Implication of Current–Voltage Curve Shape in Molecular Electronics

Abstract

The transmission function, T(E), widely used as a toy model in molecular electronics, relies exclusively on a Lorentzian-shaped energy level. The shape of the energy level may be sensitive to the inhomogeneity of the active monolayer in a tunnel junction, yet it is usually ignored or underestimated in explaining the charge tunneling behavior. This article describes the interplay between the supramolecular packing feature of a selfassembled monolayer (SAM) and the shape of an energy level in T(E). Using a T(E) based on the Gaussian−Lorentzian product (GLP), line-fitting analysis was conducted over experimentally obtained current density− voltage curves of n-alkanethiolate SAMs to determine the mixing ratio between Gaussian and Lorentzian functions. It was revealed that the contribution of the Gaussian to the shape of the energy level in T(E) was dominant for solid-like SAMs whereas that of the Lorentzian was dominant for liquid-like SAMs. The energy-level shape also responded to defects induced by the surface roughness of the bottom electrode. We further demonstrated that our approach can be applied to rectifying junctions, using ferrocenyl-terminated n-alkanethiolate SAM. These findings indicate that shape analysis over the current−voltage curve, intimately related to the shape of the energy level of T(E), may provide implications for the packing features of SAMs reminiscent of spectral line fitting in spectroscopy.

Highly Effective and Efficient Self-Assembled Multilayer-Based Electrode Passivation for Operationally Stable and Reproducible Electrolyte-Gated Transistor Biosensors

“…19,24 However, because of the ultrathin nature of the SAM, the insulation property of the SAM film could be limited to provide sufficient protection for the electrodes with nonuniform or rough surfaces, particularly those produced through thermal evaporation and printing. 25,26 Therefore, it is highly desirable to develop a facile solution-processable, effective, and complete passivation method using an excellent insulating material applicable to a wide range of electrodes, thereby enabling the stable operation of EGT biosensors. Herein, we present a novel and rationally designed passivation method using a self-assembled multilayer (SAML) with highly effective insulation properties via a facile solution process for achieving the operational stability of EGT biosensors in aqueous electrolytes.…”

“…As one of the most widely used insulating materials, epoxy-based photoresists (e.g., SU-8) have been employed for the electrode passivation of devices. − However, photoresist-based passivation typically requires expensive equipment and complex procedures for photolithography, which make it neither feasible nor cost-effective for large-area fabrication and mass production. Alternatively, several groups have reported a simple, large-area, and cost-efficient solution-processed passivation method employing hydrophobic self-assembled monolayer (SAM) with long alkyl chains, which can be selectively deposited onto electrodes. − The hydrophobic SAM-based passivation approaches have shown excellent performances in EGT biosensors with uniform surfaces of metal electrodes. , However, because of the ultrathin nature of the SAM, the insulation property of the SAM film could be limited to provide sufficient protection for the electrodes with nonuniform or rough surfaces, particularly those produced through thermal evaporation and printing. , Therefore, it is highly desirable to develop a facile solution-processable, effective, and complete passivation method using an excellent insulating material applicable to a wide range of electrodes, thereby enabling the stable operation of EGT biosensors.…”

Tilt‐Engineered Molecular‐Scale Selector for Enhanced Learning in Artificial Neural Networks

“…In contrast to conventional pn and Schottky diodes based on 3D bulky and inorganic materials, charge transport in a molecular diode may strongly depend on the molecule conformations, [51,52] such as molecular tilt configuration, because of their discrete orbital levels that depend on the strength of the contact coupling and molecule-molecule interaction. [53][54][55][56][57][58][59] This peculiar factor to modify the electrical characteristics of the molecular junction could be used to design a suitable molecular selector that is compatible with the switching range of the synaptic device in an ANN.…”