Atomic switches: atomic-movement-controlled nanodevices for new types of computing.

Atomic switches are nanoionic devices that control the diffusion of metal cations and their reduction/oxidation processes in the switching operation to form/annihilate a metal atomic bridge, which is a conductive path between two electrodes in the on-state. In contrast to conventional semiconductor devices, atomic switches can provide a highly conductive channel even if their size is of nanometer order. In addition to their small size and low on-resistance, their nonvolatility has enabled the development of new types of programmable devices, which may achieve all the required functions on a single chip. Three-terminal atomic switches have also been developed, in which the formation and annihilation of a metal atomic bridge between a source electrode and a drain electrode are controlled by a third (gate) electrode. Three-terminal atomic switches are expected to enhance the development of new types of logic circuits, such as nonvolatile logic. The recent development of atomic switches that use a metal oxide as the ionic conductive material has enabled the integration of atomic switches with complementary metal-oxide-semiconductor (CMOS) devices, which will facilitate the commercialization of atomic switches. The novel characteristics of atomic switches, such as their learning and photosensing abilities, are also introduced in the latter part of this review.

Syntheses, crystal structures, and spectral properties of a series of 3,8-Bisphenyl-1,10-phenanthroline derivatives: precursors of 3,8-Bis(4-mercaptophenyl)-1,10-phenanthroline and Its ruthenium(II) complex for preparing nanocomposite junctions with gold nanoparticles between 1 microm gap gold electrodes.

A multistep synthesis was achieved to obtain 3,8-bis(4-mercaptophenyl)-1,10-phenanthroline, which has two free thiol end groups with a molecular length of 1.89 nm, and its ruthenium(II) complex. Five single-crystal structures and UV-vis spectra of related intermediates in methanol and the solid state were studied in order to obtain additional information on the molecules as well as on the supramolecular interactions in the structures. Thermal and electrochemical properties of related Ru(II) complexes were also involved. 3,8-Bis(4-mercaptophenyl)-1,10-phenanthroline and one of its ruthenium(II) complexes were then treated with gold nanoparticles (Au-NPs) via in situ thiol-to-thiol ligand exchange in the presence of two facing Au electrodes with a 1 x 1 microm(2) gap. Stable molecular junctions composed of self-assembled films were produced as revealed by an obvious increase of the conductivity between the Au electrodes, wherein dithiols-bridged Au-NPs were attached to the electrodes by means of Au-S-bonded contacts. Temperature-dependent current-voltage (I-V) measurements for the junctions were performed in the temperature range of 7-300 K, and classical Arrhenius plots and their linear fits were obtained to determine the average activation energies (DeltaE) of these devices. It is found that when the Ru(II) ion is introduced, the conductivity of the nanodevice is increased and the energy barrier is lowered under the same experimental conditions.