Modulated Rectification of Carboxylate-Terminated Self-Assembled Monolayer Junction by Humidity and Alkali Metal Ions: The Coupling and Asymmetric Factor Matter

Abstract

Facile modulation of the rectification behavior of a molecular junction device was achieved by humidity and alkali metal ions using a series of carboxylic acid-terminated self-assembled monolayers (COOH SAMs) on gold and eutectic gallium-indium alloy top contact (EGaIn). The rectification ratio (RR) increased significantly as the humidity (ranging from 1 to 39%) increases for an n-mercaptoalkanoic acid (HSC n O2H, n = 11, 12, 14, 16) SAM device. Meanwhile, K+/Na+, as the counterion of COO– in the same element group with H+, enhanced the RR of the SAM device as well. By the detailed study of the rectifying current–voltage (I–V) response using a theoretical model based on single-level tunneling, we found that the modulated rectification behavior of SAMs was attributed to the change in the coupling strength of the carboxylic group with the EGaIn electrode and the asymmetry factor of the junction in the presence of water and K+/Na+. Our study here suggested that the delicate electronic structure change at the molecule–(GaO x )­GaIn interface played the most significant role in the modulation of the rectification performance of the SAM device. The molecule–(GaO x )­GaIn interface thus offered a great research opportunity to achieve the desired function of SAM-GaIn-based molecular devices.

Modulated Structure and Rectification Properties of a Molecular Junction by a Mixed Self-Assembled Monolayer

“…Using the conventional thermal evaporation method, a 60 nm gold film was prepared on a clean Si(100) wafer with a SiO 2 layer. ,, The clean Si(100) wafer was placed inside a vapor deposition chamber. Chromium (5 nm) as an adhesive layer was evaporated followed by 60 nm Au at a vacuum of 1 × 10 –6 mbar with evaporation rates of 0.05 and 1.0 Å/s, respectively.…”

Chemical Conformation Induced Transport Carrier Switching in Molecular Junction based on Carboxylic-Terminated Thiol Molecules

“…It is unexpected since the electronic structure of the SAM layer in both cases is indistinguishable as listed in Table . We noticed that Ai et al among others reported the resistance of the SAM layer based on the carboxylic-terminated thiol molecule using EGaIn top contact was influenced by the humidity. However, in our junction, we exclude the effect of H 2 O used during the formation of the SAM layer since the low-bias resistance of Au/SC 11 COOH/Au is 2 orders of magnitude smaller than that of Au/SC 11 CH 3/ Au junction.…”

“…It is unexpected since the electronic structure of the SAM layer in both cases is indistinguishable as listed in Table 1. We noticed that Ai et al 21 among others 26 reported the resistance of the SAM layer based on the carboxylic-terminated thiol molecule using EGaIn top contact was influenced by the humidity. However, in our Next, we made AFM tips coated with other metals including Ag and Pt and then studied the effect of work functions on the low-bias resistance.…”

“…An important question in molecular electronics is to understand the relationship between molecular structures, either electronic − or conformation − structures, and transport characteristics and ultimately to achieve electronic functions such as a molecular rectifier − or conductance switcher. ,,− For instance, connecting to a meta- or para-position of a molecule, linear vs nonlinear, can lead to divergence in electrical conductance; , the dipole of molecules can induce the rectification property . Small changes in the conformation structure could result in large changes in intermolecular interaction that might impact the electronic behavior.…”

Ultraviolet Light-Sensitive Debonding Layer for Reducing Adhesion of Polymer Adhesives for Recycling

“…Here, a method for breaking adhesive interfaces is proposed and relies on the ability of one of the materials at the adhesive interface to be functionalized with a small molecule self-assembled debonding layer that contains a cleavable covalent bond. − Self-assembled thin layers, e.g., self-assembled monolayers (SAMs), have been used at a variety of interfaces for a number of different applications, such as surface reaction modifiers, chemical probes, electronics insulators, and adhesion promoters. − The method developed here depends on a chemical change in the system rather than a mechanical change to achieve debonding. Specifically, this research explores the ability of a silane-based debonding layer on silica to debond polymer adhesives from the silica surface.…”