Transition from Tunneling to Hopping in Single Molecular Junctions by Measuring Length and Temperature Dependence
Transition from Tunneling to Hopping in Single Molecular Junctions by Measuring Length and Temperature Dependence
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通过测量长度和温度依赖性从单分子结中的隧道过渡到跳跃
DOI：
10.1021/ja1040946
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发表时间：
2010-08-25
影响因子：
15
通讯作者：
Tao, Nongjian
中科院分区：
文献类型：
--
作者：
Hines, Thomas;Diez-Perez, Ismael;Tao, Nongjian
利用扫描隧道显微镜破结技术研究了一类长共轭分子线的电荷输运特性。该系列由4条线组成，长度从3.1到9.4纳米不等。两根较短的导线表现出高度依赖长度和温度不变的电导行为，而较长的导线表现出弱依赖长度和温度变化的电导行为。这种趋势与一种模型是一致的，即在金属丝家族中，传导是通过两种不同的机制发生的：在较短的两种金属丝中，传导是通过相干隧道机制发生的，而在较长的金属丝中，传导是通过非相干电荷跳变过程发生的。两种传导机制的温度依赖性产生了一种现象，即在高温下，通过电荷跳变传导的较长分子比通过隧道传导的较短导线产生更高的电导率。在单个瞬态电流衰减曲线特征的背景下，研究并解释了分子结在尖端收缩时的演变。
The charge transport characteristics of a family of long conjugated molecular wires have been studied using the scanning tunneling microscope break junction technique. The family consists of four wires ranging from 3.1 to 9.4 nm in length. The two shortest wires show highly length dependent and temperature invariant conductance behavior, whereas the longer two wires show weakly length dependent and temperature variant behavior. This trend is consistent with a model whereby conduction occurs by two different mechanisms in the family of wires: by a coherent tunneling mechanism in the shorter two and by an incoherent charge hopping process in the longer wires. The temperature dependence of the two conduction mechanisms gives rise to a phenomenon whereby at elevated temperatures longer molecules that conduct via charge hopping can yield a higher conductance than shorter wires that conduct via tunneling. The evolution of molecular junctions as the tip retracts has been studied and explained in context of the characteristics of individual transient current decay curves.