关键词: 非平衡格林函数, 分子器件, 量子输运, 密度泛函理论

Abstract:

Quantum transport properties of molecular devices are mostly measured by scanning tunneling microscopy (STM). The results show abnormal features such as asymmetric I-V (AIV) curve or negative differential conductance (NDC), which are not to be observed in the case of common macroscopic devices. Based on finite element method and parameter models, the Hamiltonian of a sample system with a local state is presented. The non-equilibrium Green's function method is used to calculate the electron density and the tunneling current of the device after self-consistent convergence. After investigating the effects of different parameters, including the electrode coupling strength, molecular energy level, local energy level, the influences of the local states and geometrical asymmetry on the transport properties of molecular devices have been analyzed. It is concluded that the intrinsic region of AIV and NDC in STM related molecular devices experiments is the offset of the local states in the tip.

Key words: non-equilibrium Green's function, molecular device, quantum transport, density functional theory