Electrostatic Fermi level tuning in large-scale self-assembled monolayers of oligo(phenylene-ethynylene) derivatives.
Electrostatic Fermi level tuning in large-scale self-assembled monolayers of oligo(phenylene-ethynylene) derivatives.
复制标题
低聚（亚苯基-乙炔基）衍生物大规模自组装单层的静电费米能级调谐。
DOI：
10.1039/d2nh00241h
复制
发表时间：
2022
影响因子：
9.7
通讯作者：
Wang X
中科院分区：
文献类型：
--
作者：
Wang X
理解和控制电极之间分子的轨道排列是设计实际应用的分子和纳米级电子器件的关键。轨道排列高度决定于分子-电极界面。轨道排列对单分子结的分子锚基团的依赖性已经被深入研究;然而，当将单分子按比例放大到大的平行分子阵列（如自组装单层（SAM））时，需要解决两个挑战：大多数期望的锚基团不形成高质量SAM。2.在SAM结中，通过栅电压调节前沿分子轨道比在单分子结中困难得多。在这项工作中，我们研究了分子-电极界面在自组装膜中的作用与微孔装置，使用最近开发的四足锚来克服挑战1，并结合单层石墨烯顶部电极与离子液体门来解决挑战2。不同分子的零偏轨道排列通过具有不同锚定基团的分子的电导最小值与栅极电压的偏移来表示。具有相同骨架但不同分子-电极界面的分子在实验上显示出在零偏压附近具有相差5倍的电导。使用密度泛函理论的理论计算支持在实验数据中观察到的趋势。这项工作揭示了如何控制分子结中HOMO-LUMO能隙内的电子传输，并将适用于未来器件应用的分子电子系统。
Understanding and controlling the orbital alignment of molecules placed between electrodes is essential in the design of practically-applicable molecular and nanoscale electronic devices. The orbital alignment is highly determined by the molecule–electrode interface. Dependence of orbital alignment on the molecular anchor group for single molecular junctions has been intensively studied; however, when scaling-up single molecules to large parallel molecular arrays (like self-assembled monolayers (SAMs)), two challenges need to be addressed: 1. Most desired anchor groups do not form high quality SAMs. 2. It is much harder to tune the frontier molecular orbitals via a gate voltage in SAM junctions than in single molecular junctions. In this work, we studied the effect of the molecule–electrode interface in SAMs with a micro-pore device, using a recently developed tetrapodal anchor to overcome challenge 1, and the combination of a single layered graphene top electrode with an ionic liquid gate to solve challenge 2. The zero-bias orbital alignment of different molecules was signalled by a shift in conductance minimum vs. gate voltage for molecules with different anchoring groups. Molecules with the same backbone, but a different molecule–electrode interface, were shown experimentally to have conductances that differ by a factor of 5 near zero bias. Theoretical calculations using density functional theory support the trends observed in the experimental data. This work sheds light on how to control electron transport within the HOMO–LUMO energy gap in molecular junctions and will be applicable in scaling up molecular electronic systems for future device applications.