共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
在第一性原理基础上,利用弹性散射格林函数方法,研究了六元杂环分子结2,5-哒嗪二硫酚 、2,5-吡嗪二硫酚和2,5-嘧啶二硫酚的电子输运特性,分析了终端原子的选取对杂环分子吡 啶电学特性的影响. 利用分子前线轨道理论和微扰方法定量地确定了分子与金属的相互作用 能参数. 计算结果表明,2,5-哒嗪二硫酚具有较好的电学特性,而2,5-嘧啶二硫酚在外加电 压较低时电导值比较小. 对于吡啶分子,选取硒原子作为终端原子时,其导电特性优于分别 以氧原子和硫原子作为终端原子的情况.
关键词:
六元杂环分子
伏安特性
电子输运
分子电子学 相似文献
3.
Molecular electronic devices that utilize single molecules or molecular monolayers as active electronic components represent a promising approach in the ongoing miniaturization and integration of electronic devices. Rapid advances in technology have enabled us to engineer molecular electronic devices with diverse functionalities. Significant progress has been made in understanding charge transport in molecular systems at the single-molecule level, and concomitantly, new device concepts have emerged. This review article focuses on experimental aspects of electronic devices made with single molecules or molecular monolayers, with a primary focus on the characterization and manipulation of charge transport. 相似文献
4.
M. Stopa Tsuyoshi Hatano Takeshi Ota Kazumasa Yamada Seigo Tarucha 《Superlattices and Microstructures》2003,34(3-6):439
We develop a model for transport through benzene-based single molecules with an NO2 side-group, which incorporates bond bending between the NO2 and the adjacent benzene ring and successfully reproduces the experimentally observed strong negative differential resistance. Transport through the molecule is assumed to be incoherent and is treated using photon assisted tunnelling. 相似文献
5.
H. Aghaie M.R. Gholami M. Monajjemi M.D. Ganji 《Physica E: Low-dimensional Systems and Nanostructures》2008,40(9):2965-2972
The electron transport characteristics of a 1,10-dimethylene-1,10-dicarba-closo-decaborane (10-vertex carborane) single molecular conductor is investigated via the density functional-based non-equilibrium Green's function (DFT-NEGF) method. We consider three configurations for the molecular wire sandwiched between two Au(1 0 0) electrodes: the hollow site, top site and bridge site positions. Our results show that the energetically favorable hollow site configuration has a higher current intensity than the other configurations.The projection of the density of states (PDOS) and the transmission coefficients T(E) of the two-probe system at zero bias are analyzed, and it suggests that the variation of the coupling between the molecule and the electrodes with external bias leads to the higher conductance for the hollow configuration.Furthermore, the transmission coefficients of the hollow system at various external voltage biases are also investigated and it shows that the broadening of the transmission coefficient spectrum with increasing of the external voltage bias indicates a strong coupling between the molecular orbitals in the carborane and the incident states from the electrodes, and thus the current increases with increases of the bias voltage. 相似文献
6.
Jinhuan Yao Yanwei Li Zhengguang ZouJianwen Yang Zhoulan Yin 《Physica B: Condensed Matter》2011,406(20):3969-3974
The electron transport properties of cis-polyacetylene and cis-polyacetylene based molecular wires (oligo(cyclopentadiene), oligo(pyrrole), and oligo(furan)) have been studied theoretically using a combination of density-functional theory and non-equilibrium Green′s functions method. The results demonstrate that the introduction of bridging group X (X=CH2, NH, and O) in cis-polyacetylene has a profound effect on the electron transport behavior of the molecules. The conductance of the four molecular wires decreases in the order of polyacetylene>oligo(cyclopentadiene)>oligo(furan)>oligo(pyrrole). In particular, the conductances of oligo(furan) and oligo(pyrrole) are much lower than those of polyacetylene and oligo(cyclopentadiene). The mechanism of this difference of electron transport properties of these four molecular systems is analyzed in terms of their geometric structures, electronic structures, transmission spectra, and spatial distribution of frontier orbitals. It is found that the energy levels of frontier molecular orbitals and the evolution of spatial distribution of frontier molecular orbitals with the applied bias are the essential reason for generating this difference of electron transport behaviors of the four molecular systems. 相似文献
7.
Kamil Walczak 《Central European Journal of Physics》2006,4(3):349-362
Here we present the calculations of incoherent current flowing through the two-site molecular device as well as the DNA-based
junction within the rate-equation approach. Selected phenomena of interest are discussed in detail. The structural asymmetry
of a two-site molecule results in a rectification effect, which can be neutralized by an asymmetric voltage drop at the molecule-metal
contacts due to coupling asymmetry. The results received for the poly(dG)-poly(dC) DNA molecule reveal the coupling-and temperature-independent
saturation effect of the current at high voltages, establishing for short chains the inverse square distance dependence. Additionally
we document the conductance peak shifting in the direction of higher voltages due to a temperature decrease. 相似文献
8.
Non-equilibrium Green's functions (NEGF) formalism combined with extended Hückel (EHT) and charging model are used to study
electrical conduction through single-molecule junctions. The analyzed molecular complex is composed of the asymmetric 1,4-Bis((2′-para-mercaptophenyl)-ethinyl)-2-acetyl-amino-5-nitrobenzene molecule symmetrically coupled to two gold electrodes. Owing to this
model, the accurate values of the current flowing through such junctions can be obtained by utilizing basic fundamentals and
coherently deriving model parameters. Furthermore, the influence of the charging effect on the transport characteristics is
emphasized. In particular, charging-induced reduction of conductance gap, charging-induced rectification effect and charging-generated
negative value of the second derivative of the current with respect to voltage are observed and examined for the molecular
complex. 相似文献
9.
Using the RTM/NEGF method, which is a first-principles calculation tool for the quantum transport through nanostructures between electrodes, we study the effects of atomic-scale contacts on the transport properties through single molecules. Electronic states and current-voltage (I-V) characteristics are investigated in various contact conditions with and without single molecules between electrodes. We find that similar nonlinear behaviors appear in the I-V characteristics. Such nonlinear behaviors are determined not only by the HOMO-LUMO electronic states of single molecules between electrodes, but also by the atomic-scale contact conditions. We show that the transitions from tunneling to ballistic regimes affect the I-V characteristics significantly. 相似文献
10.
The quantum transport properties of a non-interacting mesoscopic ring sandwiched between two metallic electrodes are investigated by the use of Green's function technique. Here, we introduce parametric approach, based on the tight-binding model to study these transport properties. The electronic transport properties are focused in three aspects: (a) geometry of the mesoscopic ring, (b) coupling strength of the ring with the two electrodes and (c) magnetic flux threaded by the ring. 相似文献
11.
We investigate quantum mechanical electron transport along the long axis of the DNA molecule using an effective tight-binding model. The overall contour plot of transmission, the current-voltage characteristics, and the differential conductance are examined for the variation of backbone onsite energy, the energy-dependent hopping strength, and the contact coupling between the leads and the DNA molecule. It is shown that as backbone asymmetry increases, the merging and collapse of the two mini-bands take place and an extra resonance peak in the transmission appears. In addition, we present the modulation of voltage threshold in the current-voltage curves and a double-peak structure in the differential conductance due to the disappearance of the merged mini-band. Finally, in the Coulomb blockade regime of asymmetric contact coupling, a distinct and under-unity resonance in the transmission appears due to the interference effects between the DNA molecular bands and the electronic structure of the leads at the DNA-lead interface. 相似文献
12.
T. Brandes 《Annalen der Physik》2008,17(7):477-496
The waiting time distribution w(τ), i.e. the probability for a delay τ between two subsequent transition (‘jumps’) of particles, is a statistical tool in (quantum) transport. Using generalized Master equations for systems coupled to external particle reservoirs, one can establish relations between w(τ) and other statistical transport quantities such as the noise spectrum and the Full Counting Statistics. It turns out that w(τ) usually contains additional information on system parameters and properties such as quantum coherence, the number of internal states, or the entropy of the current channels that participate in transport. 相似文献
13.
The effect of molecular orientation on the electron transport behavior of single porphyrin sandwiched between two gold (111) electrodes is investigated by density functional theory calculations combined with non-equilibrium Green’s function method. The results show that the porphyrin with parallel connection to gold (111) electrodes is more conductive than the porphyrin with diagonal connection to gold (111) electrodes. The mechanism of the difference of electron transport for these two molecular junctions is analyzed from the transmission spectra and the molecular projected self-consistent Hamiltonian states. It is found that the intrinsic nature of the molecule, such as the π-conjugated framework and the strength of molecule–electrode coupling, are the essential reason for generating this difference of electron transport for the two molecular systems. 相似文献
14.
We extend the Green function approach to quantum transport through an anisotropic molecular magnet system with the help of Hubbard operators. Based on the single molecular magnet model, we reformulate the large spin and the total Hamiltonian in the language of Hubbard operators and obtain analytical expressions of the retarded Green function in sequential tunneling and Kondo regimes. In addition to this, we show the connection of our method to the master equation method in sequential regime and discuss a simple isotropic case in Kondo regime, in which we find a three-peak Kondo structure, a feature characterizing the isotropic exchange interaction between the localized electron and large spin. 相似文献
15.
A.R. Saha C.B.- Dimitriu S. Chattopadhyay A.G. O’Neill 《Applied Surface Science》2006,252(11):3933-3937
Based on Quantum Mechanical (QM) carrier transport and the effects of interface states, a theoretical model has been developed to predict the anomalous current-voltage (I-V) characteristics of a non-ideal Ni-silicided Schottky diode at low temperatures. Physical parameters such as barrier height, ideality factor, series resistance and effective Richardson constant of a silicided Schottky diode were extracted from forward I-V characteristics and are subsequently used for the simulation of both forward and reverse I-V characteristics using a QM transport model in which the effects of interface state and bias dependent barrier reduction are incorporated. The present analysis indicates that the effects of barrier inhomogeneity caused by incomplete silicide formation at the junction and the interface states may change the conventional current transport process, leading to anomalous forward and reverse I-V characteristics for the Ni-silicided Schottky diode. 相似文献
16.
Florian Pump Ruslan Temirov Olga Neucheva Serguei Soubatch Stefan Tautz Michael Rohlfing Gianaurelio Cuniberti 《Applied Physics A: Materials Science & Processing》2008,93(2):335-343
Using a scanning tunneling microscope we have measured the quantum conductance through a PTCDA molecule for different configurations
of the tip–molecule–surface junction. A peculiar conductance resonance arises at the Fermi level for certain tip to surface
distances. We have relaxed the molecular junction coordinates and calculated transport by means of the Landauer/Keldysh approach.
The zero bias transmission calculated for fixed tip positions in lateral dimensions but different tip–substrate distances
show a clear shift and sharpening of the molecular chemisorption level on increasing the STM–surface distance, in agreement
with experiment. 相似文献
17.
Shingo Katsumoto Masahiro Sato Hisashi Aikawa Yasuhiro Iye 《Physica E: Low-dimensional Systems and Nanostructures》2006,34(1-2):36
The effect of localized spins on the quantum coherence in solids is discussed. A quantum dot with an odd number of electrons can be a model system for a localized spin. It is experimentally shown that a spin flip scattering by a quantum dot pulls the trigger of quantum decoherence. On the other hand, spin flip scattering is the basic process to construct the Kondo singlet state around a magnetic impurity. Through an interference effect of the Kondo state (the Fano–Kondo effect) in a side-coupled dot system, we show experimentally that the Kondo singlet state is quantum mechanically coherent. The analysis of the Fano–Kondo lineshape indicates the locking of the phase shift to π/2, which is in agreement with theoretical predictions. The Fano–Kondo effect is also observed in an Aharonov–Bohm ring, in which a quantum dot is embedded, and also indicates the phase shift locking to π/2. 相似文献
18.
Jinhuan Yao Yanwei Li Zhengguang Zou Hongbo Wang Yufang Shen 《Superlattices and Microstructures》2012
The nonequilibrium Green’s function approach in combination with density-functional theory is used to perform ab initio quantum-mechanical calculations of the electron transport properties of polyacetylene, polythiophene, poly(phenylene vinylene), poly(p-phenylene ethynylene), and poly(p-phenylene) molecules sandwiched between two gold electrodes. The results demonstrate that the conjugation path has a profound effect on the electron transport property of the molecular wires. Among the five molecular wires, polyacetylene is the most conductive one. The conductivities of the five molecular wires decrease with an order of polyacetylene > polythiophene > poly(phenylene vinylene) > poly(p-phenylene ethynylene) > poly(p-phenylene). The conductivities of polyacetylene and polythiophene are much higher than those of poly(phenylene vinylene), poly(p-phenylene ethynylene), and poly(p-phenylene). The difference of electron transport behaviors of these molecular wires are analyzed in terms of the electronic structures, the transmission spectra, and the spatial distributions of molecular orbitals. 相似文献
19.
Kamil Walczak 《Central European Journal of Physics》2006,4(2):241-253
In this work we study the effect of decoherence on elastic and polaronic transport via discrete quantum states. Calculations
are performed with the help of a nonperturbative computational scheme, based on Green’s function theory within the framework
of polaron transformation (GFT-PT), where the many-body electron-phonon interaction problem is mapped exactly into a single-electron
multi-channel scattering problem. In particular, the influence of dephasing and relaxation processes on the shape of the electrical
current and shot noise curves is discussed in detail under linear and nonlinear transport conditions. 相似文献
20.
G. -Q. Hai N. Studart G. E. Marques F. M. Peeters P. M. Koenraad 《Physica E: Low-dimensional Systems and Nanostructures》1998,2(1-4)
The multisubband electron transport properties are studied for doped single quantum well and gated double asymmetric quantum well structures. The effects due to intersubband interaction and screening of the ionized impurity scattering are also investigated. We show that intersubband coupling plays an essential role in describing the screening properties as well as the effect of ionized impurity scattering on the mobility in a doped single quantum well. For coupled double quantum well structures, negative transconductance is found theoretically which is due to resonant tunneling between the two quantum wells. 相似文献