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Organic molecular field‐effect transistors (FETs) are promising building components for future electronic circuits. Efficient control of charge transport properties is one key issue in the design of organic molecular FETs. In this study, we propose a redesign of a naphthalene‐based FET by introducing two azulene components in opposite dipole moment directions. Using density functional theory combined with non‐equilibrium Green's function, the simulated electronic transport characteristics reveal that the introduction of polar azulene components effectively narrows the frontier molecular orbitals gap, leading to an increase in the ON‐state current. Meanwhile, the OFF‐state current is significantly suppressed by highly localizing the dominant electronic transport channel. As a result, improved gate controllability is achieved with a higher ON‐OFF current ratio, which is nearly seven times higher than that of the naphthalene‐based FET device. These findings provide theoretical directions for future design of organic molecular FET devices with enhanced gating regulation efficiency. [ABSTRACT FROM AUTHOR]

With the development of device miniaturization, traditional Si‐based field effect transistors (FETs) are approaching their scaling limits. It is necessary to find more alternative materials to improve the performance of FETs. 2D semiconductors attract great attention for channel material due to their atomic‐scale smoothness and dangling‐bond‐free surface, and the gate electrostatic properties and charge carrier mobility are better than traditional 3D Si‐based semiconductor. In this paper, using density functional theory combined with nonequilibrium Green's function formalism, the electronic properties and device performance of sub‐5 nm monolayer SiMe‐graphene n‐type field‐effect transistors are evaluated. Remarkably, the on‐state current value of the FET can reach 3070 µA µm−1, which greatly surpasses most of reported FETs based on other 2D semiconductors. In addition, the on‐state current, power dissipation, and delay time of the SiMe‐graphene FETs satisfy the high‐performance requirements of the 2020 International Roadmap for Device and Systems under different supply voltages, which indicates that the FETs can work at different operating frequencies and power consumption. Moreover, via controlling electrode doping concentration, the channel length can be reduced to 4 nm. In total, the SiMe‐graphene is a favorable channel material for future FETs devices. [ABSTRACT FROM AUTHOR]

By using nonequilibrium Green's function in combination with density functional theory, we study the electronic transport properties of two typical π-conjugated molecules (dithiol-benzene and C4S2), sandwiched between two metallic electrodes made of different metals. The presence of two different electrodes leads to Fano resonances at certain energy. As a consequence, electronic transport in future molecular electric circuits can be substantially affected when the molecular devices placed between electrodes with different chemical potentials. The Fano line shapes reveal that there is nonresonant channel when two asymmetric electrodes are employed. [ABSTRACT FROM AUTHOR]

Abstract: We report first-principles calculations of the current-voltage characteristic and the conductance of carbon-based molecular wires with different length capped with sulfur ends between two metallic electrodes made of different metals. The optimized molecular structure of carbon chain in the junction is presented on the structure of polyyne. The conductance of the polyyne wires shows oscillatory behavior depending on the number of carbon atoms (triple bonds). Current rectification is found and rectification direction presents inversion with the odd and even number of carbon atoms. [Copyright &y& Elsevier]

Abstract: By applying non-equilibrium Greenʼs functions in combination with the density-functional theory, we investigate the transport behavior of molecular devices composed by metal electrode–C60 molecule–metal electrode. Our results show that the electronic transport properties are affected obviously by the different contact distances between the electrodes, and the tunneling current decreases approximately exponentially at a certain bias with the increasing of contact distances. The negative differential resistance is observed and the peak-to-valley ratio can be tuned by different contact distances. The mechanisms of the contact distance effect and the negative differential resistance behavior are proposed. [Copyright &y& Elsevier]