Electronic transport through ruthenium-based redox-active organometallic molecules is measured by self-assembling diruthenium(III) tetra(2-anilinopyridinate)-di(4-thiolphenylethynyl) (trans-Ru2(ap)4(C'CC6H4S-)2 (A) and trans- Ru2(ap)4((C'CC6H4)2S-)2 (B) molecules in nanogap molecular junctions. Voltage sweeps at a high scan rate show low bias current peaks (at +/-0.35 +/- 0.05 V for A and +/-0.27 +/- 0.05 V for B), which change to plateaus in slow bias scans and a second conductance peak at approximately +/-1.05 +/- 0.15 V. The peaks/plateaus are not observed in the return bias sweeps, possibly due to charge storage in the molecules. The energy states for the molecular orbitals of these molecules as estimated from the conductance peaks are in close agreement with the respective energy values from voltammetric measurements in solution.

This letter describes a technique for realizing a gold ͑Au͒ surface with roughness at the atomic scale using techniques compatible with integrated device fabrication. The Au layer is electron-beam evaporated on a self-assembled monolayer of ͑3-Mercaptopropyl͒ trimethoxysilane on an oxidized silicon substrate and shows a root-mean-square surface roughness of ϳ2 Å over a 1 m 2 area. The physical stability of the Au film toward commonly used chemicals and processes for photolithography and self-assembly, and its suitability for formation of well-ordered organic monolayers indicate that the films are well suited as substrates for future device fabrication in molecular electronics or other devices involving self-assembled monolayers.

This paper presents a study of sequence specific electronic conduction through short (15-base-pair) double-stranded (ds) DNA molecules, measured by immobilizing 3 -thiol-derivatized DNAs in nanometre scale gaps between gold electrodes. The polycation spermidine was used to stabilize the ds-DNA structure, allowing electrical measurements to be performed in a dry state. For specific sequences, the conductivity was observed to scale with the surface density of immobilized DNA, which can be controlled by the buffer concentration. A series of 15-base DNA oligonucleotide pairs, in which the centre sequence of five base pairs was changed from G:C to A:T pairs, has been studied. The conductivity per molecule is observed to decrease exponentially with the number of adjacent A:T pairs replacing G:C pairs, consistent with a barrier at the A:T sites. Conductance-based devices for short DNA sequences could provide sensing approaches with direct electrical readout, as well as label-free detection.

Conformations and charge transport characteristics of biphenyldithiol self-assembled-monolayer molecular electronic devices: A multiscale computational study Theoretical investigation on electron transport through an organic molecule: Effect of the contact structure

Abstract-Pairs of electrodes with nanometer separation (nanogap) are achieved through an electromigration-induced break-junction (EIBJ) technique at room temperature. Lithographically defined gold (Au) wires are formed by e-beam evaporation over oxide-coated silicon substrates silanized with (3-Mercaptopropyl)trimethoxysilane (MPTMS) and then subjected to electromigration at room temperature to create a nanometer scale gap between the two newly formed Au electrodes. The MPTMS is an efficient adhesive monolayer between SiO 2 and Au. Although the Au wires are initially 2 m wide, gaps with length 1 nm and width 5 nm are observed after breaking and imaging through a field effect scanning electron microscope. This technique eliminates the presence of any residual metal interlink in the adhesion layer (chromium or titanium for Au deposition over SiO 2 ) after breaking the gold wire, and it is much easier to implement than the commonly used low-temperature EIBJ technique which needs to be executed at 4.2 K. Metal-molecule-metal structures with symmetrical metal-molecule contacts at both ends of the molecule are fabricated by forming a self-assembled monolayer of -dithiol molecules between the EIBJ-created Au electrodes with nanometer separation. Electrical conduction through single molecules of 1,4-Benzenedimethanethiol (XYL) is tested using the Au/XYL/Au structure with chemisorbed gold-sulfur coupling at both contacts.

Schottky barrier height of Au on the transparent semiconducting oxide β-Ga2O3 Appl. Phys. Lett. 101, 132106 (2012) Redox reaction based negative differential resistance and bistability in nanoparticulate ZnO films J. Appl. Phys. 112, 024314 (2012) InGaN metal-semiconductor-metal photodetectors with triethylgallium precursor and unactivated Mg-doped GaN cap layers J. Appl. Phys. 110, 083113 (2011) Investigation on the origin of the memory effect in metal/organic semiconductor/metal structures J. Appl. Phys. 110, 084508 (2011) Polarity reversal in bipolar resistive switching in Pr0.7Ca0.3MnO3 noble metal sandwich structures

We report the experimental investigations on space charge limited current (SCLC) and injection limited current (ILC) in copper phthalocyanine (CuPc), sandwiched between two metal electrodes. Thickness dependence of current-voltage characteristics of SCLC and ILC is accurately reproduced by the electric field and temperature dependent charge carrier mobility, without invoking charge density dependent mobility. These results are interpreted using a consistent description of SCLC and ILC, based on a unified model of hopping transport within Gaussian density of states in CuPc.

We report an electric-field-induced conductance transition from an insulating state to a conducting state in a thin layer of Alq3 sandwiched between two metal electrodes. Field-induced switching behavior with a high on-off ratio of ∼105 is observed in the devices, in which the cathode electrode is Al and the anode electrode is varied including Al, Au, and indium tin oxide. The switching behavior is absent in devices in which both electrodes have a high work function, indicating that efficient electron injection has an important role in the electric-field-induced switching behavior of Alq3-based single-layer devices.