Theoretical Studies of Electron Transport in Thiophene Dimer: Effects of Substituent Group and Heteroatom

Abstract

The electron-transport properties of various substituted molecules based on the thiol-ended thiophene dimer (2Th1DT) are investigated through density functional theory (DFT) combined with nonequilibrium Green's function (NEGF) method. The current-voltage (I-V) curves of all the Au/2Th1DT/Au systems in this work display similar steplike features, while their equilibrium conductances show a large difference and some of these I-V curves are asymmetric distinctly. The results reveal the dependence of conductance on the energy level of the substituted 2Th1DT molecules. Rectification ratios are computed to examine the asymmetric properties of the I-V curves. The rectifying behavior in the 2Th1DT molecule containing the amino group close to the molecular end is more prominent than that in the other molecules. The rectifying behavior is analyzed through transmission spectra and molecular projected self-consistent Hamiltonian (MPSH) states. Slight negative differential resistance (NDR) can be observed in some of the systems. The electron-transport properties of 2Th1DT molecules containing different heteroatoms are also investigated. The results indicate that the current in heteroatom-containing molecules is larger than that in their pristine analogues, and lighter heteroatoms are more favorable than heavier heteroatoms for electron transport of the thiophene dimer.

Theoretical Studies of the Spin-Dependent Electronic Transport Properties in Ethynyl-Terminated Ferrocene Molecular Junctions

“…The smaller molecule may be made into the smaller molecular junction with a more stable configuration, which is more meaningful for future application in nano-level circuits. Moreover, the electronic structures of the smaller molecules are usually easier to be influenced by chemical modification relative to the bigger molecules, thus the electronic transport properties are easier to be modified to achieve the required device function [ 38 ]. Therefore, for the ethynyl-terminated ferrocene molecules with different configurations, spin-dependent electron transport is worthwhile to be studied.…”

Large negative differential resistance and rectifying behaviors in isolated thiophene nanowire devices

“…From Figure 2(b), one can see that the current continually increases with the bias voltage, but the current rises slowly after ±1.54 V and follows a steep rise, which is in agreement with the available I-V curves. 15,18 This also provides a direct evidence of the reliability of the method used in this paper. These differences of the electronic transport through the same molecule junctions with two different electrode configurations can be understood easily by the transmission coefficient T(E) at zero bias and the density of states (DOS), which show the following characteristics: (1) The distinctive feature of the T(E) in Figure 2(c) is the existence of the narrow transmission peaks around the Fermi level, which determines an oscillatory I-V characteristic in 1D device shown in Figure 2(a).…”

“…Furthermore, it is notable that the I-V curves of both system A and B show several prominent NDR peaks. However, these large NDR and rectifying behaviors along with the oscillation effects were not found in previous experimental and theoretical works, [15][16][17][18][19] where the 3D gold electrodes were used to connect the 2T molecule. Thus, as a check, Figure 2(b) also displays the I-V curve of the same 2T molecule sandwiched between two 3D gold electrodes as depicted in Figure 1(b).…”

“…10,11 The experimental and theoretical studies of thiophene molecular junctions have been carried out by anchoring the thiophene molecule on electrode surfaces to probe the electronic transport properties. [12][13][14] More recently, theoretical simulations using ab initio quantum transport method have been successfully used to investigate the electronic transport behaviors of various single thiophene oligomers, including the effects of substituent group, 15 geometric structures, and moleculemetal contact properties etc. 16,17 However, besides these traditional factors, it is well known that the separation between the individual components should also be within the atomic or nanoscale regime in order to take advantage of the extreme miniaturization of molecular electronic devices.…”

Charge transport and transfer phenomena involving conjugated acenes and heteroacenes

“…SNn molecules could be anchored to Au-surface through various modes. The transport properties of molecular nanojunction strongly depend on the anchoring groups through which the molecules are connected with the electrodes [147]. For anchoring a molecule with metal surfaces, in general, thiols/thio-ethers, amines, carboxylic acids, sulphides, phosphides, etc.…”