Charge transport at a molecular GaAs nanoscale junction.
Charge transport at a molecular GaAs nanoscale junction.
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DOI：
10.1039/c8fd00016f
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发表时间：
2018-10
影响因子：
3.4
通讯作者：
A. Vezzoli;Richard J Brooke;Nicoló Ferri;Carly Brooke;S. Higgins;W. Schwarzacher;R. Nichols
中科院分区：
文献类型：
--
作者：
A. Vezzoli;Richard J Brooke;Nicoló Ferri;Carly Brooke;S. Higgins;W. Schwarzacher;R. Nichols
近年来，使用非金属电极制造单分子结已经发展成为一种赋予纳米器件新特性的优雅方式。在半导体平台中集成分子结也将加快技术部署，因为它将利用现有的工业基础设施。在之前的概念验证论文中，我们使用砷化镓（GaAs）衬底上的简单α，ω-二硫醇自组装单层来制造STM分子肖特基二极管。在设备中，我们还能够检测到单个分子对整体电荷传输的贡献。所制备的器件也可以用作光电二极管，因为GaAs是III-V直接带隙（室温下为1.42 eV）半导体，并且它有效地吸收可见光以产生光电流。在这方面的贡献，我们表明，精细控制可以施加在一个金属分子GaAs结的电行为，通过系统地改变分子桥的性质，半导体的类型和掺杂密度和光的强度和波长。分子轨道能量排列主导的电荷传输特性，导致在强整流结制备的饱和桥（如烷二硫醇），越来越多的欧姆特性的饱和度降低，通过引入共轭部分。我们观察到的效应是局部的，可以用几十纳米大小的电极观察到，因此为使用半导体纳米电极探测分子特性铺平了道路。最后对单分子半导体电化学的发展前景进行了展望。
In recent years, the use of non-metallic electrodes for the fabrication of single-molecule junctions has developed into an elegant way to impart new properties to nanodevices. Integration of molecular junctions in a semiconducting platform would also speed technological deployment, as it would take advantage of established industrial infrastructures. In a previous proof-of-concept paper, we used simple α,ω-dithiol self-assembled monolayers on a gallium arsenide (GaAs) substrate to fabricate molecular Schottky diodes with a STM. In the devices, we were also able to detect the contribution of a single-molecule to the overall charge transport. The prepared devices can also be used as photodiodes, as GaAs is a III-V direct bandgap (1.42 eV at room temperature) semiconductor, and it efficiently absorbs visible light to generate a photocurrent. In this contribution, we demonstrate that fine control can be exerted on the electrical behaviour of a metal-molecule-GaAs junction by systematically altering the nature of the molecular bridge, the type and doping density of the semiconductor and the light intensity and wavelength. Molecular orbital energy alignment dominates the charge transport properties, resulting in strongly rectifying junctions prepared with saturated bridges (e.g. alkanedithiols), with increasingly ohmic characteristics as the degree of saturation is reduced through the introduction of conjugated moieties. The effects we observed are local, and may be observed with electrodes of only a few tens of nanometres in size, hence paving the way to the use of semiconducting nanoelectrodes to probe molecular properties. Perspectives of these new developments for single molecule semiconductor electrochemistry are also discussed.