Electrical Characteristics of Molecular Junctions Fabricated by Inverted Self-Assembled Monolayer Method.

In this study, we demonstrated the molecular ensemble junctions fabricated by the inverted selfassembled monolayer (iSAM) method in which the molecular layer was deposited on the top electrode surface. The alkyl thiolate molecules were used to benchmark this method and we found that the electrical characteristics of these molecular junctions were comparable to the results reported previously by performing statistical analysis. We expect this iSAM method to enable the molecular junctions with bottom electrode of various materials.

Intrinsic Optoelectronic Characteristics of MoS Phototransistors a Fully Transparent van der Waals Heterostructure.

In the past decade, intensive studies on monolayer MoS-based phototransistors have been carried out to achieve further enhanced optoelectronic characteristics. However, the intrinsic optoelectronic characteristics of monolayer MoS have still not been explored until now because of unintended interferences, such as multiple reflections of incident light originating from commonly used opaque substrates. This leads to overestimated photoresponsive characteristics inevitably due to the enhanced photogating and photoconductive effects.

Highly uniform monolayer graphene synthesis a facile pretreatment of copper catalyst substrates using an ammonium persulfate solution.

The demand for large-area, high-quality synthesis of graphene with chemical vapor deposition (CVD) has increased for the realization of next-generation transparent and flexible optoelectronic applications. In conventional CVD processes, various synthesis parameters can strongly affect the quality of the resultant graphene. In particular, surface engineering of a copper catalyst substrate is one of the most promising pathways for achieving high-quality graphene with excellent reproducibility.

Atomic switches of metallic point contacts by plasmonic heating.

Electronic switches with nanoscale dimensions satisfy an urgent demand for further device miniaturization. A recent heavily investigated approach for nanoswitches is the use of molecular junctions that employ photochromic molecules that toggle between two distinct isoforms. In contrast to the reports on this approach, we demonstrate that the conductance switch behavior can be realized with only a bare metallic contact without any molecules under light illumination.

Unidirectional Real-Time Photoswitching of Diarylethene Molecular Monolayer Junctions with Multilayer Graphene Electrodes.

We fabricate and characterize vertical molecular junctions consisting of self-assembled monolayers of diarylethene (DAE) contacted by a multilayer graphene (MLG) electrode on the top and gold on the bottom. The DAE molecular junctions show two stable electrical states, a closed state (high conductance) or an open state (low conductance), which are created upon illumination with UV or visible light, respectively. For the Au-DAE-MLG junction structure, we observe that the current levels between the two conductance states are separated by 2 orders of magnitude.

Enhanced Charge Injection Properties of Organic Field-Effect Transistor by Molecular Implantation Doping.

Organic semiconductors (OSCs) have been widely studied due to their merits such as mechanical flexibility, solution processability, and large-area fabrication. However, OSC devices still have to overcome contact resistance issues for better performances. Because of the Schottky contact at the metal-OSC interfaces, a non-ideal transfer curve feature often appears in the low-drain voltage region.

Interface-Engineered Charge-Transport Properties in Benzenedithiol Molecular Electronic Junctions via Chemically p-Doped Graphene Electrodes.

In this study, we fabricated and characterized vertical molecular junctions consisting of self-assembled monolayers of benzenedithiol (BDT) with a p-doped multilayer graphene electrode. The p-type doping of a graphene film was performed by treating pristine graphene (work function of ∼4.40 eV) with trifluoromethanesulfonic (TFMS) acid, producing a significantly increased work function (∼5.

Gate-dependent asymmetric transport characteristics in pentacene barristors with graphene electrodes.

We investigated the electrical characteristics and the charge transport mechanism of pentacene vertical hetero-structures with graphene electrodes. The devices are composed of vertical stacks of silicon, silicon dioxide, graphene, pentacene, and gold. These vertical heterojunctions exhibited distinct transport characteristics depending on the applied bias direction, which originates from different electrode contacts (graphene and gold contacts) to the pentacene layer.

Electrical characterization of benzenedithiolate molecular electronic devices with graphene electrodes on rigid and flexible substrates.

We investigated the electrical characteristics of molecular electronic devices consisting of benzenedithiolate self-assembled monolayers and a graphene electrode. We used the multilayer graphene electrode as a protective interlayer to prevent filamentary path formation during the evaporation of the top electrode in the vertical metal-molecule-metal junction structure. The devices were fabricated both on a rigid SiO2/Si substrate and on a flexible poly(ethylene terephthalate) substrate.

Statistical investigation of the length-dependent deviations in the electrical characteristics of molecular electronic junctions fabricated using the direct metal transfer method.

We fabricated and analyzed the electrical transport characteristics of vertical type alkanethiolate molecular junctions using the high-yield fabrication method that we previously reported. The electrical characteristics of the molecular electronic junctions were statistically collected and investigated in terms of current density and transport parameters based on the Simmons tunneling model, and we determined representative current-voltage characteristics of the molecular junctions. In particular, we examined the statistical variations in the length-dependent electrical characteristics, especially the Gaussian standard deviation σ of the current density histogram.

Statistical Analysis of Electrical Properties of Octanemonothiol versus Octanedithol in PEDOT:PSS-Electrode Molecular Junctions.

Unlabelled: We fabricated a large number of octanemonothiol (C8) and octanedithol (DC8) molecular electronic devices with

Pedot: PSS (3,4-ethylenedioxythiophene) interlayer and performed a statistical analysis on the electronic properties of these devices. From the analysis, we obtained the Gaussian plot of histograms of Log10 (current density (J)) and several statistical estimates such as arithmetic mean, median, Gaussian mean, arithmetic standard deviation, adjusted absolute median deviation, and Gaussian standard deviation. We determined the current density-voltage (J-V) characteristics from the statistically representative data for C8 and DC8 devices and found that the conductivity of C8 is higher than that of DC8 by a factor of ~10.

A new approach for high-yield metal-molecule-metal junctions by direct metal transfer method.

The realization of high-yield, stable molecular junctions has been a long-standing challenge in the field of molecular electronics research, and it is an essential prerequisite for characterizing and understanding the charge transport properties of molecular junctions prior to their device applications. Here, we introduce a new approach for obtaining high-yield, vertically structured metal-molecule-metal junctions in which the top metal electrodes are formed on alkanethiolate self-assembled monolayers by a direct metal transfer method without the use of any additional protecting interlayers in the junctions. The fabricated alkanethiolate molecular devices exhibited considerably improved device yields (∼70%) in comparison to the typical low device yields (less than a few %) of molecular junctions in which the top metal electrodes are fabricated using the conventional evaporation method.