In Operando Modulation of Rectification in Molecular Tunneling Junctions Comprising Reconfigurable Molecular Self‐Assemblies

Qiu, Xinkai; Rousseva, Sylvia; Ye, Gang; Hummelen, Jan C.

doi:10.1002/adma.202006109

Cited by 26 publications

(22 citation statements)

References 43 publications

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“…The relationship between the structure of SAM and charge transport across the SAM is the main part of our study. The NH 2 -SAM is sandwiched between a Au bottom electrode and a GaO x /EGaIn top electrode (Figure b). − ,,,,,,− To confirm the reliability of our measurement, we first measured the J – V curves of the aromatic SH SAM (TPT) junction as a control experiment. The distribution of log| J | was 0.91 ± 0.35 at +0.5 V (Figure S4), in line with the value reported in the literature …”

Section: Results and Discussionmentioning

confidence: 89%

Amine-Anchored Aromatic Self-Assembled Monolayer Junction: Structure and Electric Transport Properties

Tian

Martine

et al. 2021

Langmuir

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We studied the structure and transport properties of aromatic amine self-assembled monolayers (NH2-SAMs) on an Au surface. The oligophenylene and oligoacene amines with variable lengths can form a densely packed and uniform monolayer under proper assembly conditions. Molecular junctions incorporating an eutectic Ga–In (EGaIn) top electrode were used to characterize the charge transport properties of the amine monolayer. The current density J of the junction decreases exponentially with the molecular length (d), as J = J 0 exp(−βd), which is a sign of tunneling transport, with indistinguishable values of J 0 and β for NH2-SAMs of oligophenylene and oligoacene, indicating a similar molecule–electrode contact and tunneling barrier for two groups of molecules. Compared with the oligophenylene and oligoacene molecules with thiol (SH) as the anchor group, a similar β value (∼0.35 Å‑1) of the aromatic NH2-SAM suggests a similar tunneling barrier, while a lower (by 2 orders of magnitude) injection current J 0 is attributed to lower electronic coupling Γ of the amine group with the electrode. These observations are further supported by single-level tunneling model fitting. Our study here demonstrates the NH2-SAMs can work as an effective active layer for molecular junctions, and provide key physical parameters for the charge transport, paving the road for their applications in functional devices.

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Section: Results and Discussionmentioning

confidence: 89%

Amine-Anchored Aromatic Self-Assembled Monolayer Junction: Structure and Electric Transport Properties

Tian

Martine

et al. 2021

Langmuir

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“…We placed the sample on the sample stage and connected the grounded Au surface to the negative port of the source meter (6430 Sub-Femtoamp Remote SourceMeter, Keithley). The eutectic gallium-indium (EGaIn, 75.5% Ga and 24.5% In) in a microinjector was used as the top electrode and connected to the port of the source meter, which is a common method to build a molecular junction. ,,− The liquid metal forms a GaO x (average thickness of 0.7 nm) oxide layer when exposed to air. − We used a syringe to squeeze out the EGaIn droplet and brought it in contact with a clean gold surface and then slowly moved the syringe upward to form a conical EGaIn tip, followed by gently making contact with the samples (contact area ∼ 300 μm 2 ). A bias voltage was applied to the EGaIn tip, the J – V curve was scanned from 0 → +1.5 → −1.5 → 0 V with a step size of 200 mV, and the delay time between each step of applying the bias voltage was 0.08 s. For each new tip, we formed three junctions in 3–4 positions on one sample.…”

Section: Methodsmentioning

confidence: 99%

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

Tian

Song

et al. 2021

J. Phys. Chem. C

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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.

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“…Largearea molecular junctions comprising self-assembled monolayers (SAMs) could be used to study the reversible and reproducible conductance switching at ambient conditions. [22] We fabricated SAMs of E-PCIH as described in Supporting Information (Section:T he Fabrication of SAMs). And the characterizations of SAMs via atomic force microscopy (AFM), and angle-resolved X-ray photoelectron spectroscopy (ARXPS) are detailed in Supporting Information (Section:SAMs Characterization).…”

Section: Methodsmentioning

confidence: 99%

Single Dynamic Covalent Bond Tailored Responsive Molecular Junctions

Zhou

et al. 2021

Angewandte Chemie

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Responsive molecular devices are one of the core units for molecular electronics, and dynamic covalent bonds (DCBs) provide the opportunity for the fabrication of responsive molecular devices. Herein we employ a single dynamic acyl hydrazone bond to fabricate tailored molecular devices using the scanning tunneling microscopy break‐junction technique (STM‐BJ) and the eutectic Ga‐In technique (EGaIn). We found that the single‐DCB‐tailored molecular devices exhibited acid‐base and/or photo‐thermal response with three well‐defined molecular conductance states. The reversible switching has the ON/OFF ratio of ≈10 between each state for single‐molecule junctions and ≈3 for the SAMs‐based molecular junctions. Combined with the density functional theory calculations, we revealed that the multiple conductance states of these molecular junctions originate from the dynamic acyl hydrazone bond exchange and C=N isomerization. Our work opens the avenue towards the design of tailored single‐molecule electrical devices by implanting dynamic covalent bonds in molecular architectures.

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In Operando Modulation of Rectification in Molecular Tunneling Junctions Comprising Reconfigurable Molecular Self‐Assemblies

Cited by 26 publications

References 43 publications

Amine-Anchored Aromatic Self-Assembled Monolayer Junction: Structure and Electric Transport Properties

Amine-Anchored Aromatic Self-Assembled Monolayer Junction: Structure and Electric Transport Properties

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

Single Dynamic Covalent Bond Tailored Responsive Molecular Junctions

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