The effects of spin-filter and negative differential resistance on Fe-substituted zigzag graphene nanoribbons

Using the first-principle calculations, we investigate the spin-dependent transport properties of Fe-substituted zigzag graphene nanoribbons (ZGNRs). The substituted ZGNRs with single or double Fe atoms, distributing symmetrically or asymmetrically on both edges, are considered. Our results show Fe-substitution can significantly change electronic transport of ZGNRs, and the spin-filter effect and negative differential resistance (NDR) can be observed. We propose that the distribution of the electronic spin-states of ZGNRs can be modulated by the substituted Fe and results in the spin-polarization, and meanwhile the change of the delocalization of the frontier molecular orbitals at different bias may be responsible for the NDR behavior.     

Low bias negative differential resistance with dual-peaks based on octacene molecular device

Based on non-equilibrium Green's function and density functional theory, a first-principles study of the transport properties of a molecular device is performed. This device is composed of two octacene molecules separated by a ethyl barrier, which are then linked to Ag leads through thiolates. The device shows low bias negative differential resistance effect with dual-peaks, which may be useful for designing molecular devices with low power-dissipation and multi-function in the future.     

Pseudomorphic InGaAs quantum-wire FETs with negative differential resistance

Pseudomorphic trench-type InGaAs/InAlAs quantum-wire field-effect transistors (QWR-FET) are realized by selective molecular beam epitaxy. The pseudomorphic QWR-FET has a negative differential resistance (NDR) effect with a low source–drain voltage (0.3 V). The NDR spectra are clearly observed in the 50–220 K temperature range. The operating current of the pseudomorphic QWR-FET is twice that of a lattice-matched QWR-FET, and this is thought to be due to the higher electron mobility.     

Tuning spin-filtering,rectifying, and negative differential resistance by hydrogenation on topological edge defects of zigzag silicene nanoribbons

By first-principles calculations, we propose three heterojunction nanodevices based on zigzag silicene nanoribbons with different edge-hydrogenated topological line defects. The devices all present excellent spin-filtering properties with 100% spin polarization as well as remarkable rectifying effect (with rectification ratio around 10²) and negative differential resistance behaviors. Our findings shed new light on the design of silicon-based nanodevices with intriguing spintronic applications.     

Modulation of rectification and negative differential resistance in graphene nanoribbon by nitrogen doping

By applying the nonequilibrium Green?s function formalism combined with density functional theory, we have investigated the electronic transport properties of two nitrogen-doped armchair graphene nanoribbon-based junctions M1 and M2. In the left part of M1 and M2, nitrogen atoms are doped at two edges of the nanoribbon. In the right part, nitrogen atoms are doped at one edge and at the center for M1 and M2, respectively. Obvious rectifying and negative differential resistance behaviors are found, which are strongly dependent on the doping position. The maximum rectification and peak-to-valley ratios are up to the order of 10⁴ in M2.     

Carbon doping induced giant low bias negative differential resistance in boron nitride nanoribbon

By applying nonequilibrium Green's function combined with density functional theory, we investigated the electronic transport properties of carbon-doped armchair boron nitride nanoribbons. Obvious negative differential resistance (NDR) behavior with giant peak-to-valley ratio up to the order of ${10}^4\text{–}{10}^6$ is found by tuning the doping position and concentration. Especially, with the reduction of doping concentration, NDR peak position can enter into mV bias range and even can be expected lower than mV bias. The negative differential resistance behavior is explained by the evolution of the transmission spectra and band structures with applied bias.     

Spin-dependent transport properties of debrominated tetrabromopolyaromatic with Cu or Co doping embedded between zigzag graphene nanoribbon electrodes

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.     

Physical mechanism of negative differential conductance in substrateless metallic carbon nanotubes

The existence of pronounced negative differential conductance at room temperature in suspended metallic carbon nanotubes was recently proven. We investigate here the physical nature of this phenomenon, which is of considerable importance for high-frequency devices, such as oscillators working up to few hundreds of GHz. Besides previous explanations, we find a new physical mechanism that explains the negative differential conductivity at room temperature. The entire suspended metallic carbon nanotube behaves as a very large quantum well, the negative differential conductance occurring due to the depletion of carriers on high-energy resonant levels.     

Large negative differential resistance in graphene nanoribbon superlattices

A graphene nanoribbon superlattice with a large negative differential resistance (NDR) is proposed. Our results show that the peak-to-valley ratio (PVR) of the graphene superlattices can reach 21 at room temperature with bias voltages between 90–220 mV, which is quite large compared with the one of traditional graphene-based devices. It is found that the NDR is strongly influenced by the thicknesses of the potential barrier. Therefore, the NDR effect can be optimized by designing a proper barrier thickness. The large NDR effect can be attributed to the splitting of the gap in transmission spectrum (segment of Wannier–Stark ladder) with larger thicknesses of barrier when the applied voltage increases.     

Large negative differential resistance behavior in arsenene nanoribbons induced by vacant defects

We have studied the electronic structures of arsenene nanoribbons with different edge passivations by employing first-principle calculations. Furthermore, the effects of the defect in different positions on the transport properties of arsenene nanoribbons are also investigated. We find that the band structures of arsenene nanoribbons are sensitive to the edge passivation. The current-voltage characteristics of unpassivated and O-passivated zigzag arsenene nanoribbons exhibit a negative differential resistance behavior, while such a peculiar phenomenon has not emerged in the unpassivated and O-passivated armchair arsenene nanoribbons. The vacant defects on both top and bottom edges in unpassivated armchair arsenene nanoribbon can make its current-voltage characteristic also present a negative differential resistance behavior. After expanding the areas of the top and bottom defects in unpassivated armchair arsenene nanoribbon, the peak-to-valley ratio of the negative differential resistance behavior can be enlarged obviously, which opens another way for the application of arsenene-based devices with a high switching ratio.     

Negative differential resistance in polymer molecular devices modulated with molecular length

We study the electronic transport properties of polymer molecular devices by applying first-principles method. The results show that the electronic transport properties depend on molecular length. Negative differential resistance can be observed and can be modulated with molecular length.     

Observation of room temperature negative differential resistance in solution synthesized ZnO nanorod

We report the observation of negative differential resistance (NDR) in solution synthesized ZnO nanorod. The ZnO nanorod was fabricated as a two terminal planar device using lithographically patterned Au electrodes. The measured current–voltage response of the device has shown a negative differential resistance behavior. The peak-to-valley current ratio of the NDR is found to be greater than 4. The mechanism of this observed NDR effect has been explained based on charge trapping and de-trapping at the nanoscale contacts. It is the first observation of negative differential resistance effect in solution synthesized ZnO nanorod.     

Low-bias negative differential resistance in combined nanostructure of two zigzag-edged trigonal graphenes

Using the density functional theory combined with the non-equilibrium Green's function method, we have investigated the electron transport properties of combined nanostructures of two zigzag-edged trigonal graphenes linked by their vertex carbon atoms bridged between two gold electrodes. The results show that obvious negative differential resistance behavior can be obtained at low bias (0.3 V) in such combined systems. The observed low-bias negative differential resistance behavior is analyzed by the bias-dependent transmission spectra, projected density of states, and voltage drop.     

Light-induced negative differential resistance effect in a resistive switching memory device

The negative differential resistance (NDR) effect was observed in a Pt/BiFeO₃/TiO₂/BiFeO₃/Pt memory cell by using light-illumination as extra stimulation. Further, the coexistence appearances and gradually becomes obvious when the device is exposed to light-illumination, which display an excellent stability and reversibility of the coexistence of NDR and resistive switching (RS) at room temperature. Through analysis of the physical conduction mechanism, it is expected that a large number of photo-generated charge carriers are induced under light-illumination on the surface and interface of the heterojunction is responsible for the appearance of this coexistence phenomenon. Importantly, the NDR effect is strengthened by the competition transfer of charge carrier in the polarized electric field under light-illumination. This work shows that the coexistence of light-modulated NDR and RS can deeply explore the potential applications of light-controlled multifunctional devices.     

金纳米线接触构型相关的双重负微分电阻与整流效应

运用第一性原理密度泛函理论(DFT)和非平衡格林函数(NEGF)方法, 研究了[111]Au纳米线与1, 4-二硫苯酚(DTB)构成的分子结的电子输运性质. 构建并优化不同的Au-DTB接触构型, 计算发现: 尖端顶位构型最利于电流输运; 非对称构型大多具有很好的整流特性(最大整流比为25.6); 部分结构出现双重负微分电阻(NDR)效应. 分析表明, 整流效应主要源于非对称接触构型两端S-Au键的稳定性差别; 尖端金原子与硫原子的耦合能级中, 近费米面的能级对低压区电子传输起主要作用; 电压增大, 离费米面较远的能级对输运起主导作用, DTB的本征能级也逐渐参与, 这一转变致使电流出现两峰一谷的双重NDR效应.     

Strong n-type molecule as low bias negative differential resistance device predicted by first-principles study

A first-principles study of the transport properties of two thiolated pentacenes sandwiching ethyl is performed. The thiolated pentacene molecule shows strong n-type characteristics when contact Ag lead because of low work function about metal Ag. A strong negative differential resistance (NDR) effect with large peak-to-valley ratio of 758% is present under low bias. Our investigations indicate that strong n- or p-type molecules can be used as low bias molecular NDR devices and that the molecular NDR effect based on molecular-level leaving not on molecular-level crossing has no hysteresis.     

Multiple spin-resolved negative differential resistance and electrically controlled spin-polarization in transition metal-doped [6]cycloparaphenylenes

In structure, a [n]cycloparaphenylene ([n]CPP) molecule is constructed by fully conjugated bent benzenes, i.e., hexangular rings. Based on first-principles calculations, the spin-dependent electronic transport of transition metal-doped CPP, X@[6]cycloparaphenylene (X@[6]CPP) (X?=?Fe, Co and Ni), contacted with Au electrodes is investigated. (Multiple) negative differential resistance (NDR) is observed for all the doping cases, suggesting it is the intrinsic feature of such systems. Due to the spin dependence of the NDR, electrical switch of the direction of spin polarization for a current is realized. Further analysis shows that it is the suppression of the transmission peaks around the Fermi level as the bias increases that results in the NDR. The suppression is caused by the decay of the local density of states on the scattering region. As electrically controlled spin polarization is a promising area in nanoelectronics, we believe our results would be quite beneficial to the development of spintronic devices.     

Negative differential thermal resistance in a double-chain system

Using nonequilibrium molecular dynamics simulations, we study the phenomenon of negative differential thermal resistance (NDTR) in a double-chain system. We investigate the dependence of NDTR on the external potential, inter- and intra-chain interaction and the system size. It is reported that the NDTR can occur in a small double-chain system with weak external potential and weak inter- and intra-chain interaction. We also present the influence of the external potential, inter- and intra-chain interaction and the system size on the heat current of the system through the phonon spectral analysis.     

Large negative differential resistance and rectifying performance modulated by contact sites in fused thiophene trimmer-based molecular devices

By applying density functional theory with non-equilibrium Green?s function formalism, we have carried out a theoretical study of the electron transport in fused thiophene trimmer-based molecular devices with ethylene connections at three different sites. The simulation results indicate that the electronic transport properties strongly depend on the contact sites. Negative differential resistance and rectifying behaviors occur simultaneously in the current–voltage curves when ethylene connects the fused thiophene trimer at one second-nearest site and one third-nearest site. A larger negative differential resistance occurs only when ethylene connects the fused thiophene trimer at two second-nearest sites.