Displacement Effects on the Electrical Characteristics of a Single-Molecule Device

The displacement of molecules is one of the major fabrication faults in manufacturing molecular electronic devices. In this paper, we profoundly study the effect of displacement on the current-voltage, and conductance-voltage characteristics of the Au-Benzenedithiol-Au single-molecule device. The ab-initio calculations on the isolated molecules were performed to obtain the basic single-level quantum-dot model parameters. These parameters were then used within the self-consistent field algorithm to calculate the electrical characteristics of the device. The maximum conductance occurs when the molecule is placed exactly in the midpoint of the distance between the two electrodes, where the electrostatic capacitance reaches its minimum. When the molecule deviates from this point, and approaches one electrode, the conductance is decreased, and asymmetric behavior emerges. A molecular rectifier can be manufactured by placing the molecule close to one electrode. Although modern software packages may employ advanced and complicated models including the combination of the density functional theory (DFT) and non-equilibrium Green’s function (NEGF) methods to obtain accurate results, they are demanding in computer memory and time. Moreover, understanding the physical quantities of the systems from large-scale matrices is often difficult. The single-level model is a computationally light method, which provides a profound understanding of the device characteristics since all quantities are presented by numbers.