Evaluation techniques and the device applications of organic and composite thin films are described. One of the evaluation techniques is the surface plasmon resonance (SPR) spectroscopy. It has become a widely accepted method for the characterization and study of ultrathin films, interfaces and kinetic processes at surfaces, and it has been investigated in the applications of SPR sensors and plasmonic novel devices. Properties, functionalization and various applications of hybrid materials, nanocomposites, and nanoparticles are also introduced, and the application to industry is mentioned. Moreover, electronic device application of monolithic organic logic circuit using a stacked structure of two organic static induction transistors is explained. The advantages of this novel device structure are the controllability of the operational characteristics and simple device fabrication process.

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Dye-sensitized solar cells were fabricated using natural dyes and synthesized dyes in which rear metal was not contained. Effects of pH of dyes on the characteristics of the dye-sensitized solar cells were also examined. As a result, it was found that the conversion efficiency of the dye-sensitized solar cell fabricated using red-cabbage dye with a pH of 2.5 was 0.10 point larger than that of the solar cell fabricated using red-cabbage dye with a pH of 4.0. It was also found that the conversion efficiency of the solar cell fabricated using red-perilla dye with a pH of 3.1 was 0.10 point larger than that of the solar cell fabricated using red-perilla dye with a pH of 5.8. The results are discussed on the bases of the molecular structure of mainly contained dye and the optical absorption spectra.

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The hybrid ultra-thin films composed of cationic long-alkyl chain molecules and nano-size Prussian Blue clusters were obtained by the Langmuir-Blodgett (LB) technique. It was found that the LB films are quite useful as the starting material for building the high performance biosensors based on oxidative enzymes. The biosensors were easily prepared by a simple immersion of the LB films into enzyme solution, then they work under a very low potential range avoiding the interferent current. We demonstrated that the process is applicable to prepare many types of biosensors just by changing the immobilized enzymes.

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Thin films were sputtered onto copper substrates with a polyimide target by a conventional r.f. sputtering apparatus. Sputtered thin films were characterized by XPS and FT-IR. Sputtering conditions, i.e., pressures and r.f. power during sputtering influenced on the elemental compositions and chemical bonding states of the thin films.
Friction coefficients and wear durabilities of these sputtered thin films were evaluated by a pin-on-disk type scratch tester. Friction coefficients of the thin films were almost the same values as that of bulk material. Wear durability was improved by increase of the pressure and decrease of the r.f. power.
Adhesion strengths between these thin films and copper substrates were evaluated by a pull test apparatus. Adhesion strengths between the thin films and copper substrate were also improved by increase of the pressure and decrease of the r.f. power. Shear stresses of these sputtered thin films were measured by SAICAS^®. Shear stresses of the sputtered thin films were improved by increase of the pressure.
Contact angle of water droplets was decreased by increase the pressure and decrease the r.f. power.

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Organic donor/acceptor bilayers form a two-dimensional charge sheet composed of electron-hole pairs at their heterointerfaces due to formation of charge-transfer (CT) complexes. The CT induces electron-hole pairs which are useful for carrier transport in both vertical and lateral direction, providing novel electronic device applications. Here, we fabricated a two-dimensional charge sheet using organic donor/acceptor heterointerfaces and investigated its electrical behavior. Further, we revealed that conductive CT interfaces are generated by stacking almost monolayer of donor and acceptor thin films. These novel charge induction mechanisms will provide a new principle for designing organic devices.

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A high performance organic thin film transistor (OTFT) structure is proposed based on a device simulation, which enables higher current gain as compared with a conventional device structure. The device simulator makes it possible to derive current-voltage (I-V) characteristics, potential distribution and carrier concentration inside a device by solving Poisson's equation and continuity equation. It is made clear that the device performances improve more than twice to three hundred times by inserting high impurity concentration region under the source drain contact area. The cause of the inferior characteristics of conventional devices is attributed to the deficiency of carriers in the channel region, resulting to a very high potential drop at the source-channel interface. These results should pave the way to very high performance OTFT devices.

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The collection of injected electrons for dye-sensitized solar cells (DSSCs) was improved by two studies of three dimensional fluorine doped SnO₂ transparent electrodes (3D FTO). One of the studies conducted here involved making textured glass substrates of silica sphere particles and low resistance FTO films. The other study involved a transparent 3D FTO electrode incorporated into the porous titania layer. In order to suppress back reactions between I₃^- ions and FTO, the FTO film surfaces in the DSSCs had to be covered with compact titania films prepared by using titanyl nitrate solutions. We confirmed the time constants for the recombination and collection of the injected electrons by using optical modulation techniques. It was found that these 3D configurations contributed to the improvement in the performance of the DSSCs.

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Poly(3-octylthiophene)/polymethylmethacrylate (P3OT/PMMA) composite thin films were prepared by spin coating as composing a prism-coupling waveguide. The optical absorption property of the composite thin film was evaluated using UV-visible spectra in the range 300-900 nm. The optical bistable characteristics of the prism-coupling waveguide composed of P3OT/PMMA composite film was measured for different input laser power intensities using optical bistable measuring equipment. The optical bistability of the waveguide was measured using a Nd:YAG laser with a wavelength of 1,064 nm, pulse width of 5 ns and a repetition frequency of 10 Hz. The optical bistable characteristics of P3OT/PMMA composite waveguides for different input power intensities shows good stability and hysteresis characteristics. However, in terms of the input laser power dependence of optical bistability, the switching on-off position shifts with the increase in input power intensity. In addition, the effect of organic gas treatment and PMMA molecular weight on the optical bistable characteristics of P3OT/PMMA composite waveguides was investigated.

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Vanadyl phthalocyanine (VOPc) thin films are fabricated using molecular beam epitaxy (MBE) technique on KBr (001) substrate preheated at different temperatures under vacuum. VOPc thin films on the KBr substrate cleaved in air and then preheated in vacuum are investigated using scanning electron microscopy (SEM) images and UV-vis absorption spectra. VOPc thin films depend upon preheating temperature of KBr substrate. Large VOPc grains appear in the background of small crystals on the substrate preheated at low temperatures, while more small grains appear on the substrate preheated at higher temperatures and the film is smoothly and epitaxially grown. The preheating at high temperatures removes adsorbed gasses from the substrate. The effecs of preheating indicate that gas molecules adsorbed on the KBr substrate strongly affect the morphology of the VOPc thin film. The third-order nonlinear optical susceptibilities χ⁽³⁾ (-3ω; ω, ω, ω) of the epitaxial and pseudomorphic VOPc films were determined using the Maker fringe technique.

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Vapor deposition polymerization(VDP) have been utilized for producing polymeric thin films, such as polyimides, polyamides, and polyureas by co-evaporation of two types of bifunctional monomers onto the substrate surface. Through the use of poling treatment, polyureas acquire pyroelectric and piezoelectric activities comparable to those of PVDF. In this study, polyurea thin films were prepared by vapor deposition polymerization. The ordered structures and physical properties were investigated by means of infrared spectroscopy. The infrared spectra indicate that the dipoles of urea groups in the polymer were oriented normal to the surface of substrate. This results that strong interaction between the substrate interface and the urea groups results in the orientation of the urea dipoles during annealing. Moreover, the introduction of aliphatic moieties into the polymer main chain gives rise to easy thermal reorientation of the dipoles in comparison with aromatic moieties. In comparison with aromatic moieties which have rigid frame structure need poling treatment to dipoles reorientation.

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In this study, we report on the evaluation of tilt angles of liquid crystal (LC) molecules near the surface of SiO₂ alignment layers and in the whole cell when constant voltages are applied. A LC molecule, 4-cyano-4'n-pentylbiphenyl, was used in this study. The LC cell consisted of Au (50nm) / SiO₂ (30nm) /LC (3 μm)/ SiO₂ (30nm) / Au (100nm) system. SiO₂ alignment layers were obliquely evaporated on both Au surfaces. Surface plasmon resonance and guided waveguide excitation modes in attenuated total reflection configuration were used to monitor the alignment property of LC molecules adjacent to the surface and the bulk in the LC cell. In the ATR angular scan properties, the theoretical fittings agreed well with the experimental data on the assumption of simplified 5 LC layers model. The profile of the tilt angles from the surface to inside the cells was obtained by the theoretical fitting. In comparison with the internal bulk region, LC molecules near the surface required higher voltages to change their tilt angles toward vertical direction. As demonstrated in this report, this technique should provide the useful information to understand the interfacial phenomena for LC displays.

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Physical vapor deposition (PVD) is extensively used for preparing functional organic thin films. Detailed studies of thin film formation during PVD process are therefore demanded for improving the performance of organic thin film devices. In this study, the deposition behavior of evaporated molecules was observed in real time using a quartz crystal microbalance (QCM) and the time evolution curve for the initial stage of organic thin film formation on a quartz crystal substrate was compared to a theoretical curve using a rate equation based on a physisorption model. From the observation of deposition behavior using a QCM, it was demonstrated that the growth kinetics for organic thin films is dependent on the substrate temperature and the nature of substrate. Moreover, our proposed rate equation for the early stage of the film formation well reflected experimental results, and as a fitting parameter, the mean stay time on the substrate of deposited molecules was estimated from the fitting of the theoretical equation to the experimental results.

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Fullerene (C₆₀)-based n-channel field effect transistors (FETs) have been fabricated on various polymeric gate insulators as an alternative to conventional oxide gate insulators. The field effect mobility was improved to higher than 0.1cm²/Vs using proper gate insulator and by the heat-treatment in a vacuum, which was aimed for oxygen de-doping. The C₆₀ films deposited on polymer gate insulator at room temperature become amorphous even after the heat-treatment. However, the field effect mobility of C₆₀ films markedly depended on the polymer gate insulator materials, and it was attributed to the wettability of C₆₀ on polymer and the surface roughness on gate insulators. The very high field effect mobility of as high as 0.48cm²/Vs was successfully obtained when C₆₀ was deposited on aromatic hydroxyl-free polymer gate insulator (Cyclotene^TM, BCB) film.

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We attempt to control a chirality of a single-walled nanotube (SWNT) using free electron laser (FEL) irradiation during its growth. It is expected that the FEL irradiation with a wavelength corresponding to an optical absorption of SWNT with a specific chirality promotes the growth of the specific SWNT. The specific SWNT reveals an optical absorption corresponding to the each own chirality. CNTs were grown using alcohol catalytic chemical vapor deposition (ACCVD) method with ethanol. The FEL was in-situ irradiated during ACCVD. The FEL used in this work is featured by the variable wavelength and the very sharp pulse width approximately 500 ps. The FEL with the wavelength of 1300 ∼ 1450 nm was irradiated to grow semiconductive SWNTs with the diameter of ca. 1.1 nm. In the SWNTs grown without FEL irradiation and/or with 1350 nm FEL irradiation, radial breathing modes (RBM) peaks were observed. From the RBM peak value the diameter of the SWNTs was estimated ca. 1.1 nm. Also those SWNTs were thought to be metallic from Kataura plot and resonance Raman effects. On the other hand, it was confirmed that 1300, 1400 and 1450 nm FEL irradiations resulted in the change of SWNT chilality, where no RBM peak appeared.

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The electrical conductivity of a bulky polythiophene or a bulky gold has high value. If the electrical conductivity of nanometer scale films of polythiophene or gold has high value, it is very interesting that the molecular devices are combined with these polythiophene. The Langmuir-Blodgett (LB) films were synthesized from poly(3-hexylthiophene) (P3HT), and the LB films of P3HT were doped by the electrochemical method in present study. Samples of Al/P3HT LB films/Au generated the voltage. The time dependence of the voltage generated from the Al/P3HT LB films/Au was measured. The electrochemical doping caused the generated voltage of the samples to increase.

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A new method for increasing conductivity of π-conjugated polymer was demonstrated with a large amount of ionic salts. A π-conjugated polymer, poly (3,4-ethylenedioxythiophene) / poly(styrenesulfonate), as known PEDOT / PSS was mixed with lithium salts, such as EMI-TFSI, LiTFSI, and LiBETI. In particular, the mixture including 50 wt.% LiBETI showed a high conductivity, 75 S / cm.

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We fabricated electrospun poly (vinylalcohol) (PVA) fibers using a copper wire electrode in Teflon capillary tube, and the SEM images were observed. The apparatus in this method is reasonable, and needed volume of polymer solution and distance between the electrodes can be largely reduced compared to conventional method. The wire electrode tip position in the capillary tube is also important in this method and should be close to the polymer solution surface.

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We have investigated the thermal endurance and electrical insulating properties and mechanical properties of PDMS-based hybrid materials made from ethoxy-terminated PDMS and various metal alkoxides for application as electrical insulating encapsulants. The materials exhibited good thermal stability and good electrical insulating properties. The amount of all dimethyl cyclic siloxanes evaporated at 200°C from PDMS based hybrid were found to be much lower than silicone rubber.

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