Mixed Molecular Electronics: Tunneling Behaviors and Applications of Mixed Self‐Assembled Monolayers

Abstract

studies have relied on homogeneous, pure SAMs, that is, SAMs composed of one type of molecules. Contamination or dilution of a homogenous SAM by different molecules has typically been considered to cause negative effects because increased heterogeneity can directly translate into (supra)molecular and electronic structural changes, which can hinder the achievement of desired device performance.Although the field of molecular and organic electronics has long utilized pure molecular systems, studies on how charges traverse across multicomponent molecular systems have only recently emerged. [8] This review article focuses on the emergence of, and recent advances in mixed molecular electronics, defined as an electronics field exploiting heterogeneous molecular systems such as mixed SAMs (Figure 1). In this article, we introduce and discuss charge transport behaviors in mixed SAMs and applications for mixed molecular electronics. We further aim to provide a rational perspective on the unique features of mixed molecular systems with an eye toward potential molecular and nanoelectronics applications. Supramolecular and Electronic Structures of Mixed SAMs Supramolecular Structure of Mixed SAMsDiluting a pure, single-component SAM with another molecule leads to a mixed SAM. Depending on the number of molecular species comprising a mixed SAM, such a molecular dilution can yield binary, ternary, quaternary mixed SAMs, and so on. Mixed SAMs can be formed by several methods. Among others, the following three methods are commonly employed.

Correlating the Influence of Disulfides in Monolayers across Photoelectron Spectroscopy Wettability and Tunneling Charge-Transport

“… 14 − 19 The structural and interfacial properties of derivatives of alkanethiols in mixed monolayers were recently found to be closely related to the transport properties of tunneling junctions. 20 − 26 The special nature of this type of bonding is what imparts SAMs with some of their most useful properties, because it governs the dynamics of self-assembly and allows for the formation of densely packed monolayers as well as self-repair, in-place exchange, the formation of mixed monolayers, and responsiveness. Elucidating the special nature of covalent Au–S bonding on surfaces has, however, proven challenging.…”

Monitoring Solid‐Phase Reactions in Self‐Assembled Monolayers by Surface‐Enhanced Raman Spectroscopy

“…Thefunctionalization of solid surfaces with self-assembled monolayers (SAMs) is aw idely applied method for surface modifications with applications in catalysis, [1][2][3] chemical and biochemical sensing, [4][5][6] molecular electronics, [7][8][9] wettability, [10] corrosion prevention, [11] and many others.V arious functionalization methods rely on as tepwise assembly or am odification of the SAMs. [12] Due to the differences in the chemical and physical behavior of molecules attached to surfaces compared to their crystalline or liquid form, the composition of these molecular layers is ideally characterized upon each assembly and modification step.For such purposes, however, only af ew surface analytical methods exist that provide ahigh enough sensitivity to determine the elemental composition (X-ray photoelectron spectroscopy), the topology (scanning tunneling microscopy,a tomic force microscopy), the lattice structure (near-edge X-ray absorption fine structure spectroscopy), the surface layer thickness (ellipsometry), or the surface coverage (thermal gravimetric analysis and electrochemical methods).…”

Perfect isolation of π-conjugated molecules on inorganic surfaces with [1]rotaxane structure for enhancing electrical properties

“…where the conjugated molecules are diluted in a non-conjugated molecular monolayer, provide an isolated environment around the π-conjugation. [16][17][18] However, such methods require a low π-conjugation composition ratio, which is disadvantageous for electric devices. On the other hand, increasing the concentration of π-conjugated molecules induces the formation of aggregation structures on the surface of the material.…”