Kondo Hisashi, Nara Jun, Kino Hiori, Ohno Takahisa
CMSC, National Institute for Materials Science (NIMS), Tsukuba, Ibaraki 305-0047, Japan. Institute of Industrial Science, University of Tokyo, Meguro, Tokyo 153-8505, Japan.
J Phys Condens Matter. 2009 Feb 11;21(6):064220. doi: 10.1088/0953-8984/21/6/064220. Epub 2009 Jan 20.
We investigate the transport properties of a biphenyl-dithiol molecule sandwiched between electrodes made of metal Y (Y = Cu, Ag and Au) using the non-equilibrium Green's function method based on a density functional theory. The electrode metal Y has an influence on the coupling between the molecule and electrodes, and thus on the transmission peak height. For the transmission T(Y) at the Fermi energy, we obtain T(Cu)∼T(Ag)<T(Au). As a result, the current value at low bias voltage for the junction system with Ag or Cu electrodes is smaller than that for Y = Au. At high bias voltage, on the other hand, the current value of an Ag electrode system becomes larger than the others due to the higher transmission peak around -1.5 eV below the Fermi energy. Besides this, it is shown that the transmission peak value for all the electrode metals can be expressed generally as a function of a ratio of the coupling between the two phenyl rings to the peak width of the projected density of states with respect to a corresponding molecular orbital.
我们基于密度泛函理论，使用非平衡格林函数方法研究了夹在由金属Y（Y = 铜、银和金）制成的电极之间的联苯二硫醇分子的输运性质。电极金属Y对分子与电极之间的耦合有影响，进而对传输峰高度有影响。对于费米能处的传输系数T(Y)，我们得到T(铜) ∼ T(银) < T(金)。因此，具有银或铜电极的结系统在低偏置电压下的电流值小于Y = 金时的电流值。另一方面，在高偏置电压下，由于在费米能以下约 -1.5 eV处有较高的传输峰，银电极系统的电流值变得比其他系统大。除此之外，结果表明，所有电极金属的传输峰值通常都可以表示为两个苯环之间的耦合与相对于相应分子轨道的投影态密度峰宽之比的函数。
