriers essentially govern the quantum conductance of TMPc (Mn, Fe, Co, and Ni) molecular junctions at bias voltage around ±0.75 Volt. By examining their I-V characteristics, it has been established that MnPc, and FePc molecular junctions exhibit metal-like behavior, whereas CoPc and NiPc molecular devices are subject to negative differential resistance. As a result of our theoretical findings, it is found that TMPcs (TM = Fe, Mn) coupled to SWCNT probes yield a robust spin filter efficiency that may be of interest for prospective technological realizations in organic-inorganic molecular spintronic devices. [Display omitted] • Spin transport features of 3d-TMPcs (TM = Mn, Fe, Co, and Ni) molecules coupled to two CNT probes were analyzed. • FePc and MnPc molecular devices revealed a significant transmission near the Fermi level. • At zero bias voltage, the total conductances of MnPc and FePc molecular junctions were found to be strong. • The I-V characteristics of CoPc, and NiPc molecules exhibited an NDR behavior. • FePc and MnPc coupled to the CNT leads indicated a robust spin filter efficiency useful in molecular spintronic devices. [ABSTRACT FROM AUTHOR]

• We systematically investigated the impact of ferroelectric (FE) layer thickness (t FE) on the electrical parameters of a Negative Capacitance QuadFinFET (NC-QuadFinFET) using 3D TCAD simulator. • The Increase in t FE leads to higher I ON / I OFF current ratio but also enhances hysteresis. However, it is also witnessed that at a certain ferroelectric layer thickness, the NC-QuadFinFET suffers from negative DIBL owing to Negative Differential Resistance (NDR). • Although NDR is beneficial for oscillator designs, it is undesirable for most analog circuits. Hence, keeping the same gate length and t FE fixed, the NC-quadFinFET is further optimized using alternative techniques to reduce the NDR effects. • By extending the drain length and with the implementation of Si 3 N 4 Spacer, an enhancement in the electrical parameters as well as the intrinsic gain of the device is exhibited. • The NC Quad-FinFET with drain engineered and Si3N4 spacer implementation as a digital inverter shows a considerable 27.65% decrement in the circuit propagation delay. As a result, the optimized NC-quadFinFET is a potential candidate for ultralow-power applications and analog circuits. In this work, a systematically analysis of the Negative Capacitance (NC) Quad-FinFET structure is carried out where we determine the optimal FE layer thickness that enables hysteresis-free transfer characteristics. However, negative differential resistance (NDR) is introduced along with the increased FE-layer thickness, which is not desirable for application in analog circuits. Through the implementation of an asymmetric drain length extension and a high-k Si 3 N 4 spacer, negative differential resistance (NDR) can be mitigated. In addition, the relatively poor analog performance generally seen in conventional FinFET structures are overcome in the drain engineered NC Quad-FinFET structure with gate spacer resulting in significant improvement in performance parameters such as transconductance, output conductance and intrinsic gain. The integration of NC Quad-FinFET as a digital inverter is carried out where the circuit propagation delay is decreased by 27.65% with drain length extension and inclusion of Si 3 N 4 spacer. Thus, through these device optimization techniques, the NC Quad-FinFET structure shows significant improvement in both analog and digital device performance parameters. [ABSTRACT FROM AUTHOR]

As a sanity test for the theoretical method employed, studies on (steady-state) charge transport through molecular devices usually confine themselves to check whether the method in question satisfies the charge conservation. Another important test of the theory’s correctness is to check that the computed current does not depend on the choice of the central region (also referred to as the “extended molecule”). This work addresses this issue and demonstrates that the relevant transport and transport-related properties are indeed invariant upon changing the size of the extended molecule, when the embedded molecule can be described within a general single-particle picture (namely, a second-quantized Hamiltonian bilinear in the creation and annihilation operators). It is also demonstrates that the invariance of nonequilibrium properties is exhibited by the exact results but not by those computed approximately within ubiquitous wide- and flat-band limits (WBL and FBL, respectively). To exemplify the limitations of the latter, the phenomenon of negative differential resistance (NDR) is considered. It is shown that the exactly computed current may exhibit a substantial NDR, while the NDR effect is absent or drastically suppressed within the WBL and FBL approximations. The analysis done in conjunction with the WBLs and FBLs reveals why general studies on nonequilibrium properties require a more elaborate theoretical than studies on linear response properties (e.g., ohmic conductance and thermopower) at zero temperature. Furthermore, examples are presented that demonstrate that treating parts of electrodes adjacent to the embedded molecule and the remaining semi-infinite electrodes at different levels of theory (which is exactly what most NEGF-DFT approaches do) is a procedure that yields spurious structures in nonlinear ranges of current–voltage curves.

This paper proposes a new class of resonant tunneling diodes (RTDs) that are planar and realizable with a single graphene nanoribbon. Unlike conventional RTDs, which incorporate vertical quantum well regions, the proposed devices incorporate two confined planar quantum dots within the single graphene nanoribbon, giving rise to a pronounced negative differential resistance (NDR) effect. The proposed devices, termed here as planar double-quantum-dot RTDs, and their transport properties are investigated using quantum simulations based on nonequilibrium Green's function formalism and the extended Huckel method. The proposed devices exhibit a unique current-voltage waveform consisting of a single pronounced current peak with an extremely high, in the order of 104, peak-to-valley ratio. The position of the current peak can be tuned between discrete voltage levels, allowing digitized tunability, which is exploited to realize multi-peak NDR devices.

Memristive systems can provide a novel strategy to conquer the von Neumann bottleneck by evaluating information where data are located in situ. To meet the rising of artificial neural network (ANN) demand, the implementation of memristor arrays capable of performing matrix multiplication requires highly reproducible devices with low variability and high reliability. Hence, we present an Ag/CuO/SiO2/p-Si heterostructure device that exhibits both resistive switching (RS) and negative differential resistance (NDR). The memristor device was fabricated on p-Si and Indium Tin Oxide (ITO) substrates via cost-effective ultra-spray pyrolysis (USP) method. The quality of CuO nanoparticles was recognized by studying Raman spectroscopy. The topology information was obtained by scanning electron microscopy. The resistive switching and negative differential resistance were measured from current–voltage characteristics. The results were then compared with the Ag/CuO/ITO device to understand the role of native oxide. The interface barrier and traps associated with the defects in the native silicon oxide limited the current in the negative cycle. The barrier confined the filament rupture and reduced the reset variability. Reset was primarily influenced by the filament rupture and detrapping in the native oxide that facilitated smooth reset and NDR in the device. The resistive switching originated from traps in the localized states of amorphous CuO. The set process was mainly dominated by the trap-controlled space-charge-limited; this led to a transition into a Poole–Frenkel conduction. This research opens up new possibilities to improve the switching parameters and promote the application of RS along with NDR.

Electroluminescence of green N-doped gallium phosphide light-emitting diodes was studied. The negative differential resistance region in the current-voltage characteristics was found at low temperature (Т ≤ 90 К). Possible reason of this phenomenon is the redistribution of recombinational flows between annihilation channels on isolated nitrogen atoms and annihilation channel on the NN1 pairs.

Graphical abstract Abstract Chemical decorated heterojunction Pb/Pb-Si nanochain devices and their electron transport properties are systematically investigated. These Pb-Si nanochain heterostructures are found to show semimetal and graphene-like properties on electronic transport. Particularly, some devices show some excellent performance with large on-off ratios, small sub-threshold swing and high peak-to-valley ratio (PVR). A link between heterojunction mode and semiconductor-semimetal-metal transformation characteristic has been built. In addition, multi-peak negative differential resistance (NDR) effect has been observed on this heterostructure. Moreover, the performance of heterojunction Pb/Pb-Si nanochain devices is observed to be effectively modulated by gate potential. These findings are very valuable for potential implications for the design of high-performance new-generation microelectronic devices. [ABSTRACT FROM AUTHOR]

We report large amplitude modulation waveforms as large as ~ 10 V using vanadium dioxide micro-channel devices operating under current-controlled conditions. The self-sustained electrical oscillations were generated by controlling the applied current in the negative differential resistance region of the investigated devices. An appropriate value of internal capacitance was achieved as parasitic capacitance in the device structure to stabilize the electrical oscillations. This eliminates the need of an external pulsed source or any external passive component connected to the micro-channel devices. Amplitude and frequency of the oscillation were tuned by illuminating the device micro-channel with an external laser. An equivalent circuit model was developed to simulate the waveforms. A good agreement between experiment and simulation was verified. [ABSTRACT FROM AUTHOR]

Bottom-up synthesis of graphene nanoribbons (GNRs) by surface-assisted polymerization and cyclodehydrogenation of specifically designed precursor monomers has been shown to yield precise edges and doping. Here we use a precursor monomer containing sulfur atoms to fabricate nanostructures on a Au(111) surface at different annealing temperatures. The nanostructures have distinct configurations, varying from sulfur-doped polymers to sulfur-doped chevron-type GNRs (CGNRs) and, finally, pristine graphene nanoribbons with specific edges of periodic five-member carbon rings. Non-contact atomic force microscopy provides clear evidence for the cleavage of C-S bonds and formation of pristine CGNRs at elevated annealing temperatures. First-principles calculations show that the CGNRs exhibit negative differential resistance. [ABSTRACT FROM AUTHOR]

The electronic transport properties of oligo p-phenylenevinylene (OPV) molecule sandwiched with symmetrical or asymmetric tailoring graphene nanoribbons (GNRs) electrodes are investigated by nonequilibrium Green's function in combination with density functional theory. The results show that different tailored GNRs electrodes can modulate the current–voltage characteristic of molecular devices. The rectifying behavior can be observed with respect to electrodes, and the maximum rectification ratio can reach to 14.2 in the asymmetric AC–ZZ GNRs and ZZ–AC–ZZ GNRs electrodes system. In addition, the obvious negative differential resistance can be observed in the symmetrical AC-ZZ GNRs system. [ABSTRACT FROM AUTHOR]