We present a novel synthetic method for a chiral conjugated polymer represented by helical polyacetylene. The method is based on chiral nematic liquid crystal (LC) that is used as an asymmetric reaction field for acetylene polymerization. The chiral nematic LC is prepared by adding a small amount of chiral compound such as biaxially chiral binaphthyl derivative into nematic LC. The asymmetric reaction field is constructed by dissolving Ziegler-Natta catalyst into the chiral nematic LC. The interfacial acetylene polymerization under the asymmetric reaction field gives rise to helical polyacetylene with one-handed screwed fibril morphology. It should be emphasized that a method analogous to that using chiral nematic LC is also feasible for other kinds of helical aromatic conjugated homo- and co-polymers, which might allow us to disclose uncultivated fields of liquid crystal in polymer synthesis.

Chiral liquid crystals such as cholesteric liquid crystal and chiral smectic liquid crystal form a spiral molecular alignment whose periodicity can be tuned upon molecular design in a large range between 100 nm and several hundreds of micrometers. Recently, studies have been carried out on photonic band gap materials based on chiral liquid crystals forming spiral periodic structures with a periodicity of the order of optical wavelengths. In this report, 1-D photonic band characteristics in cholesteric liquid crystal, ferroelectric liquid crystal (chiral smectic liquid crystal) and polymerized cholesteric liquid crystal are reviewed and laser actions in these systems are described. The photonic defect structure and optical localized state characteristic of the spiral periodic structure are also discussed.

The Ge device is one of the post-Si device candidates. Historically, Ge research started earlier than Si one, but the present society is constructed of Si technology. Why is Ge required again, what are the challenges, and what is the present status? The most important issue of Ge technology is the interface control, including insulator/Ge and metal/Ge, which are very fundamental issues of semiconductor technology, but very different from those of Si. In this paper we introduce the results obtained to date in our group.

The key to realizing high performance organic devices using conjugated polymers is the successful fabrication of a highly organized structure on a surface on a single molecule scale. Here, we have demonstrated a unique single-molecule processing-technique using electrochemistry, called ‘electrochemical epitaxial polymerization’. This technique is based on the step-by-step electropolymerization of a monomer along a lattice of iodine on a gold electrode surface to form single conjugated-polymer wires by applying voltage pulses to a monomer-electrolyte solution. By using this technique, we have succeeded in building a uniform high-density array of single conjugated-polymer wires on an electrode as long as 200 nm, controlling the wire’s density, length and direction. This first observation will open the door to the mass-production of single molecule-scale devices using conjugated polymers.

Recent organic light-emitting diodes (OLEDs) have realized the ultimate electroluminescence efficiency of nearly 100% using organometallic phosphorescent materials. In this paper, we describe the basic photoluminescence characteristics and the concentration quenching of iridium complexes in a solid state and in solution. We propose material and device structure designs aimed at high-efficiency OLEDs.

π-Conjugating oligomers in which a couple of thiophene and phenylene units are chained show structure-dependent visible fluorescence with a high quantum efficiency. Low-dimensional crystals self-assembled with these oligomers confine their fluorescence internally, resulting in novel light-emission phenomena. One of these phenomena is a lasing action based on stimulated resonance Raman scattering under the optical pumping of a crystal at the 0-0 absorption band. Another is pulse-shaped emission with a definite time delay under high-energy pumping at low temperatures. Both can be related to cooperative phenomena among the uniaxially oriented transition dipoles of the oligomer in the low-dimensional crystal.

A plasmonic metamaterial is an artificially micro/nano-structured material. It can reveal extraordinary properties such as negative refractive index or magnetic response which have never been observed for natural materials in the optical frequency region. In this report, we explain the mechanism and dispersion properties of a metamaterial investigated at optical frequencies. An application of metamaterials in novel optical devices is also proposed.

Semiconductor one-dimensional silicon nanowires (SiNWs) are attractive as the building blocks of future vertical-type semiconductor devices such as surrounding gate field-effect transistors. For their realization, it is indispensable to investigate the control of synthesis, arraignment, and electrical properties. In this report, we introduce the size control of SiNWs using compressive stress and the self-limiting oxidation effect due to thermal oxidation. Furthermore, we introduce impurity doping and the phonon confinement in SiNWs.

We have developed a new in-situ observation technique using electron spin resonance to detect the dynamic processes of defect creation under thin-film growth and surface modification. In this article, we show that the semiconductor device fabrication process creates many dangling bonds and its control is a key process, on the basis of experimental results of silicon oxidation, amorphous silicon growth, and SiO₂ etching.

On the basis of quantum mechanics as first principles for atomic-scale and nanoscale materials, we predict the surface reactions, catalytic reactions, electronic structures of interfaces between organic materials and metals, and the dynamics of defects in condensed matter using ab initio molecular dynamics. We design a new chemical reaction and the gettering center of copper impurities in silicon based on physical mechanisms. We show the powerful effectiveness of ab initio calculation by choosing the design of a fabrication method of diamond from graphite by electronic excitations.