Nanofabrication Techniques in Large-Area Molecular Electronic Devices

Abstract

The societal impact of the electronics industry is enormous—not to mention how this industry impinges on the global economy. The foreseen limits of the current technology—technical, economic, and sustainability issues—open the door to the search for successor technologies. In this context, molecular electronics has emerged as a promising candidate that, at least in the short-term, will not likely replace our silicon-based electronics, but improve its performance through a nascent hybrid technology. Such technology will take advantage of both the small dimensions of the molecules and new functionalities resulting from the quantum effects that govern the properties at the molecular scale. An optimization of interface engineering and integration of molecules to form densely integrated individually addressable arrays of molecules are two crucial aspects in the molecular electronics field. These challenges should be met to establish the bridge between organic functional materials and hard electronics required for the incorporation of such hybrid technology in the market. In this review, the most advanced methods for fabricating large-area molecular electronic devices are presented, highlighting their advantages and limitations. Special emphasis is focused on bottom-up methodologies for the fabrication of well-ordered and tightly-packed monolayers onto the bottom electrode, followed by a description of the top-contact deposition methods so far used.

A review of oligo(arylene ethynylene) derivatives in molecular junctions

“…5. These and other methods have been thoroughly described in many reviews, [18][19][20][21][22][23][24][25][26] so will not be subject to detailed discussion here. Some aspects of their development are discussed in section 1.3.…”

Experimental Validation of Quantum Circuit Rules in Molecular Junctions

“…Beyond junctions based on 'large area' contacts to large numbers of molecules in well ordered monolayers, [8][9][10][11] the development of techniques for the formation of single-molecule junctions such as the scanning tunnelling microscope break junction (STM-BJ), [12] current-distance spectroscopy (I(s)), [13] and mechanically controlled break-junctions (MCBJ) [14] have become essential experimental tools through which to probe the electrical properties and physical structure of molecular junctions in unprecedented detail. Through such studies, molecules that integrate within a junction to give electrical responses that correspond to wires, rectifiers, and switches have been developed, [15,16] while the introduction of a third 'gate' electrode to the junction assembly has allowed the demonstration of a transistor-like response at the single-molecule level.…”

Uncapped Gold Nanoparticles for the Metallization of Organic Monolayers

“…However, one of the main bottlenecks to be addressed en route to true large‐area molecular electronic junctions is the development of methodologies that permit top electrodes to be reliably fabricated onto the functional monolayer. [ 30–36 ]…”

“…These problems include penetration of high‐energy metal atoms through the monolayer during the deposition process resulting in short‐circuits and/or damage of the functional organic molecules in the monolayer, and low surface coverage of the monolayer by the top‐contact electrode. [ 30–36 ] Whilst the use of liquid materials as top contacts alleviates some of these issues, a liquid contact would force the use of encapsulation techniques that may not be compatible with large‐scale fabrication whilst also being reliant on toxic (Hg) or scarce (e‐GaIn) materials. The use of electron‐beam deposited carbon electrodes has met with great success in the fabrication of molecular junctions from robust molecular layers, but the nature of the equipment involved means that this technique is not readily accessible in many laboratories.…”