The Use of Polyethyleneimine to Control the Growth-Front Morphology of Electrochemically Deposited Gold Nanowires for Engineered Nanogap Electrodes

Porous anodic alumina (PAA) has generated increasing attention over the past decade for its use as a sacrificial template in the electrochemical synthesis of high-aspect-ratio nanomaterials. However, a significant challenge that still remains unsolved concerns the control over the shape of the growth front of electrodeposited materials in a PAA template. The consensus of the molecular electronics community holds that many of the inconsistencies in the transport properties observed from a particular molecular device could be mitigated by better contact between the electrodes and molecule(s) of interest. In such cases, it becomes imperative that the contact interfaces on both sides of the molecular layer be flat on the molecular scale. This requirement is particularly relevant to ‘‘on-wire lithography’’ (OWL), where the inner segment of a tri-layered electrodeposited nanowire is selectively etched to achieve a nanogap of equivalent dimensions. The flat electrode surfaces could be expected to enable consistent measurements that would advance our understanding of the electrical characteristics of molecular systems. Similarly, the performance of a nanogap plasmonic antenna is sensitive to the shape of the metallic features and the gap between them