Interface trap-induced negative differential resistance in nMOSFET with floating source

Interface trap can act as the generation center in device to induce a very weak generation current. We observed the negative differential resistance NDR of this generation current I_D in nMOSFET with the floating source. It originates from that the generation function of interface trap is enabled and then is shut down in turn as increasing the drain voltage. This change relies on the interaction among the interface trap energy-level and the electron's Fermi-levels of drain and source under the floating source condition. It is found that the peak-to-valley ratio of I_D is beyond 30.     

Electronic transport properties in benzene-based heterostructure: Effects of anchoring groups

Using density functional theory (DFT) combined with nonequilibrium Green?s functions (NEGF), the electronic transport properties of benzene-based heterostructure molecular devices have been investigated. We focus on the contact geometry between molecules and electrodes, and several different anchoring groups have been considered. The current–voltage characteristics were calculated for positive and negative bias voltages, and discussed in terms of transmission spectra, transferred charges, and molecular projected self-consistent Hamiltonian (MPSH) states. Our results show that the anchoring groups play a crucial role in determining the overall conductivity of the molecular devices. Negative differential resistance (NDR) and rectifying effect can be observed.     

Investigation of negative differential resistance properties of self-assembled dipyridinium using STM

Recently, research on conducting molecules containing thiol functional groups such as benzenethiol has been progressing [X. Xiao, B. Xu, N.J. Tao, Nano Lett. 4 (2004) 267]. This conducting molecule is applicable to the study of the negative differential resistance (NDR) and switching properties of logic device. The 4-{4[4-(4-{1-[4-(4-acetylsulfanyl-phenylethynyl)-phenyl]-2,6-diphenyl-pyridinium-4-yl}-phenyl)-2,6-diphenyl-pyridinium-1-yl]-phenylethynyl}-phenylthioacetate (dipyridinium) molecule contains thiol functional groups such as benzenethiol. Thus, we have studied an NDR property of a dipyridinium molecule using the self-assembly method in scanning tunneling microscopy (STM). The Au substrate was exposed to a 1 mM solution of 1-dodecanethiol in ethanol for 24 h to form a monolayer. After thorough rinsing of the sample, it was exposed to a 0.1 μM solution of dipyridinium in dimethylformamide (DMF) for 30 min. After the assembly, we measured the electrical properties of the self-assembly monolayers (SAMs) using ultra high vacuum scanning tunneling microscopy (UHV-STM) and scanning tunneling spectroscopy (STS). As a result, we confirmed the properties of NDR in a negative region at −1.67 V and a positive region at 1.78 V. The energy gap (E_g) was found to be 3.12 eV [C. Arena, B. Kleinsorge, J. Robertson, W.I. Milne, M.E. Welland, J. Appl. Phys. 85 (1999) 1609]. This molecule is applicable to the fabrication of molecular junctions.     

Electrical instability in a semiconductor gas discharge system

Electrical instability in a SI GaAs plates of the semiconductor gas discharge gap system (SGDGS) is studied experimentally in a wide range of the gas pressures, interelectrode distances and different diameters of the cathode areas. While being driven with a stationary voltage, it generates current and discharge light emission (DLE) instabilities with different amplitudes of the oscillation. It is shown that under the experimental conditions the interelectrode distance played only a passive role and was not responsible for the appearance of the DLE instability. At the same time for different diameters D of the GaAs plate areas the expanded range of current and DLE oscillations are observed. SGDGS with an N‐shaped CVC was analyzed using both the current and DLE data showing the electrical instability in the GaAs cathode. It was found that application of high feeding voltage to this cathode give rise to non‐uniform spatial distribution of the DLE, which disturbed the operation of the system. The experiment presents also a new metod to study and visualization of the electrical instabilities in high‐resistivity GaAs plates of large diameter. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Magnetic field control of current through model graphene nanosheets

We study magnetic field control of current through model graphene nanosheet junctions within the framework of the tight-binding approximation. Geometrical asymmetry in the coupling of graphene nanosheets to the contact leads emerges as one of the most important determining factors for the magnetic field control of current. The asymmetric connection split the otherwise degenerate energy levels of the structures leading to energy-resolved transmission peaks which the applied field modulates for a transmission maximum by narrowing the energy gap between the split energy levels. Also, the contact coupling strength plays a decisive role in controlling current in small structures, while its role is significantly less in large structures that have more closely-spaced energy levels. Model calculations on a graphene nanosheet junction with inter-site Coulomb interaction is found to sustain sensitivity to the applied magnetic field. Although several factors bear direct effect on the electron transport through molecular junctions, suitably constructed graphene nanosheet junctions would greatly enhance the prospects of current control under applied magnetic fields.     

Current controlled negative differential resistance behavior in Co2FeO2BO3 and Fe3O2BO3 single crystals

I–V curves showing negative differential resistance (NDR) are reported for single crystals of Co₂FeO₂BO₃ at 315 K and 290 K and for Fe₃O₂BO₃ at 300 K, 260 K and 220 K. Resistivity measurements are presented for both systems, parallel and perpendicular to the c axis, in the range 315–120 K. The high hysteretic behavior of the I–V curves in Co₂FeO₂BO₃ around room temperature is discussed and the heat dissipated is estimated, suggesting an increase in the sample temperature of almost 22 K for the I–V curve at 315 K and a dominant contribution of Joule self-heating for the observed NDR. In contrast, insignificant hysteresis is observed on the I–V curves of Fe₃O₂BO₃ around room temperature. The depinning of charge order domains is suggested as the main contribution to the NDR phenomenon for Fe₃O₂BO₃. The high reproducibility of the NDR in the Fe₃O₂BO₃ single crystal allows its use as a low frequency oscillator, as it is demonstrated.     

Electronic transport for pristine and doped crossed graphene nanoribbon junctions with zigzag interfaces

Using the fully self-consistent non-equilibrium Green?s function (NEGF) method combined with density functional theory, we investigate numerically the electronic transport property for pristine and doped crossed graphene nanoribbon (GNR) junctions. It is demonstrated that in the case of zigzag interfaces, the I–V characteristics of the junction with or without doping always show semiconducting behavior, which is different from that in the case of armchair interfaces [Zhou, Liao, Zhou, Chen, Zhou, Eur. Phys. J. B 76 (2010) 421]. Interestingly, negative differential resistance (NDR) behavior can be clearly observed in a certain bias region for nitrogen-doped shoulder crossed junction. A mechanism for the NDR behavior is suggested.     

有机电双稳态器件

有机电双稳态器件(organic electrical bistability devices,OEBDs)具有低成本、易加工、小体积、快响应、低功耗和高存储密度等优点,在未来的信息存储和逻辑电路方面有着非常广阔的应用前景,正受到人们越来越多地的关注。但是有机电双稳态器件的工作原理还没有得到很好地理解,并且工作过程中所涉及的新概念、新理论等基本科学问题以及制备和加工过程中所涉及的新结构、新方法、新技术和新材料还有待进行深入地研究。本文综述了有机电双稳态器件近年来的研究进展,并探讨了它在电开关存储方面的应用前景以及需要解决的问题。     

DFT-NEGF study of transport properties and NDR behavior in fused furan and thiophene dimmers

The nonequilibrium Green's function approach in combination with density-functional theory is used to perform quantum mechanical calculations of the electron transport properties of furan and thiophene dimmers. Both the molecular systems have two S-linker and translated into the Gold junction with (1 1 1) surfaces. The studied molecular junctions at zero bias voltage are HOMO-based junctions and currents through these systems are driven by hole transport. The current–voltage characteristics of the both studied molecular junctions illustrate that negative differential resistance (NDR) feature is observed over the bias voltage of 2.0 V. Higher conductivity of fused furan dimmer and NDR character have been explained by the monitoring of the transmission resonance peak across the bias window against varying bias voltages.