Low-bias Negative Differential Resistance Research Articles

Low-bias negative differential resistance effect in armchair graphene nanoribbon junctions

Graphene nanoribbons with armchair edges (AGNRs) have bandgaps that can be flexibly tuned via the ribbon width. A junction made of a narrower AGNR sandwiched between two wider AGNR leads was recently reported to possess two perfect transmission channels close to the Fermi level. Here, we report that by using a bias voltage to drive these transmission channels into the gap of the wider AGNR lead, we can obtain a negative differential resistance (NDR) effect. Owing to the intrinsic properties of the AGNR junctions, the on-set bias reaches as low as ∼0.2 V and the valley current almost vanishes. We further show that such NDR effect is robust against details of the atomic structure of the junction, substrate, and whether the junction is made by etching or by hydrogenation.

Modulation of Low Bias Negative Differential Resistance in a Molecular Device by Adjusting Anchoring Groups

We investigate electronic transport properties of molecular device models constructed by a dipyrimidinyl–dimethyl molecule embedding in a carbon chain, which are then coupled to the gold electrodes through thiol or isocyanide group. Using the density functional theory combined with the nonequilibrium Green’s function method, negative differential resistance behaviors are observed in such molecular junctions. Most importantly, system with the isocyanide group can achieve a larger negative differential resistance at lower bias voltage (0.1V).

Tip-contact related low-bias negative differential resistance and rectifying effects in benzene-porphyrin-benzene molecular junctions.

The electronic transport properties of benzene-porphyrin-benzene (BPB) molecules coupled to gold (Au) electrodes were investigated. By successively removing the front-end Au atoms, several BPB junctions with different molecule-electrode contact symmetries were constructed. The calculated current-voltage (I-V) curves depended strongly on the contact configurations between the BPB molecules and the Au electrodes. In particular, a significant low-voltage negative differential resistance effect appeared at -0.3 V in the junctions with pyramidal electrodes on both sides. Along with the breaking of this tip-contact symmetry, the low-bias negative differential resistance effect gradually disappeared. This tip-contact may be ideal for use in the design of future molecular devices because of its similarity with experimental processes.

Contact transparency inducing low bias negative differential resistance in two capped carbon nanotubes sandwiching σ barrier

A first-principles study of the transport properties of two capped (5, 5) carbon nanotubes sandwiching σ barrier is reported. Contact transparency at zero bias is obtained. Strong negative differential resistance effect with large peak-to-valley ratio of 1,124 % is present under very low bias, which may promise the potential applications in nano-electronic devices with low power dissipation in the future.

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 104–106 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.

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.

First-Principles Study of the Rectifying Properties of the Alkali-Metal-Atom-Doped BDC60 Molecule

We investigated the effect of alkali-metal-atom doping on the electronic transport properties of BDC60 molecules, using a combination of first-principles density-functional theory and the non-equilibrium Green′s function. Our calculation results show that alkali-metal-atom-doped BDC60 molecules exhibit good rectifying and negative differential resistance behaviors at very low bias. The intrinsic mechanisms for these phenomena are discussed systematically in terms of the transmission spectra and frontier molecular orbitals, as well as their spatial distributions under various external applied biases. Our study will help in developing future applications of BDC60 molecules in low-bias rectifying and negative differential resistance molecular devices.

Controllable low-bias negative differential resistance, switching, and rectifying behaviors of dipyrimidinyl–diphenyl induced by contact mode

The negative differential resistance (NDR) and the rectifying behaviors of a molecular device induced by a saturated hydrogen atom and contact modes are investigated. Results reveal low-bias NDR behaviors of dipyrimidinyl–diphenyl (DD) molecule without saturated H atoms. NDR behavior can be eliminated depending on the contact sites. However, the rectifying behaviors of DD-molecule with saturated H atoms are apparent for all considered contact modes. In addition, the possible contact mode of the molecule in the experiment [12] was identified by examining the effect of molecular adsorption sites on gold electrodes and saturated hydrogen atom on conductance. The mechanism underlying various properties are analyzed with the highest occupied molecular orbital, lowest unoccupied molecular orbital, and transmission spectra.

Low bias negative differential resistance in C60 dimer modulated by gate voltage

By using a combined method of density functional theory and nonequilibrium Green’s function formalism, we investigate the electronic transport properties of a gated C60 dimer molecule sandwiched between two gold electrodes. The results show that the gate voltage can strongly affect the electronic transport properties of the C60 dimer and change it from semiconducting to metallic. Negative differential resistance behaviors are obtained in such systems and can be modulated to occur at much lower bias by the gate voltage. The low bias negative differential resistance is analyzed from the calculated transmission spectra, projected density of states and the spatial distribution of molecular projected self-consistent Hamiltonian orbitals along with the voltage drop. These results provide a theoretical support to the design of low bias negative differential resistance molecular device by using the modulation of gate voltage.

Controllable low-bias negative differential resistance and rectifying behaviors induced by symmetry breaking

Incorporating the characteristic of pyramidal electrode and symmetry breaking of molecular structure, we theoretically design a molecular device to perform negative differential resistance and rectifying behaviors simultaneously. The calculated results reveal that low-bias negative differential resistance behaviors can appear symmetrically when tetraphenyl molecule connects to pyramidal gold electrodes. However, as one phenyl of tetraphenyl molecule is replaced by a pyrimidyl, the symmetry breaking on the molecule will break the symmetry of negative differential resistance behavior. The peak-to-valley ratio on negative bias region is larger than that on positive bias region to perform a low-bias rectifying behavior. More importantly, increasing the symmetry breaking can further weaken these two behaviors which propose an effective way to modulate them.

Giant low bias negative differential resistance induced by nitrogen doping in graphene nanoribbon

By applying nonequilibrium Green’s function formalism in combination with density functional theory, we have investigated the electronic transport properties of armchair graphene nanoribbon devices with periodic nitrogen-doping. Giant negative differential resistance behaviors with peak-to-valley ratio up to the order of 105 can be obtained in the mV bias regime by tuning the position and the concentration of the dopants. The negative differential resistance behavior is understood in terms of the evolution of the transmission spectrum and band structures with applied bias combined with the symmetry analyses of the Bloch wave functions of the corresponding subbands.

Low Bias Negative Differential Resistance with Large Peak-to-Valley Ratio in a BDC60 Junction

Based on nonequilibrium Green's function method and density functional theory calculations, we investigate theoretically the electronic transport properties of 1,4-bis(fullero[c]pyrrolidinl-yï)benzene (BDC60). A low bias negative differential resistance with the peak-to-valley ratio as high as 305.41 is obtained. The observed negative differential resistance is explained in terms of the evolution of the transmission spectra, molecular projected self-consistent Hamiltonian states and molecular projected energy levels with applied bias.

Large Low Bias Negative Differential Resistance in an Endohedral Li@C60 Dimer Junction

By applying the nonequilibrium Green function formalism combined with density functional theory, we have investigated the electronic transport properties of the C60 dimer and its endohedral complex Li@C60 dimer. Our results show that the doping of Li atoms significantly changes the transport properties of the C60 dimer. Negative differential resistance is found in such systems. Especially, the doping of Li atoms can lead to a much larger negative differential resistance at much lower bias, and it is quite evident from the plot of differential conductance versus bias. The negative differential resistance behavior is understood in terms of the evolution of the transmission spectrum and projected density of states spectrum with applied bias combined with molecular projected self-consistent Hamiltonian states analyses.

Low-bias negative differential resistance in graphene nanoribbon superlattices

We theoretically investigate negative differential resistance (NDR) for ballistic transport in semiconducting armchair graphene nanoribbon (aGNR) superlattices (5 to 20 barriers) at low bias voltages ${V}_{\mathrm{SD}}<500$ mV. We combine the graphene Dirac Hamiltonian with the Landauer-B\"uttiker formalism to calculate the current ${I}_{\mathrm{SD}}$ through the system. We find three distinct transport regimes in which NDR occurs: (i) a ``classical'' regime for wide layers, through which the transport across band gaps is strongly suppressed, leading to alternating regions of nearly unity and zero transmission probabilities as a function of ${V}_{\mathrm{SD}}$ due to crossing of band gaps from different layers; (ii) a quantum regime dominated by superlattice miniband conduction, with current suppression arising from the misalignment of miniband states with increasing ${V}_{\mathrm{SD}}$; and (iii) a Wannier-Stark ladder regime with current peaks occurring at the crossings of Wannier-Stark rungs from distinct ladders. We observe NDR at voltage biases as low as 10 mV with a high current density, making the aGNR superlattices attractive for device applications.