Zhang Z, Yang Z, Yuan J, Qiu M
School of Physics and Electronic Science, Changsha University of Science and Technology, Changsha 410076, The People's Republic of China.
J Chem Phys. 2008 Jan 28;128(4):044711. doi: 10.1063/1.2814247.
The properties of electronic transport in an electronic device composed of a spatially symmetric phenyldithiolate molecule sandwiched between two gold electrodes with asymmetric contact are investigated by the first-principles study. It is found that the I-V and G-V characteristics of a device show significant asymmetry and the magnitudes of current and conductance depend remarkably on the variation of molecule-metal distance at one of the two contacts. Namely, an asymmetric contact would lead to the weak rectifying effects on the current-voltage characteristics of a molecular device. We also calculate self-consistently other microscopic quantities such as the local density of states, the total density of states, and the distribution of charges in the asymmetric molecular models under the applied bias. The results show that the highest-occupied molecular orbital (HOMO) is responsible for the resonant tunneling and the shifting of the HOMO due to the charging of the device under the bias voltage is the intrinsic origin of asymmetric I(G)-V characteristics.
通过第一性原理研究，对由夹在两个具有不对称接触的金电极之间的空间对称苯基二硫醇盐分子组成的电子器件中的电子输运性质进行了研究。发现器件的I-V和G-V特性表现出显著的不对称性，并且电流和电导的大小显著取决于两个接触点之一处分子-金属距离的变化。也就是说，不对称接触会导致对分子器件电流-电压特性的弱整流效应。我们还自洽地计算了其他微观量，如局域态密度、总态密度以及在施加偏压下不对称分子模型中的电荷分布。结果表明，最高占据分子轨道（HOMO）负责共振隧穿，并且由于偏压下器件充电导致的HOMO的移动是不对称I（G）-V特性的内在起源。
