Quantum interference mediated vertical molecular tunneling transistors

Molecular transistors operating in the quantum tunneling regime represent potential electronic building blocks for future integrated circuits. However, due to their complex fabrication processes and poor stability, traditional molecular transistors can only operate stably at cryogenic temperatures. Here, through a combined experimental and theoretical investigation, we demonstrate a new design of vertical molecular tunneling transistors, with stable switching operations up to room temperature, formed from cross-plane graphene/self-assembled monolayer (SAM)/gold heterostructures. We show that vertical molecular junctions formed from pseudo-p-bis((4-(acetylthio)phenyl)ethynyl)-p-[2,2]cyclophane (PCP) SAMs exhibit destructive quantum interference (QI) effects, which are absent in 1,4-bis(((4-acetylthio)phenyl)ethynyl)benzene (OPE3) SAMs. Consequently, the zero-bias differential conductance of the former is only about 2% of the latter, resulting in an enhanced on-off current ratio for (PCP) SAMs. Field-effect control is achieved using an ionic liquid gate, whose strong vertical electric field penetrates through the graphene layer and tunes the energy levels of the SAMs. The resulting on-off current ratio achieved in PCP SAMs can reach up to ~330, about one order of magnitude higher than that of OPE3 SAMs. The demonstration of molecular junctions with combined QI effect and gate tunability represents a critical step toward functional devices in future molecular-scale electronics.

Three-leg molecular transistors as molecular logic circuits: Design and modeling

The field of molecular electronics is a branch of science, which can have a variety of semiconductor technologies that extend beyond the silicon-based technology for the future. This branch of science may solve the limitations on size, high power usage and low speed in semiconductor technology. Rapid improvements in molecular electronics require modeling in the design of molecular devices. In this regard, we examine a three-leg molecule as a molecular transistor model and an indicator of methyl molecule as a resistance, in which the linkage of these abilities is carried out using LTspice simulation software. In order to investigate the effect of gated molecular on transport properties of the device, we design the half-adder molecular circuit and full-adder molecular circuit with them. The feasibility of building a prototype molecular transistor is illustrated using three-leg molecules directly contacted to gold electrodes, which the transmitted current from the structure is calculated using the Landauer formula. The application of the predicted results can be a base for designing moletronics devices.

Molecular electronics based on self-assembled monolayers

This article considers molecular electronics based on self-assembled monolayers. It begins with a brief overview of the nanofabrication of molecular devices, followed by a discussion of the electronic properties of several basic devices, from simple molecules such as molecular tunnel junctions and molecular semiconducting wires, to more complex ones such as molecular rectifying diodes. It also describes molecular switches and memories, focusing on three approaches called ‘conformational memory’, ‘charge-based memory’ and ‘RTD-based memory’ (RTD is resonant tunnelling diode). It shows that memory can be implemented from resonant tunnelling diodes following cell architecture already used for semiconductor devices. The article concludes with a review of molecular transistors.

Realizing bias-induced spin transition with high-spin MnII complexes at room temperature

Complexes in the ground state with high-spin magnetic ions (3d5/3d4) can be used to realize the electrically-induced spin-state transition and build room-temperature molecular transistors or memory devices.