苯環直接與鉑電極連接之電子輸運性質

Abstract

我們研究分子接面的電子傳輸性質與量子效應。以第一原理計算的方式，計算苯環分子直接與鉑電極連接的電子傳輸性質以及其量子效應，與傳統使用硫-金鍵結將苯環和金電極連接的方法比較，直接與鉑電極連接的系統可以得到較高的電導。我們改變偏壓以及電極間的距離，得到的電導約為0.20到0.85 G0，若將電極間的距離拉大，會影響電子的穿隧機率，導致電導下降。另外我們還研究了電子和聲子間的交互作用，觀察分子振動對inelastic current的影響，並找出所對應到的normal mode。最後我們計算此系統的量子干涉現象，2nd moment以及3rd moment shot noise。

Using first-principles approaches, we have investigated the electron transport properties of benzene molecules which directly connect between two Pt electrodes. Compared with the traditional benzene molecular junction where the molecule is connected to the electrodes via the Au-S covalent bond, direct connecting systems have much larger conductance ranging from 0.20 to 0.85 G0 for different bias and distance between two electrodes. When we increase the distance between Pt electrodes, it will decrease the transmission probability of electrons such that the conductance is reduced. We investigate the influence of different direct binding geometries, relevant to the normal mode energies, on the inelastic features. We also develop theory to calculate zero temperature quantum fluctuations of current including the shot noise and three cumulant for the benzene molecule with direct connection to electrodes.