Molecular switching in azobenzene mixed monolayer on water surface was investigated by means of Maxwell-displacement-current (MDC) measurement. The condensation of pure azobenzene monolayers was losened as a result of the introduction of phospholipids into the monolayers. We discussed the direction and magnitude of MDC across the mixed monolayers as a function of the molecular area.

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Ionization potentials of metal/conducting polymer interfaces and conducting polymer/poly (p-pyridyl vinylene), PPyV, interfaces have been evaluated by low-energy photoelectron spectroscopic method and nano-interfacial electronic states were determined. At all the measured interfaces, shift of the vacuum level was observed, showing the formation of an interfacial electric dipolar layer. The shifts of the ionization potential at the interface could be expressed as a linear function of work function of the contact metal. However, for conducting polymers/indium-tin-oxide, (ITO), interfaces, nano-interfacial electronic states could not be determined, because of observed novel ionization potential behavior in these systems. The present results have clearly demonstrated that sufficient clarification of the interfacial electronic states is necessary for understanding the properties of the organic electronic devices.

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Several types of thin polyimide (PI) films are prepared by vapor deposition polymerization, and the electrical conduction has been investigated with low frequency voltage. The samples coated with plasma polymerized ethylene (PPE) or subjected to plasma are used to study the role of the polyimide-electrode interface in electrical conduction. Leakage current is reduced extremely by surface treatment, and the correlation between leakage current and surface topograph on PI has been investigated using AFM technique. Effect of PPE coating and the influence of roughness of the PI surface on the electrical conduction are discussed.

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The authors synthesized new fluoresent dyes with benzoxazole group and evaluated the electroluminescent (EL) properties of organic light-emitting-diodes (OLED) with new dyes as emitting material. Our OLED devices consist of 50nm-thick triphenyl diamine derivative (TPD) layer and 50nm-thick benzoxazole dye layer. The typical OLED device showed a luminance of over 300cd/m² at 10V. However, the EL efficiencies of these devices were not necessaarily high. Since these benzoxazole dyes have triphenylamine group, the holes easily flew out from TPD to AlLi cathode through benzoxazole dye layer. This leads to increase in the number of holes which do not contribute to hole-electron recombination. Then we synthesized a new benzoxazole dimer derivative without triphenylamine group. When the dimer devivative was doped into oxadiazole derivative (OXD), a blue (an emission peak, 430nm) but weak luminance was observed.

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The authors are investigating the influence on properties of vacuum-deposited thin films of organic dyes prepared applying magnetic fields. In spite of weak magnetic field intensity (0.1-0.3T), the effect of magnetic field could be observed in PL spectra and IR-RAS spectra on 10, 10'-Bianthrone (BA). The organic dyes whose PL spectra, X-ray diffraction pattern and IR-RAS spectra are changed by the application of magnetic field during preparation have inherent molecular orientation. On the other hand, the organic dyes whose those spectra do not depend on magnetic field are amorphous-like and do not have inherent molecular orientation. As kinetic energy (kT) is much larger than magnetic energy operating a molecule, a few molecules cannot maintain inherent molecular orientation. Therefore, the cluster orientated by magnetic field will be incorporated into the conventional large domain, so that the magnetic field effect on various properties can be observed. This paper introduces and discusses the typical experimental results on a magnetic orientation.

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Improvement of electrode/organic interface has been studied in organic electroluminescent diodes which consist of 8-hydroxyquinoline aluminum (Alq₃) and diamine derivative (TPD). Mono-layer size aluminum oxide (Al₂O₃) layer was inserted between TPD and indium tin oxide (ITO) anode. The improvement of emission has been observed in the diode with Al₂O₃ layer of 0.5-1nm in thickness inserted in the interface of anode metal and organic molecule. The mechanism of increase in emission efficiency has been discussed.

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Polymeric optical waveguide films have been developed with a view to optical interconnection module applications. Three fabrication processes are employed: (1) spin coating to form thick films, (2) reactive ion etching (RIE) to form core ridges, and (3) cutting with a diamond saw to form 45° mirrors. We evaluated the surface roughness of the fabricated films, core-ridges and mirrors using an atomic force microscope (AFM) and a scanning electron microscope (SEM), and discuss them in relation to the optical characteristics. Spin coating provides a uniform film with a roughness of less than 3nm. The etched surfaces of the core ridges fabricated by RIE have a roughness of less than 0.3μm, which suggests that this roughness causes the loss of the curved waveguide. The diamond saw cutting process generated a roughness of 50nm over the whole surface with occasional projections several hundred nanometers high, suggesting that this roughness causes the mirror loss.
We confirmed that it is possible to fabricate polymer optical waveguide films with sufficient levels of performance for use in optical interconnection modules.

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The photoelectric properties of Langmuir-Blodgett (LB) films, made of merocyanine, M-tetra-tert-butylphthalocyanine (M=Ni, Cu, OV) organic dye, have been studied. The films comprising Al electrode as low workfunction metal which is in contact with the dye layer was recognized to be Schottky barrier. The photoelectric characteristics have their origin in the Schottky barrier formed at the junction between the Al electrode and organic dye. Al/organic LB film/ITO structure were fabricated to investigate photoelectric properties. Mechanism of photoelectric effects are discussed on the basis of the J-V experimental results and the energy band.

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The unified surface anchoring energy, which has been proposed to describe the generalized anisotropic interaction between the iematic director and the substrate, is investigated for nematic slabs of cyano- and fluorinated liquid crystals on a polymer alignment layer. A saturation method including a conventional optical measurement method is employed to determine the inified surface anchoring energy. The temperature dependence of the unified surface anchoring energy for each nematic slab ias been measured.

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Ionization-assisted deposition method was used for the formation of either Alq emission layer or Mg electron injection electrode in the fabrication of organic electroluminescence (EL) devices. In order to reduce the radiation damage by ion bombardment at the interface, films were deposited in two stages, first by turning off the ionization followed by the deposition with accelerated ions. When the Alq layer was prepared by this method, the luminescence efficiency was considerably improved by applying the ion acceleration voltage of 100 V. For the preparation of the Mg layer, the ion irradiation worked in a different manner for different device characteristics such as luminance, efficiency and lifetime. The ionization-assisted deposition did not have much advantage in improving the luminance, while the lifetime was remarkably improved by using larger amount and higher energy ions. The result suggests that these device characteristics originate in different structural feature in the device, and that the film formation condition needs to be optimized individually for the interface formation and successive film growth. Due to the flexible and real-time controllability of the deposition parameters, the ionization-assisted deposition is a promising technique for constructing multi-layered thin film devices such as organic EL device.

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Copper phthalocyanine (CuPc) LB film devices were fabricated and the sensing properties of NO₂ gas were investigated. The CuPc LB films were deposited onto glass substrates or the glasses covered with three monolayers of cadmium arachidate LB films by the vertical dipping method. Two xylene solutions containing 0.1mM and 0.5mM CuPc were used as the spreading solution. The -A isotherms indicated the area per CuPc molecule at the water surface was small in the case using 0.5mM solution. which suggests the formation of bi-monolayer. The excellent depositions were carried out in the case using the glass substrates covered with the cadmium arachidate LB monolayers. The I-V characteristics of CuPc LB devices showed the hopping conduction in the LB films. The currents increased with time by the change of the atmosphere gas from N₂ to NO₂ and vice versa. The response spectra strongly dependent on the concentration of the spreading solution and the substrate. Especially, the responses with two steps were observed in the devices deposited on the glass substrates with the high concentration solution. The responses were tentatively estimated to be due to the adsorption of the NO₂ gas molecules on the LB films and the diffusion of NO₂ gas molecules into the LB films. The diffusion was thought to depend on the thickness and/or disorder of the LB films, and the atomic force microscopy measurement supported the results. These results are greatly useful for development of NO₂ gas sensors.

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Capacitance-Voltage (C-V) characteristic of ultra-thin polyimide (PI) Langmuir-Blodgett (LB) films is discussed theoretically and experimentally with taking into account the interfacial electrostatic phenomena and interfacial electronic states at the metal/PI LB film interface. It was found that the apparent film thickness decreases due to the charge exchange phenomena at the metal/film interface. It was also found that electrical insulating properties of Au/PI LB film/Al device depended on the polarity of external voltage, probably due to the formation of the electrostatic interfacial electric field of 10⁸-10⁹ V/m.

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We developed the novel preparation method to achieve a long driving lifetime for organic lightemitting-diode (OLED) and the multi-color emission from a device using thermal chemical vapor deposition (TCVD) polymer films. TCVD films were constructed of poly-p-xylylene (PPX) and poly-2-chloro-p-xylylene (PCPX). The TCVD films can be prepared at room temperature under a dry process without using organic and aqueous solvents. The lifetime of TCVD film-passivated OLED was about two times longer than that of naked OLED in vacuum. For multi-color device, after depositing about 1.2μm-thick TCVD films on a first OLED, we prepared a second OLED. Our proposing method is very effective and practical for the formation of full-color devices.

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Electrical conductivities of single piece of carbon micro coils are studied as functions of probe distance, stretch ratio and temperature. The micro coils have double helical structure with the diameter of several μm and the length of several mm. It is found that the conductivity of the single carbon micro coil is 50-100S/cm. The resistance increases by stretching due to disconnection between helices. The temperature dependence of conductivity shows the slight semiconductive behavior, indicating the variable range hopping.

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Polarization reversal process and light scattering at the instant of polarity reversal of applied voltage in the chiral smectic C phase of ferroelectric liquid crystal (FLC) using uniformly aligned thick cell has been studied. Polarizing microscopic observation of polarization reversal process has been performed. Transient stripe texture has been observed in polarization reversal process. Transmitted light through the cell has been diffracted by the periodical stripe texture. The direction of the stripe texture is tilted to the smectic layer and the tilt direction of the stripe texture depends on the polarity of applied voltage. Light scattering measurement has been performed upon applying rectangular voltage. Uniform scattered state has been performed under application of rectangular voltage in moderate frequency.

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We prepared high-quality monolayer Langmuir-Blodgett films using a novel molecule C37H40N404 synthesized by us. This molecule is the long-chain alkyl derivative which has dinitrobenzene moiety (acceptor subunit) and dihydrophenazine (donor subunit) bridged by a methylene group with constant distance and bond angle. It behaves as unimolecular device with the control of the potential between donor and acceptor subunits. We transferred the monolayer film onto a mica plate and succeeded in getting molecular images by AFM. Furthermore the monolayer was transferred onto Au (111) and manometer-scale rectifying or semiconducting characteristics were successfully obtained by using AFM I-V technique.

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We fabricated field effect transistors (FETs) using donor (TTF, TMTSF) and acceptor (TCNQ) molecules, and we investigated the change of conductivity in the charge transfer (CT) complex layer by applying gate voltages. Several types of FETs having TTF/TCNQ and TMTSF/TCNQ layered structures were examined. The stacked-layer FET showed a large transconductance compared with a single-layer FET. The experimental results demonstrate that the CT complex layer formed between donor and acceptor films mainly works as a conduction channel. Furthermore, the change in the degree of charge transfer corresponding to conductivity change was confirmed by infrared absorption spectra.

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The applicability of a method for the determination of localized-state distributions in disordered semiconductors to time-of-flight (TOF) photocurrent transients has been numerically examined. The method based on the analysis of the transient photocurrent using Laplace transform has been originally proposed for transient photoconductivity in the materials [H. Naito et al., Appl. Phys. Lett. 64, 1830 (1994)]. It is found that the method correctly works in case of TOF photocurrent transients as well. The improvement of the energy resolution of the method is shown to be possible using the Tikhonov regularization. The method is applied to the analysis of TOF photocurrent transients of poly (phenylene vinylene) (PPV) and poly (methylphenylsilane) (PMPS) thin films, which are promising materials as visible and ultraviolet light emitting diodes (LED), respectively. The results are compared with those of space-charge-limited-current measurements in PPV and PMPS LED's.

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