Multi-peak Negative Differential Resistance Research Articles

Pure valley current and negative differential resistance in optoelectronic superlattices based on monolayer transition metal dichalcogenides

We investigate the possibility of achieving valley filtering and enhanced negative differential resistance (NDR) in transition metal dichalcogenide (TMD)-based optoelectronic superlattice (SL). The multipeak NDR is predicted to occur in this system, the operation window of which is controlled successively by the resonant tunneling through miniband regime and the Wannier-Stark ladder regime. It is shown that the synergy of the electric and light stimulus can bring the pure valley current and pronounced peak-to-valley current ratio (PVCR). Our findings illustrate the origin of multipeak responses and provide a theoretical basis for designing devices that can generate pure valley current with complex NDR characteristics.

Electronic transport properties of heterojunction Pb/Pb-Si nanochain devices

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.

Multi-peak negative differential resistance in silicene superlattice: Toward multi-valued silicene logic devices

Negative differential resistance (NDR) in two dimensional materials has been the subject of strong interest for ultra-low power nanoelectronic applications. Here, we report NDR characteristics of silicene superlattice (SL) at low bias voltages. Transport process manipulated by miniband regime for low bias region and Wannier-Stark (WS) ladders regime with multi-peak NDR for higher bias windows. Local tunneling peaks rise from hybridization of Wannier-Stark rungs in certain bias voltages. The bias position of WS states crossings down shifted with increasing device dimension leading to red shifted NDR window and increases peak to valley ratio (PVR) values. The multiple NDR windows are represented by changing the size and the number of well/barriers in silicene SL. Maximum PVR of 8 obtained for device with low height barriers. Multi-peak NDR with same PVR values in very low bias regime can find key applications in multi-valued memories with low static power dissipation.

Negative differential resistance in partially fluorinated graphene films

Partially fluorinated graphene films were created by chemical functionalization of graphene layers in an aqueous solution of hydrofluoric acid. The formation of graphene islands or graphene quantum dots (GQDs) and a fluorinated graphene network is demonstrated in such films. Negative differential resistance (NDR) resulting from the formation of the potential barrier system in the films was observed for different fluorination degrees of suspension. The origin of the NDR varies with an increase in the fluorination degree of the suspension. Numerical calculations were performed to elucidate the tunneling between adjacent energy levels and creation of NDR. It was found that in the case of films with smaller flake and smaller GQD sizes, multi-peak NDR appears in the I–V curve. We predict that the NDR peak position shifts towards lower voltage with a decrease in the GQD size. Surprisingly, we observed a negative step-like valley for positive biases in the I-V curve of samples. Our findings with detailed analysis shed light on understanding the mechanisms of the NDR phenomenon in a partially fluorinated graphene system.

Robust low-bias negative differential resistance in graphene superlattices

In this work, we present a detailed theoretical study on the low bias current–voltage (I–V) characteristic of biased planar graphene superlattice (PGSL), provided by a heterostructured substrate and a series of grounded metallic planes placed over a graphene sheet, which induce a periodically modulated Dirac gap and Fermi velocity barrier, respectively. We investigate the effect of PGSL parameters on the I–V characteristic and the appearance of multipeak negative differential resistance (NDR) in the proposed device within the Landauer–Buttiker formalism and adopted transfer matrix method. Moreover‚ we propose a novel venue to control the NDR in PGSL with Fermi velocity barrier. Different regimes of NDR have been recognized, based on the PGSL parameters and external bias. From this viewpoint‚ we obtain multipeak NDR through miniband aligning in PGSL. The maximum pick to valley ratio (PVR) up to 167 obtained for , the Fermi velocity correlation (ratio of Fermi velocity in barrier and well region), is 1.9 at bias voltages between 70–130 mV. Our findings have good agreement with experiments and can be considered in designing multi-valued memory‚ functional circuit, low power and high-speed nanoelectronic device applications.

Tunable negative differential resistance in planar graphene superlattice resonant tunneling diode

Here, we study the negative differential resistance (NDR) of Dirac electrons in biased planar graphene superlattice (PGSL) and investigate the transport characteristics by adopted transfer matrix method within Landauer-Buttiker formalism. Our model device is based on one-dimensional Kronig–Penney type electrostatic potential in monolayer graphene deposited on a substrate, where the bias voltage is applied by two electrodes in the left and right. At Low bias voltages, we found that NDR appears due to breaking of minibands to Wannier-Stark ladders (WSLs). At the critical bias voltage, delocalization appeared by WS states leads to tunneling peak current in current-voltage (I-V) characteristics. With increasing bias voltage, crossing of rungs from various WSL results in multi-peak NDR. The results demonstrate that the structure parameters like barrier/well thickness and barrier height have remarkable effect on I-V characteristics of PGSL. In addition, Dirac gap enhances peak to valley (PVR) value due to suppressing Klein tunneling. Our results show that the tunable PVR in PGSL resonant tunneling diode can be achievable by structure parameters engineering. NDR at ultra-low bias voltages, such as 100 mV, with giant PVR of 20 is obtained. In our device, the multiple same NDR peaks with ultra-low bias voltage provide promising prospect for multi-valued memories and the low power nanoelectronic tunneling devices.

Insight into negative differential resistance in polyphenylene molecular device with graphene electrodes

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.

A modified macro model approach for SPICE based simulation of single electron transistor

A new macro model of single electron transistor (SET) for SPICE based simulation of SET circuits is proposed. Two voltage controlled current sources and some scaling factors are incorporated in the existing model to derive our model. The V---I characteristics of the proposed SET is promising enough to be used as the basic element for designing circuits based on SETs. A comparison with the previous models establishes the fact that our model efficiently removes the drawbacks of the existing models. Our model also agrees well with the results obtained from popular SIMON simulator. To verify the accuracy, we have designed a SET inverter cell and investigated its characteristics. The work includes the effect of the parameters on the noise margin and voltage transfer characteristics of the inverter circuit. Further, to verify the applicability, a multi peak negative differential resistance circuit based on the proposed model is designed and simulated.

All-Graphene Planar Double-Quantum-Dot Resonant Tunneling Diodes

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 $10^{4}$ , 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.

A new SPICE macro model of single electron transistor for efficient simulation of single-electronics circuits

To explore single-electron circuits for different applications, a proper simulation platform where circuits consisting of single electron transistors and other devices can be simulated efficiently is needed. A macro model of single electron transistor featuring symmetric tunnel junctions is proposed. In the proposed model, a voltage controlled current source is incorporated in the existing model of SET to get more accurate results. Three scaling factors have been included in the model to improve the versatility of the model. The advantages and disadvantages of different simulation methods are discussed as a justification for choosing the macro model approach. The proposed model can efficiently describe the physical phenomena occurring in coulomb blockade and coulomb oscillation regions. The SPICE environment is used for the simulation and to verify the accuracy, the model is applied to a single electron inverter circuit and the effect of macro model parameters on the noise margin is investigated to estimate the robustness of the inverter cell. A multi peak negative differential resistance circuit based on the proposed macro model is designed and demonstrated. Also, an integrator circuit has been designed to prove the validity of the proposed model in the analog domain. Further, the linearity of the integrator circuit is analyzed through harmonic and intermodulation distortion analysis.

Multipeak negative differential resistance from interplay between nonlinear stark effect and double-branch current flow

Multipeak negative differential resistance (NDR) molecular devices are designed from first principles.

Negative Differential Resistance Arising from Tunneling Current through Multiple Quantum Dots

The tunneling current through multiple quantum dots (QDs) sandwiched between metallic contacts is theoretically studied in the framework of Green's function technique. The Anderson model with multiple energy levels is employed to simulate the considered system. We found that the negative differential resistance (NDR) arises from the interdot Coulomb interactions and the QDs under shell-filling conditions. Such NDRs are suppressed by the temperature effect. It is expected that multipeak NDR devices could be realized using a sophisticated layout of quantum dots.

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.

Multipeak negative-differential-resistance device by combining SET and MOSFET

A multipeak negative-differential-resistance(NDR) device which comprises a singl e-electron transistor (SET) and a metal-oxide-semiconductor field-effect-transis tor (MOSFET) can achieve infinite number of peaks in principle. The MOS device e liminates the large SD voltage dependence of the peak and volley currents of the SET. The multipeak NDR device can be widely used in multiple-valued logics, and analog-to-digital converters (ADCs). We obtain a multiple-valued memory unit th rough the multipeak NDR device. And by using the folding I-V characteristic, a four-bit ADC is achieved. Compared with the traditional flash ADC, the SET-MO SFET ADC is very simple.