Charge-state assignment of nanoscale single-electron transistors from their current-voltage characteristics
Charge-state assignment of nanoscale single-electron transistors from their current-voltage characteristics
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DOI：
10.1039/c9nr03754c
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发表时间：
2019-08-21
期刊：
影响因子：
6.7
通讯作者：
Anderson, Harry L.
中科院分区：
文献类型：
--
作者：
Limburg, Bart;Thomas, James O.;Anderson, Harry L.
单分子晶体管的电子和磁性特性很大程度上取决于分子电荷状态。单分子晶体管中的电荷传输的特点是库仑阻挡区域，其中分子的电荷状态是固定的，电流受到抑制，由高电导的顺序隧道区域分隔开。由于电极功函数的可变性，通常很难指定每个库仑阻挡区域中分子物质的电荷状态。在这项工作中，我们提供了一种简单而快速的方法，基于电子声子耦合特征和泡利不相容原理来分配库仑阻挡区域中分子物种的电荷状态，只需观察稳定图高电导区域中电流的不对称性。我们证明以这种方式确定的电荷态分配与通过塞曼分裂测量获得的电荷态分配一致。我们的方法适用于 77 K，而磁场相关的测量通常需要低温（低于 4 K）。由于分子结中电子-声子耦合的普遍存在，我们期望该方法能够广泛适用于基于单分子和石墨烯量子点的单电子晶体管。电荷态的正确分配使研究人员能够更好地了解单分子晶体管的基本电荷传输特性。
The electronic and magnetic properties of single-molecule transistors depend critically on the molecular charge state. Charge transport in single-molecule transistors is characterized by Coulomb-blocked regions in which the charge state of the molecule is fixed and current is suppressed, separated by high-conductance, sequential-tunneling regions. It is often difficult to assign the charge state of the molecular species in each Coulomb-blocked region due to variability in the work-function of the electrodes. In this work, we provide a simple and fast method to assign the charge state of the molecular species in the Coulomb-blocked regions based on signatures of electron-phonon coupling together with the Pauli-exclusion principle, simply by observing the asymmetry in the current in high-conductance regions of the stability diagram. We demonstrate that charge-state assignments determined in this way are consistent with those obtained from measurements of Zeeman splittings. Our method is applicable at 77 K, in contrast to magnetic-field-dependent measurements, which generally require low temperatures (below 4 K). Due to the ubiquity of electron-phonon coupling in molecular junctions, we expect this method to be widely applicable to single-electron transistors based on single molecules and graphene quantum dots. The correct assignment of charge states allows researchers to better understand the fundamental charge-transport properties of single-molecule transistors.