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The spin-dependent transport properties of a porphine molecule linking with two zigzag-edged graphene nanoribbon (ZGNR) electrodes have been investigated by using the density of functional theory (DFT) combined with the non-equilibrium Green's function (NEGF) method. The device shows clearly negative differential resistance (NDR), large tunnelling magnetoresistance (TMR) of 103 magnitude and nearly 100% perfect spin filter efficiency (SFE) properties, respectively. What's more, the projected density of states (PDOS), molecular projected self-consistent Hamiltonian (MPSH) eigenvalues and transmission eigenstates were carried out to discuss the transport properties of the ZGNR/Porphine/ZGNR nanojunction. These results suggest that the ZGNR/Porphine/ZGNR device is a promising candidate for multi-functional spintronic devices. [ABSTRACT FROM AUTHOR]

A new and simple kind of all-carbon junction nanodevice, which is free of metal electrodes, is constructed by carbon chains seamlessly connected to two graphyne nanoribbons (GYNRs) electrodes. The electron transport properties of the constructed nanodevices are systematically investigated using self-consistent charge density-functional tight-binding combined with nonequilibrium Green’s function (NEGF) formalism. The effects of contact type and contact position on the electron transport properties of these devices are discussed. The calculated results show that the electron transport properties can be well modulated by the contact geometry of the carbon chain. In GYNRs connected by both horizontal and tilted single-carbon chain, an evident even–odd behavior of conductivity is observed. In addition, the linear, monotonous currents in a wide bias voltage range show good Ohmic contact. The negative differential resistance also appears under both positive and reverse bias voltages, indicating applications in bidirectional tunnel diodes. Comprehensive analyses of the physical mechanisms for the odd–even behavior are given. Remarkably, in GYNRs connected by double-carbon chains, a noticeable current stabilizer behavior occurs, suggesting that the graphyne nanodevices contacted with double-carbon chains can be used as a current stabilizer in circuits. This article provides valuable insight into all-carbon functional nanodevices. [ABSTRACT FROM AUTHOR]

Abstract Depending on the mobile species involved in the resistive switching process, redox random access memories and conductive bridge random access memories are widely studied with distinct switching mechanisms. Although the two resistance switching types have faithfully proved to be electrochemically linked in metal oxide‐based memristive devices, the corresponding photo‐induced transition has not yet been realized. Here, a photo‐induced transition through the integration of a graphene layer into a titanium oxide‐based memory device is demonstrated. Coupled with Raman mapping and an electron energy loss spectroscopy technique, the photo‐induced interaction at the heterostructure of graphene/titanium oxide are considered to dominate the transition process. Moreover, a negative differential resistance effect is observed by controlling the applied voltage, which can be credited to the saturation of trap centers (oxygen vacancies) and the increase of interfacial barrier at the graphene/titanium oxide heterojunction.

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]

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]

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]

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.

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]

Graphene and molybdenum disulfide are two-dimensional novel materials considered promising for nanoscale electronic devices. Due to high carrier mobility and in spite of lacking a bandgap, nanoscale graphene transistors have been demonstrated to reach a cut-off frequency above 400 GHz. The absence of bandgap in graphene leads to a remarkable band-to-band tunneling property in electron devices with negative differential resistance. Ultra-thin field-effect transistors fabricated with graphene as gate conducting channels have been shown experimentally to exhibit negative differential resistance (NDR) with widespread appeal for both digital and analog electronics. NDR devices like the Esaki p-n junction have been known to have applications for high frequency oscillators, fast logic switches, memories and low-power amplifiers. In this work, a semi-analytical model equation for transfer characteristics of graphene transistors is developed to successfully model the NDR. Data from three known experimental devices exhibiting NDR with gate length from 500 nm to 3 μm are shown to match well with theoretical modeled results. Numerical calculations using the model equation show that at a fixed gate bias, NDR can be modulated by tuning the value of contact resistance. The result also shows that separate onset of NDR in purely electron current or hole current can be modeled with this equation and matches experimental data. [ABSTRACT FROM AUTHOR]

Abstract: The electronic transport properties of the molecular device based on double‐cage fluorinated fullerene C20F18(NH)2C20F18 were studied theoretically. The results show that the device exhibits two negative differential resistance (NDR) peaks in its I‐V curve. The NDR peak under low bias voltage originates from the bias‐induced alignment of the molecular orbitals, and the conduction channel being suppressed at a certain bias voltage is the main reason for the NDR peak under a relatively high bias voltage. [ABSTRACT FROM AUTHOR]

Using density functional theory in combination with non-equilibrium Green's functions, we investigate the spin transport in two heterostructures of graphene and hexagonal boron-nitride ( h -BN) nanoribbons with C-B and C-N interfaces, respectively. Significant spin-filtering effect (over 80%) is observed in both C-B and C-N devices with bias ranging from 0 V to 0.3 V. Interestingly, the spin polarizations are opposite in these two devices, and prominent negative differential resistance (NDR) for both spin-up and spin-down currents is observed only in the C-N device. These findings provide insight into how the spin-transport properties of graphene/ h -BN nanoribbons can be impacted by different types of interfaces of the heterostructures. [ABSTRACT FROM AUTHOR]

The article presents comparison of structural and electrical properties of fluorinated graphene (FG), graphene oxide (GO), and graphene films functionalized with N-methylpyrrolidone (G-NMP). The obtained functionalized graphene films were continuous, having no ruptures, their thickness was 20-50 nm. Fluorinated films are formed from fluorinated areas and corrugated graphene islets. The size and shape of microstructures on G-NMP surfaces depend on the duration of NMP treatment. GO films demonstrate a rippled surface morphology. The resistance of all films of functionalized graphene exceeds that of pristine graphene films (several kilohms). GO and FG films exhibit dielectric properties. Current-voltage characteristics of FG demonstrate two features: stepwise current increase and negative differential resistance (NDR). Functionalized graphene can be used in flexible electronics, particularly in planar printing technologies. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

By applying non-equilibrium Green's functions (NEGF) in combination with tight-binding (TB) model, we investigate and compare the electronic transport properties of H-terminated zigzag graphene nanoribbon (H/ZGNR) and O-terminated ZGNR/H-terminated ZGNR (O/ZGNR–H/ZGNR) heterostructure under finite bias. Moreover, the effect of width and symmetry on the electronic transport properties of both models is also considered. The results reveal that asymmetric H/ZGNRs have linear I – V characteristics in whole bias range, but symmetric H-ZGNRs show negative differential resistance (NDR) behavior which is inversely proportional to the width of the H/ZGNR. It is also shown that the I – V characteristic of O/ZGNR–H/ZGNR heterostructure shows a rectification effect, whether the geometrical structure is symmetric or asymmetric. The fewer the number of zigzag chains, the bigger the rectification ratio. It should be mentioned that, the rectification ratios of symmetric heterostructures are much bigger than asymmetric one. Transmission spectrum, density of states (DOS), molecular projected self-consistent Hamiltonian (MPSH) and molecular eigenstates are analyzed subsequently to understand the electronic transport properties of these ZGNR devices. Our findings could be used in developing nanoscale rectifiers and NDR devices. [ABSTRACT FROM AUTHOR]

We show that recently fabricated Chevron-type graphene nanoribbons act as a monolithic superlattice structure. This is enabled by the large periodic unit cells with regions of different effective bandgaps in these nanoribbons, resulting in minibands and gaps in the density of states above the conduction band edge. Quantum transport calculations based on non-equilibrium Green’s function formalism reveal that a negative differential resistance (NDR) is expected to manifest in these nanoribbons. Due to the relatively low density of states, such NDR behavior can also be modulated with a gate electric field. We show that a sub-thermal subthreshold swing ( < \textit kT/q ) can potentially be obtained in a three-terminal configuration, even in the presence of optical phonon scattering. [ABSTRACT FROM AUTHOR]

By performing first-principle quantum transport calculations, we investigate the effects of connected position and B/N doping on the transport properties of a single cruciform diamine molecule connected to zigzag graphene nanoribbon leads. The negative differential resistance behaviors are found in I V characteristics of the undoped molecular device. The peak-to-valley current ratio can be modulated obviously by changing the connected position. Then, we find the B/N doped effects are sensitive to doping site in the connected region. The replacement of B/N atom on R1 (carbon atom in connected region close to the zigzag graphene nanoribbon) seldom affects the transmission spectrum around Fermi level. But, the replacement of B/N atom on R2 (carbon atom in connected region close to the molecule) can raise the transmission coefficient around Fermi level markedly leading to the large growth of the current at the low biases. In addition, the replacement of N atom on R2 can induce a negative differential resistance behavior in I V curve at low bias region. [ABSTRACT FROM AUTHOR]

We demonstrate gate-tunable resonant tunneling and negative differential resistance between two rotationally aligned bilayer graphene sheets separated by bilayer WSe2. We observe large interlayer current densities of 2 and 2.5 μA/μm² and peak-to-valley ratios approaching 4 and 6 at room temperature and 1.5 K, respectively, values that are comparable to epitaxially grown resonant tunneling heterostructures. An excellent agreement between theoretical calculations using a Lorentzian spectral function for the two-dimensional (2D) quasiparticle states, and the experimental data indicates that the interlayer current stems primarily from energy and in-plane momentum conserving 2D-2D tunneling, with minimal contributions from inelastic or non-momentum-conserving tunneling. We demonstrate narrow tunneling resonances with intrinsic half-widths of 4 and 6 meV at 1.5 and 300 K, respectively. [ABSTRACT FROM AUTHOR]

Hybridized Z-Be x S y C z ( x + y + z = 16 ) systems connected by zigzag beryllium-sulfide (BeS) and graphene nanoribbons are theoretically designed, and their electronic transport characteristics are explored by first-principles approach. For the hybridized systems with unequal number of x and y , i.e. z is an odd number, an exceptional negative differential resistance (NDR) property occurs. However, for the hybridized systems including an even number of zigzag carbon chains, namely x equal to y , an interesting current-limited behavior happens. Meanwhile, the NDR phenomenon disappears. The spin transport properties of these hybridized Z-Be x S y C z systems with parallel magnetism configuration also reveal the above odd–even dependence conductance behavior. [ABSTRACT FROM AUTHOR]

In this study, we investigated the spin-resolved transport aspects of step-like zigzag graphene ribbons (ZGNRs) with single or double edge-saturated hydrogen using a method that combined the density functional theory with the nonequilibrium Green's function method under the local spin density approximation. We found that, when the ZGNR-based heterojunctions were in a parallel or antiparallel layout, negative differential resistance, the maximum bipolar spin-filtering, and spin-rectifying effects occurred synchronously except for the case of spin-down electrons in the parallel magnetic layouts. Interestingly, these spin-resolved transport properties were almost unaffected by altering the widths of the two component ribbons. Therefore, step-like ZGNR heterojunctions are promising for use in designing high-performance multifunctional spintronic devices. [ABSTRACT FROM AUTHOR]

In this work, nanojunctions consisting of two combined similar right triangle graphenes (SRTGs) bonded covalently with zigzag-edged graphene nanoribbon electrodes are designed, and their electron transport properties are investigated using density functional theory and non-equilibrium Green's function method. Results reveal that the SRTG-based devices exhibit an interesting negative differential resistance (NDR) effect and present a rule indicating that the NDR effect increases with the increasing sizes of both SRTGs. The electron transport properties are further tested using two combined SRTGs with different sizes. Overall, this study suggests that the SRTG-based structures are promising candidates in the design of nanoscale NDR devices. [ABSTRACT FROM AUTHOR]

The distinct negative differential resistance (NDR) mechanism arising from interlayer angular rotation in three-terminal graphene-BN heterostructures, as a function of both the twisting angle and the gate bias, is simulated and analyzed. Analytical expressions for the positions of the NDR peaks in the $I$ – $V$ characteristics are developed. To capture the degradation of peak-to-valley ratios observed in experiment at room temperature, electron–phonon scattering has been added to the simulation and good agreement with experiment is achieved. Our simulation also shows a robust preservation of NDR feature when temperature increases. [ABSTRACT FROM PUBLISHER]

The organic molecule deposited between gaphene electrodes to form a molecular device has been demonstrated experimentally. Motivated by this case, devices consisting of the polyphenylene molecule bonded covalently with armchair-edged graphene nanoribbon (AGNR) electrodes are constructed and the selective doping with N atom is considered theoretically. Our modeling calculations show that such devices hold the nonlinear and doping-site-dependent transport properties, prominently with multi-peak NDR (negative differential resistance) effect. And, for a peculiar doping site, a very large NDR can be observed, which could be attributed to interactions of the molecular core and doped AGNR electrodes, namely, these hybridized wave functions hold distinctly different delocalization in different benzene rings of the polyphenylene molecule when the applied bias is altered. Also shown is that this large NDR is robust regarding the length increasing and rotation of molecule. [ABSTRACT FROM AUTHOR]

Based on the nonequilibrium Green's function method and density functional theory calculations, we investigate the electronic transport properties of a single chiroptical molecular switch with two zigzag graphene nanoribbon electrodes. The molecule undergoing the switch can exhibit different chirality namely cis -isomer and trans -isomer by ultraviolet or visible irradiation. Theoretical results clearly reveal that these two isomers exhibit very different current – voltage characteristics, which can realize the switching behaviors when the molecule converts between cis -isomer and trans -isomer. Furthermore, the negative differential resistance behaviors also can be observed in these two isomers, suggesting potential applications of this type of junctions in future design of functional molecular devices. [ABSTRACT FROM AUTHOR]

Employing nonequilibrium Green's Functions in combination with density functional theory, the electronic transport properties of armchair graphene nanoribbon (GNR) devices with various widths are investigated in this work. In the adopted model, two semi-infinite graphene electrodes are periodically doped with boron or nitrogen atoms. Our calculations reveal that these devices have a striking nonlinear feature and show notable negative differential resistance (NDR). The results also indicate the diode-like properties are reserved and the rectification ratios are high. It is found the electronic transport properties are strongly dependent on the width of doped nanoribbons and the positions of dopants and three distinct families are elucidated for the current armchair GNR devices. The NDR as well as rectifying properties can be well explained by the variation of transmission spectra and the relative shift of discrete energy states with applied bias voltage. These findings suggest that the doped armchair GNR is a promising candidate for the next generation nanoscale device. [ABSTRACT FROM AUTHOR]

The magnetic and spin transport properties of asymmetric edge-hydrogenated zigzag graphene nanoribbons (ZGNRs) selectively doped with nitrogen atoms were investigated using spin-polarized density functional theory and non-equilibrium Green's function. Results show that the rectifying performance of spin-polarized current with a ratio higher than 10 can be modulated by changing the positions of the nitrogen dopant. Complete spin filtering (100%) and excellent negative differential resistance behaviors were observed in the ZGNR junctions. These doping position-dependent spin transport characteristics were further tested by shifting from the odd-numbered zigzag-shaped C chains ( N) to the even-numbered N in ZGNRs. This study suggests that adopting a suitable nitrogen doping position could be an effective approach to significantly enhance the rectifying behavior of asymmetric edge-hydrogenated ZGNRs, which are promising materials for multifunctional spintronic devices. [ABSTRACT FROM AUTHOR]

By applying nonequilibrium Green's functions in combination with the density-functional theory, we investigate the electron transport properties of the salicylideneaniline molecule sandwiched between two armchair graphene nanoribbon (AGNR) electrodes. It shows that the width of the AGNR electrodes plays a significant role in the transport properties of the salicylideneaniline molecular junctions. The current–voltage characteristics of the salicylideneaniline molecule sandwiched between 8AGNR electrodes can perform a stable conductance switching behavior at the bias region [1.2 V, 1.6 V] when the molecule translates between the trans -enol form and the trans -keto form. When the electrodes change to 7AGNR, a remarkable negative differential resistance behavior can be found in the salicylideneaniline molecular device at the trans -keto form. That means the salicylideneaniline molecule can perform different functions when it connects to the different AGNR electrodes. [ABSTRACT FROM AUTHOR]

The telescopic contact between graphene layers with a dielectric spacer is considered as a new type of graphene-based nanoelectronic devices. The tunneling current through the contacts with and without an argon spacer is calculated as a function of the overlap length, stacking of the graphene layers and voltage applied using non-equilibrium Green function formalism. A negative differential resistance (similar to semiconductor tunnel diode) is found with the peak to valley ratio up to 10 and up to 2 for the contacts without any spacer and with the argon spacer, respectively. The capacitance of the contacts between the graphene layers with the argon spacer is calculated as a function of temperature taking into account the quantum contribution. The related RC time constant is estimated to be about 3 ps, which allows elaboration of fast-response nanoelectronic devices. The possibility of application of the contacts as memory cells is discussed. [ABSTRACT FROM AUTHOR]

This paper presents the study of Gallium and Aluminum doped Nitrogen terminated zigzag Graphene Nano Ribbon (GNR) FET with high-k dielectric. The GNR FET structure has been designed and simulated using Quantumwise Atomistix Toolkit software package. The presented GNR FET with n-type (Nitrogen doped) electrodes and p-type (Gallium or Aluminum doped) scattering region are simulated and analyzed using Density Functional Theory combined with NEGF formalism and Device Density of States (DDOS). The device shows a negative differential resistance phenomenon which can be controlled by the gate of the zigzag GNR FET. It is found that doping of Gallium and Aluminum in scattering region provides higher drain current, higher I ON / I OFF and I P / I V ratios as compared to that of Boron doped zigzag GNR FET. The potential applications of the device are in logical, high frequency, and memory devices. [ABSTRACT FROM AUTHOR]

Graphene is an emerging nanomaterial believed to be a potential candidate for post-Si nanoelectronics due to its exotic properties. Recently, a new graphene nanoribbon crossbar (xGNR) device was proposed which exhibits negative differential resistance (NDR). In this article, a multistate memory design is presented that can store multiple bits in a single cell enabled by this xGNR device, called graphene nanoribbon tunneling random access memory (GNTRAM). An approach to increase the number of bits per cell is explored alternative to physical scaling to overcome CMOS SRAM limitations. A comprehensive design for quaternary GNTRAM is presented as a baseline, implemented with a heterogeneous integration between graphene and CMOS. Sources of leakage and approaches to mitigate them are investigated. This design is extensively benchmarked against 16nm CMOS SRAMs and 3T DRAM. The proposed quaternary cell shows up to 2.27× density benefit versus 16nm CMOS SRAMs and 1.8× versus 3T DRAM. It has comparable read performance and is power efficient up to 1.32× during active period and 818× during standby against high-performance SRAMs. Multistate GNTRAM has the potential to realize high-density low-power nanoscale embedded memories. Further improvements may be possible by using graphene more extensively, as graphene transistors become available in the future. [ABSTRACT FROM AUTHOR]

We investigate the electronic transport properties of triangular graphene systems with atoms B , N or both of them vertex doped based on non-equilibrium Green’s function approach combined with density functional theory. Interestingly, fine rectifying behavior and obvious negative differential resistance are observed in B – N vertex doped case. The origin of the rectification is that a barrier likes a p – n junction has been formed in B – N vertex doped junction. Moreover, weak interaction is considered by adjusting the distance between the two intermediate atoms. With the increase of the distance between them, the rectifying behavior and negative differential resistance weaken step by step. Our structure constructed by B – N vertex doped triangular graphene to realize fine rectification is constructive and is a promising candidate for the next generation nanoscale device. [ABSTRACT FROM AUTHOR]

Based on the non-equilibrium Green's function (NEGF) method combined with the density functional theory (DFT), we have studied the gate-modulated electronic properties of a graphene nanoribbon (GNR) which is composed of two GNRs of different widths. The results show that the charge transport is greatly modulated by the applied gate. Negative differential resistance (NDR) behaviors is found in such a system. With the increase in the gate, the NDR behaviors will disappear and reappear. Furthermore, under certain gate voltages multiple NDR behavior is found, the origin of which is attributed to the change of the number of effective transport channels and the variation of delocalization degree of the orbitals within the bias window. Interestingly, low bias NDR behavior is obtained which is desirable for integrated circuits from the point view of power consumption. We have studied the gate-modulated electronic properties of a graphene nanoribbon (GNR) which is composed of two GNRs of different widths. The results indicate that the charge transport is greatly modulated by the applied gate. Interestingly, low bias NDR behavior is obtained which is desirable for integrated circuits from the point view of power consumption. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: By applying the nonequilibrium Greenʼs 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. [Copyright &y& Elsevier]

In this paper, we clarify the physical mechanism for the phenomenon of negative output differential resistance (NDR) in short-channel graphene FETs through nonequilibrium Green's function simulations and a simpler semianalytical ballistic model that captures the essential physics. This NDR phenomenon is due to a transport mode bottleneck effect induced by the graphene Dirac point in the different device regions, including the contacts. NDR is found to occur only when the gate biasing produces an n-p-n or p-n-p polarity configuration along the channel, for both positive and negative drain–source voltage sweep. In addition, we also explore the impact on the NDR effect of contact-induced energy broadening in the source and drain regions and a finite contact resistance. [ABSTRACT FROM AUTHOR]

We propose, fabricate, and experimentally demonstrate a circuit based on graphene field-effect transistors (GFETs) showing enhanced negative differential resistance (NDR) characteristics at room temperature. The proposed graphene NDR (GNDR) circuit consists of three GFETs, which includes a two GFET inverter connected in a feedback loop with the main GFET in which the NDR is realized. Herein, a GNDR circuit is demonstrated using large-area chemical vapor deposition grown graphene and no doping step, which makes it compatible with silicon-based circuits. The circuit shows negative differential conductance (2.1 mS/ \mu \textm ) that is almost an order of magnitude better than NDR based on 1-GFET. This conductance level is uniquely tunable ( $\times 2.3$ ) with the supply voltage as well as with the back bias voltage. It also exhibits an improved peak-to-valley current ratio (2.2) and a wide voltage range (0.6 V) over which NDR is valid. In comparison with other NDR technologies, the GNDR has a very high peak-current-density of the order of 1 mA/ \mu \textm , which offers unique opportunities for designing circuits for applications requiring high current drive. [ABSTRACT FROM AUTHOR]

We present the room temperature operation of a vertical tunneling field-effect transistor using a stacked double bilayer graphene (BLG) and hexagonal boron nitride heterostructure. The device shows two tunneling resonances with negative differential resistance (NDR). An analysis of the electrostatic potential drop across the heterostructure indicates the resonances are associated with the relative alignment of the lower or upper bands of the two BLG. Using the NDR characteristic of the device, one-transistor latch or SRAM operation is demonstrated. The device characteristics are largely insensitive to temperature from 1.5 to 300 K. [ABSTRACT FROM AUTHOR]

This paper investigates the electronic transport properties in tailored triangular zigzag graphene nanoribbons (ZGNRs) with different orientations by applying density functional theory (DFT) based non-equilibrium Green's function method. It can be seen from the results calculated, the orientation of the triangular structure has a great effect on deciding the capacity to transport electrons of the molecular device. From different I - V characteristic curves, an upward and rightward triangular graphene can control the molecular switch on and off states. The peak value of on - off ratio can be 350 at 0.9 V. Furthermore, there is a remarkable negative differential resistance behaviors for the molecular device with upward triangular graphene, indicating that this system will have a widely applied in future molecular devices designs. [ABSTRACT FROM AUTHOR]

Depending on the mobile species involved in the resistive switching process, redox random access memories and conductive bridge random access memories are widely studied with distinct switching mechanisms. Although the two resistance switching types have faithfully proved to be electrochemically linked in metal oxide‐based memristive devices, the corresponding photo‐induced transition has not yet been realized. Here, a photo‐induced transition through the integration of a graphene layer into a titanium oxide‐based memory device is demonstrated. Coupled with Raman mapping and an electron energy loss spectroscopy technique, the photo‐induced interaction at the heterostructure of graphene/titanium oxide are considered to dominate the transition process. Moreover, a negative differential resistance effect is observed by controlling the applied voltage, which can be credited to the saturation of trap centers (oxygen vacancies) and the increase of interfacial barrier at the graphene/titanium oxide heterojunction. [ABSTRACT FROM AUTHOR]