Differential Resistance Behavior Research Articles

Interface-induced negative differential resistance and memristive behavior in Gr/MoSe2 heterostructure

Interface-induced negative differential resistance and memristive behavior in Gr/MoSe2 heterostructure

Theoretical investigation of electron transport properties in organic functional isomers - Ab initio study

Understanding the electron transport in metal-molecule-metal junctions provide a deeper insight into molecular electronics. We have performed a first principle analysis using Density Functional Theory (DFT) with Non-Equilibrium Green's Function (NEGF) to study the electron transport properties of functional isomers (benzyl alcohol and p-cresol). To understand the electron transport through these molecules we have constructed a metal-molecule-metal junction by sandwiching benzyl alcohol or p-cresol molecule with gold electrodes through a sulfur atom which acts as a linker between the electrode and the molecule. At zero bias the density of states and the projected density of states of these molecules remains the same between −1 eV and 1 eV energy levels. The transmission coefficient of the benzyl alcohol is higher than p-cresol at higher energy levels at zero bias. Current-voltage characteristic shows the differential resistance effect presents in these molecules. At higher bias region, benzyl alcohol molecular junction shows higher conductance than p-cresol molecular junction. Further, current density across the device was calculated to get an insight into the differential resistance behavior in these molecules. From this analysis, we conclude that these molecules can be used for several electronic applications such as switches, oscillators etc.

Gate-modulated electronic transport through a graphene nanoribbon composed of nanoribbons of different widths

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.

Tuning electron transport through a single molecular junction by bridge modification

The possibility of controlling electron transport in a single molecular junction represents the ultimate goal of molecular electronics. Here, we report that the modification of bridging group makes it possible to improve the performance and obtain new functions in a single cross-conjugated molecular junction, designed from a recently synthesized bipolar molecule bithiophene naphthalene diimide. Our first principles results show that the bipolar characteristic remains after the molecule was modified and sandwiched between two metal electrodes. Rectifying is the intrinsic characteristic of the molecular junction and its performance can be enhanced by replacing the saturated bridging group with an unsaturated group. A further improvement of the rectifying and a robust negative differential resistance (NDR) behavior can be achieved by the modification of unsaturated bridge. It is revealed that the modification can induce a deviation angle about 4° between the donor and the acceptor π-conjugations, making it possible to enhance the communication between the two π systems. Meanwhile, the low energy frontier orbitals of the junction can move close to the Fermi level and encounter in energy at certain biases, thus a transport channel with a considerable transmission can be formed near the Fermi level only at a narrow bias regime, resulting in the improvement of rectifying and the robust NDR behavior. This finding could be useful for the design of single molecular devices.

Position effects of single vacancy on transport properties of single layer armchair h-BNC heterostructure

Based on certain single layer armchair h-BNC heterostructures, six molecular devices with different positions of single vacancy atoms are investigated to explain the modulating process of negative differential resistance (NDR) behaviors and rectifying performance. The results show that NDR behaviors can be observed clearly with vacancy atoms near the interface of graphene nano-ribbon and BN nano-ribbon, and rectifying performance can be enhanced obviously when there are vacancy atoms in the moiety of the BN nano-ribbon. The first-principles analysis of the microscopic nature reveals that strength of electronic transmission, evolutions of molecular orbitals and distributions of molecular states are the intrinsic responses to these transport properties.

Electronic transport through a C60– n X n (X=N and B) molecular bridge

By applying the non-equilibrium Green's function (NEGF) technique, the Landauer–Buttiker theory and the Fisher–Lee formula, we have investigated the transport behavior of a C60– n X n (X=N, B) molecule coupled to two semi-infinite SWCNT electrodes. In this study, the coupling through the carbon, boron and nitrogen atoms to the electrodes will be considered. We study the effects of different contact geometries, the electron–phonon interaction and the number of doped atoms on the current value and negative differential resistance (NDR) behavior of C60– n X n . Our results indicate that the transmission coefficient and the NDR behavior of C60– n X n vary on changing n and X. Moreover, NDR behavior is observed in C60– n X n with different contacts and in C60 with C5 and C6 contacts. C60– n X n molecules are suggested for the operation of devices with a nanoscale current.

Scanning Tunneling Microscopy and Tunneling Spectroscopy of Nano-structured H<SUB>6</SUB>P<SUB>2</SUB>Mo<SUB><I>x</I></SUB>W<SUB>18−<I>x</I></SUB>O<SUB>62</SUB> (<I>x</I> = 0, 3, 9, 15, 18) Wells-Dawson Heteropolyacids

Scanning tunneling microscopy (STM) and tunneling spectroscopy studies of nano-structured H6P2MoxW(18-x)O62 (x = 0, 3, 9, 15, 18) Wells-Dawson heteropolyacids (HPAs) were carried out to examine redox properties of the HPAs. STM images of H6P2MoxW(18-x)O62 HPAs clearly showed self-assembled and well-ordered 2-dimensional arrays on graphite surface. Tunneling spectroscopy measurements revealed that all H6P2MoxW(18-x)O62 HPAs exhibited a negative differential resistance (NDR) behavior in their tunneling spectra. NDR peak voltage of H6P2MoxW(18-x)O62 HPAs appeared at less negative applied voltage with increasing molybdenum substitution. Reduction potential of H6P2MoxW(18-x)O62 HPAs measured by an electrochemical method increased and absorption edge energy determined by UV-visible spectroscopy shifted to lower value with increasing molybdenum substitution. In other words, NDR peak voltage of H6P2MoxW(18-x)O62 HPAs appeared at less negative applied voltage with increasing reduction potential and with decreasing absorption edge energy of the HPAs; more reducible H6P2MoxW(18-x)O62 HPAs showed NDR behavior at less negative applied voltage. These results indicate that NDR peak voltage of nano-structured HPAs measured by STM could be utilized as a correlating parameter for the redox properties of bulk HPAs.

Negative differential resistance in parallel single-walled carbon nanotube contacts

Based on first-principles calculations, we investigate the electron transport properties of parallel single-walled carbon nanotube contact. A significant negative differential resistance (NDR) behavior is found due to staggered electron gratings in energy space and standing waves in real space on the two tubes induced by bias. Such a NDR effect is robust against the contact length, the tube diameter, the shape of the end, and the difference in the two electrodes. Because no bridging molecule is used, the structure of this NDR device is simpler compared with ordinary molecular NDR devices. Our findings are expected to promote the discovery of more NDR devices composed of only two electrodes in parallel contact.

An <i>Ab Initio</i> Study on Negative Differential Resistance in Pyrrole Trimer Molecular Device

The electronic transport properties of pyrrole trimer sandwiched between two electrodes are investigated by using nonequilibrium Green’s function formalism combined first-principles density functional theory. Theoretical results show that the system manifests negative differential resistance (NDR) behavior. A detailed analysis of the origin of negative differential resistance has been given by observing the shift in transmission resonance peak across the bias window with varying bias voltage.

Oriented Gold Nanoparticle-Polyaniline Nanorods with Nanofibers of Controlled Density on Their Surface

We report here the preparation of fibrous gold nanoparticles-polyaniline (PANI) nanorod composite as an extension of our previous work in nanostructured conducting polymers. We have been able to control the amount of gold particles and the density of nanofibers covering the surface of the nanorods, which are characterized by selected area electron diffraction (SAED), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The morphology of PANI products is confirmed by both scanning electron microscopy (SEM) and TEM. The effect of reaction conditions on the morphology of PANI nanostructures is also studied. The chemical and electronic structures of the PANI nanorods are determined by Fourier transform IR (FTIR) and UV-vis spectrometry. I-V curves of as-prepared PANI nanostructures measured by conductive atomic force microscopy (c-AFM) indicate negative differential resistance (NDR) behavior.

Multi-peak negative differential resistance device consisting of multiple quantum dots sandwiched between two metallic electrodes

We investigate tunneling current through a set of coupled quantum dots at finite temperature. We found that the multi-peak negative differential resistance (NDR) behavior can be generated by manipulating the tunneling current though the multiple quantum dots. Such an NDR effect is suppressed by the temperature. It is shown that for a three-dot case, a large peak-to-valley ratio of tunneling current exists in the condition of dot A with symmetrical tunneling rates and dot B and dot C with the shell-filling tunneling rate ratios.

Proximity effect in planar TiN-Silicon junctions

We measured the low temperature subgap resistance of titanium nitride (superconductor, T c=4.6 K)/highly doped silicon (degenerated semiconductor) SIN junctions, where I stands for the Schottky barrier. At low energies, the subgap conductance is enhanced due to coherent backscattering of the electrons towards the interface by disorder in the silicon (“reflectionless tunneling”). This Zero Bias Anomaly (ZBA) is destroyed by the temperature or the magnetic field above 250 mK or 0.04 T respectively. The overall differential resistance behavior (vs temperature and voltage) is compared to existing theories and values for the depairing rate and the barrier transmittance are extracted. Such an analysis leads us to introduce an effective temperature for the electrons and to discuss heat dissipation through the SIN interface.

Quantum Transport Through Intermolecular Nanotube Junctions

AbstractQuantum transport properties of intermolecular nanotube contacts are investigated. We find that atomic structure in the contact region plays important roles and resistance of contacts varies strongly with geometry and nanotube chirality. Nanotube end-end contacts have low resistance and show negative differential resistance (NDR) behavior. Exerting small pressure/force between the tubes can dramatically decrease contact resistance, if the contact is commensurate. Significant variation and nonlinearity of contact resistance may lead to new device applications.