Differential Conductance Switching of Planar Tunnel Junctions Mediated by Oxidation/Reduction of Functionally Protected Ferrocene

Abstract

Planar tunnel junctions were fabricated by self-assembling 1,1'- ferrocenedicarboxylic acid (FDCA) onto native oxides of thermally deposited aluminum films and subsequently depositing a second aluminum film. Junctions were characterized using Reflection-Absorption Fourier Transform Infrared Spectroscopy (RAIRS) and current-voltage (I-V) spectroscopy. Before deposition of the second aluminum film, RAIRS of FDCA and ferrocenecarboxylic acid (FCA) films revealed COO(-), C=O, and Fc ring stretching modes, indicating that both types of molecules can interact strongly with the oxide and remain intact. After deposition, systems exhibited prominent COO(-) modes and weakened C=O modes, indicating further reaction with aluminum/aluminum oxide. Fc ring modes persisted in FDCA systems but disappeared in FCA systems, suggesting that the second COOH group in the FDCA molecule can act as a protecting group for the ferrocene moiety. Cyclic I-V measurements of FDCA tunnel junction systems revealed very strong ( approximately 10-fold) hysteretic differential conductance switching that was both reversible and stable. Control measurements using as prepared junctions, as well as junctions containing 1,6-hexanedioic acid, 1,9-nonanedioic acid, 1,4-dibenzoic acid, or FCA revealed only very weak ( approximately 10%) differential conductance changes. We attribute FDCA junction switching to barrier profile modifications induced by oxidation/reduction of the functionally protected ferrocene moieties.

Amination of surfaces via self-assembly of dopamine

“…The sCA of Fc-terminated mica-DA monolayer is 45°, while Fc + -terminated dopamine monolayer has a lower CA of 23°due to more hydrophilic nature of the oxidized Fc + (Fig. 8a, inset), correlating well with the determined surface chemical composition [57]. X-ray photoelectron spectroscopy (XPS) was performed on the Si-DA (in black) and Si-DA-Fc (in red) to further verify the surface composition.…”

Electrochemically Assisted Fabrication of Metal Atomic Wires and Molecular Junctions by MCBJ and STM‐BJ Methods

“…Under electrochemical conditions, this kind of molecules exhibits interesting switching properties though the control of its ferrocene redox state. [81,[86][87][88] The dissymmetric monothiol parent of this molecule exhibits a fast redox reaction when self-assembled on gold electrodes, [89,90] establishing that electron transport is very efficient through this kind of molecule. Figure 10 shows three typical I-V curves for molecular junctions involving Fc-VPM molecules and different gap widths.…”

Redox-gated electron transport in electrically wired ferrocene molecules

“…The molecule is a good model system for studying electron transport phenomena also because it exhibits fast and reversible one-electron transfer on gold and other solid electrodes. Recent experiments have shown that ferrocene compounds exhibit negatively differential resistance (NDR) effect, which further demonstrates rich and interesting electronic properties of the molecule [25,[27][28][29]. In the present work, our focus is to determine how the conductance of ferrocene compounds chemically bound to two probing electrodes depends on the redox states.…”