Greenwald Julia E, Cameron Joseph, Findlay Neil J, Fu Tianren, Gunasekaran Suman, Skabara Peter J, Venkataraman Latha
Department of Chemistry, Columbia University, New York, NY, USA.
WestCHEM, School of Chemistry, University of Glasgow, Glasgow, UK.
Nat Nanotechnol. 2021 Mar;16(3):313-317. doi: 10.1038/s41565-020-00807-x. Epub 2020 Dec 7.
To rival the performance of modern integrated circuits, single-molecule devices must be designed to exhibit extremely nonlinear current-voltage (I-V) characteristics. A common approach is to design molecular backbones where destructive quantum interference (QI) between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) produces a nonlinear energy-dependent tunnelling probability near the electrode Fermi energy (E). However, tuning such systems is not straightforward, as aligning the frontier orbitals to E is hard to control. Here, we instead create a molecular system where constructive QI between the HOMO and LUMO is suppressed and destructive QI between the HOMO and strongly coupled occupied orbitals of opposite phase is enhanced. We use a series of fluorene oligomers containing a central benzothiadiazole unit to demonstrate that this strategy can be used to create highly nonlinear single-molecule circuits. Notably, we are able to reproducibly modulate the conductance of a 6-nm molecule by a factor of more than 10.
为了与现代集成电路的性能相媲美，单分子器件必须设计成具有极其非线性的电流-电压（I-V）特性。一种常见的方法是设计分子主链，其中最高占据分子轨道（HOMO）和最低未占据分子轨道（LUMO）之间的破坏性量子干涉（QI）在电极费米能量（E）附近产生与能量相关的非线性隧穿概率。然而，调整这样的系统并不简单，因为将前沿轨道与E对齐很难控制。在这里，我们转而创建一个分子系统，其中HOMO和LUMO之间的相长性QI被抑制，而HOMO和相反相位的强耦合占据轨道之间的相消性QI被增强。我们使用一系列含有中心苯并噻二唑单元的芴低聚物来证明这种策略可用于创建高度非线性的单分子电路。值得注意的是，我们能够以超过10倍的系数可重复地调制一个6纳米分子的电导。
