Department of Chemistry and International Institute for Nanotechnology, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, USA.
Nano Lett. 2009 Dec;9(12):3974-9. doi: 10.1021/nl9018726.
We report a simple and reproducible method for fabricating heterometallic nanogaps, which are made of two different metal nanorods separated by a nanometer-sized gap. The method is based upon on-wire lithography, which is a chemically enabled technique used to synthesize a wide variety of nanowire-based structures (e.g., nanogaps and disk arrays). This method can be used to fabricate pairs of metallic electrodes, which exhibit distinct work functions and are separated by gaps as small as 2 nm. Furthermore, we demonstrate that a symmetric thiol-terminated molecule can be assembled into such heterometallic nanogaps to form molecular transport junctions (MTJs) that exhibit molecular diode behavior. Theoretical calculations demonstrate that the coupling strength between gold and sulfur (Au-S) is 2.5 times stronger than that of Pt-S. In addition, the structures form Raman hot spots in the gap, allowing the spectroscopic characterization of the molecules that make up the MTJs.
我们报告了一种简单且可重现的方法来制造异质金属纳米间隙，它由两个通过纳米级间隙隔开的不同金属纳米棒组成。该方法基于在线光刻技术，这是一种用于合成各种基于纳米线的结构（例如纳米间隙和盘阵列）的化学增强技术。该方法可用于制造对金属电极，其表现出明显的功函数，并通过小至 2nm 的间隙分离。此外，我们证明可以将对称的硫醇封端分子组装到这种异质金属纳米间隙中，以形成表现出分子二极管行为的分子输运结 (MTJ)。理论计算表明，金与硫 (Au-S) 的耦合强度比铂与硫 (Pt-S) 的耦合强度强 2.5 倍。此外，这些结构在间隙中形成拉曼热点，从而可以对构成 MTJ 的分子进行光谱特性分析。
