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在两金电极间置于空间对称的苯硫(PDT)分子构成一分子器件模型,并通过移动其中一电极变对称接触为非对称接触.利用第一原理方法研究了该器件的输运性质,结果表明,器件的I(G)-V特性相对偏压极性有显著的非对称,其电流及电导的大小明显地依赖于分子与电极的接触距离,即非对称接触能导致器件伏安特性的弱整流效应.分析表明最高占据分子轨道(HOMO)是器件的共振隧穿轨道,偏压作用使器件充电进而移动HOMO是I(G)-V非对称性的内在原因.
A symmetric PDT molecule was placed between the two gold electrodes to form a molecular device model, and the asymmetric contact was changed by moving one of the electrodes. The first principle method was used to study the transport properties of the device. The results show that the I (G) -V characteristic of the device is significantly asymmetric with respect to the bias voltage. The magnitude of current and conductance obviously depends on the contact distance between the molecule and the electrode. That is, the asymmetric contact can lead to the device’s voltammetric characteristics (HOMO) is the resonant tunneling orbital of the device. The biasing effect of the device charging and moving HOMO is the intrinsic reason of I (G) -V asymmetry.