Au-Si_6-Au纳米结点电子输运行为的理论计算

Theoretical calculation of electron transport behavior of Au-Si_6-Au nanoscale junctions

运用密度泛函理论结合非平衡格林函数的方法,对Si6原子链与两半无限Au（100）-3×3电极耦合构成纳米结点的电子输运行为进行了理论模拟,对结点在不同距离下的电导、结合能进行了计算,结果得到当两电极距离为2.219nm时,结点结合能较大,结构比较稳定,此时Si-Si平均键长为0.213nm,Si-Au键长为0.228nm.对于稳定结构结点,平衡电导为1.093G0,电子主要通过Si原子的px与py态电子形成的π键进行传输;在-1.2-1.2V的电压范围内,Si原子链导体具有比较稳定的电导,表现出类似金属的导电特性,其I-V曲线近似为直线关系.

Electron transport behavior of Au-Si6 -Au nanoscale junctions, which consists of six silicon atoms sandwiched between two semi--infinite Au（100）--3 × 3 electrodes, were investigated with combination of density functional theory and the non-equilibrium green＇s function method from first principles. We calculated conductance and the binding energy in different distance. The results show that the binding energy of junctions is near to maximum and the structure is stable when dz= 2. 219 nm. The corresponding average length of St-St and Si-Au bond is 0. 213 nm and 0. 228 nm, respectively. Besised, the equilibrium conductance is 1. 093G0. The electrons transmit mainly through the tunneling channel of bonds formed by px and Py orbital electrons of Si atoms. In voltage range from -1.2 to 1.2 V, silicon atomic chain conductor has a stable electron transport behavior, and the I-V curve of the junctions show approximate linear feature similar to the metal conductor.