Dipole-Induced Rectification Across Ag^TS/SAM//Ga₂O₃/EGaIn Junctions

Abstract

This Article describes the relationship between molecular structure, and the rectification of tunneling current, in tunneling junctions based on self-assembled monolayers (SAMs). Molecular dipoles from simple organic functional groups (amide, urea, and thiourea) were introduced into junctions with the structure Ag TS /S(CH 2 ) n R(CH 2 ) m CH 3 // Ga 2 O 3 /EGaIn. Here, R is an n-alkyl fragment (−CH 2 −) 2 or 3 , an amide group (either −CONH− or −NHCO−), a urea group (−NHCONH−), or a thiourea group (−NHCSNH−). The amide, urea, or thiourea groups introduce a localized electric dipole moment into the SAM and change the polarizability of that section of the SAM, but do not produce large, electronically delocalized groups or change other aspects of the tunneling barrier. This local change in electronic properties correlates with a statistically significant, but not large, rectification of current (r + ) at ±1.0 V (up to r + ≈ 20). The results of this work demonstrate that the simplest form of rectification of current at ±1.0 V, in EGaIn junctions, is an interfacial effect, and is caused by a change in the work function of the SAM-modified silver electrode due to the proximity of the dipole associated with the amide (or related) group, and not to a change in the width or mean height of the tunneling barrier.

Mechanistic Framework for the Formation of Different Sulfur Species by Electron Irradiation of n-Dodecanethiol Self-Assembled Monolayers on Au(111) and Au(100)

“…• the electron in the Au surface, results in energy change of (equations [1] and [3]): [5] =where (8.41 eV) is the ionization energy of the = + -• radical in vacuum.…”

“…Moreover, it has been observed a renewed interest in fundamental research about thiolate-SAMs. For instance, the molecular origin of the odd-even effects 4 and whether a dipolar group modifies the electron-tunneling across SAMs 5 have been recently studied. The interest has been mainly triggered due to the wide range of applications of thiolate-SAMs in molecular electronic devices.…”

Tailoring the Interfacial Band Offset by the Molecular Dipole Orientation for a Molecular Heterojunction Selector

“…designed a specific molecular SAM with functional dipolar groups, exhibiting a rectification feature up to ≈20. [ 27 ] Kovalchuk et al. ascribed the dipole‐induced asymmetric tunneling conduction in eutectic Ga‐In/pyrimidyl‐based molecules/Au.…”

Ion Selective Nanochannels: From Critical Principles to Sensing and Biosensing Applications

“…[143] Various parameters such as surface charge distribution, electrical double layer properties, surface functional groups, surface modification of nanochannel/nanopore, electrolyte concen tration, electrolyte pH, size of nanopore/nanochannels, exter nally applied bias potential, ion concentration polarization, and geometry of nanodevice can affect the ICR in nanobased devices. [62,64,101,148,[153][154][155][156][157][158] Asymmetric ion distributions along a nanochannel can generate ICR. Some parts of the nanochannel have a positively charged surface in aqueous solu tions in diodelike nanochannels, while the other parts are nega tively charged.…”