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Xanthine oxidase (XO), a potent inducer of reactive oxygen species, catalyzes purine metabolism. XO is expected to be implication of the macrophage activation. XO is also expressed in the peripheral nerve system, while its role in diabetic polyneuropathy (DPN) has not been clarified. We explored the implication of XO in DPN of db/db mice (db/db) treating with XO-inhibitor, topiloxostat (To). C57BL6 mice (C57) and db/db (5 wks of age) were daily treated with 1mg/kg (dbT1) and 2mg/kg (dbT2) To (per os) for 8 wks. During experimental period, peripheral nerve function was monitored. At end, serum and dissected sciatic nerves and dorsal root ganglia (DRG) served for evaluation of uric acid metabolism. Primary culture of DRG neuron was performed to evaluate the effects of To on neurite outgrowth in vitro. To improved significant delay of nerve conduction velocities and elevation of threshold for tail flick test in db/db in a dose dependent manner (p As a conclusion, increase in XO activity in serum and DRG may be implicated in the pathophysiology of DPN in db/db. Activation of XO in serum may directly exacerbate neuronal injury for DRG in DPN. To has a beneficial effect on DPN through its specific property to suppress serum XO activity. Disclosure H. Ichinohe: None. H. Mizukami: None. S. Osonoi: None. K. Kudo: None. S. Yagihashi: None.

Purpose: Small fiber dysfunction is common in subjects with diabetic polyneuropathy (DPN). It is unsettled, however, whether marginal glucose intolerance is implicated in the onset and progression of small fiber dysfunction. Herein, we explored the relationship between glycated hemoglobin levels (HbA1c) and pain sensation in the Japanese population.Methods: A population-based study of 894 individuals (352 men, 542 women; average age 53.8 ± 0.5 years) and 55 subjects with impaired fasting glucose (IFG) in the 2017 Iwaki project were enrolled in this study. Individuals with diabetes were excluded. Relationships between pain threshold for intraepidermal electrical stimulation (P-IES) and parameters associated with metabolic syndrome were examined.Results: P-IES was elevated with increasing of age in women but not in men. Average P-IES (mA) was increased in IFG subjects (n = 55, 0.20 ± 0.03) compared with normoglycemic/non-IFG individuals (n = 894, 0.15 ± 0.01) (p < 0.01). It was comparable between IFG and a group of normal high HbA1c (5.9–6.4%). Univariate linear regression analyses showed no influence of sex, triglyceride, or cholesterol on the value of P-IES. In contrast, there were significant correlations between P-IES and serum HbA1c level (ß = 0.120, p < 0.001) Adjustments for the multiple clinical measurements confirmed positive correlation of P-IES with HbA1c (ß = 0.077, p = 0.046).Conclusion: Individuals with normal high HbA1c exhibited an elevated P-IES in a healthy Japanese population which may be useful for the screening of subclinical DPN.

Colorectal cancer is one of the most malignant neoplasms worldwide. Fucoxanthin is a carotenoid present in the chloroplasts of brown seaweeds. In the present study, the anticancer effects of fucoxanthin and its metabolite, fucoxanthinol, on 6 colorectal cancer cell lines and 20 tissue samples from surgically resected clinical colorectal cancer specimens were examined using a collagen-gel droplet embedded culture drug sensitivity test (CD-DST). The in vitro sensitivity to fucoxanthin, fucoxanthinol and the anticancer drugs is expressed as T/C (%), where T is the absorbance of cells which stained by neutral red treated with carotenoids and C is the absorbance of non-staining cells. Fucoxanthin and fucoxanthinol decreased the T/C (%) of Caco-2, WiDr, HCT116, and DLD-1 cell lines at doses of 20 µM. Fucoxanthinol also decreased the T/C (%) of SW620 cells, while the T/C (%) of Colo205 cells was not reduced by treatment with either carotenoid. Specifically, the T/C (%) of Caco-2 and WiDr cells, which were incubated in carotenoid-free medium for 6 days following treatment with 20 µM fucoxanthinol for 24 h, was markedly decreased to 1.4±0.2 and 12.0±0.3%, respectively. Furthermore, fucoxanthin and fucoxanthinol decreased the T/C (%) in colorectal cancer tissue samples. Notably, 20 µM fucoxanthinol treatment resulted in a higher proportion of colorectal cancer samples with a T/C (%) of

Innovative sensing systems based on THz electromagnetic waves have been attracting a great deal of attention. Although many THz detectors have been developed over the years, it is currently difficult to manufacture low-cost THz sensing/imaging devices. In the present study, we propose to use organic field-effect transistors (OFETs) and small potential fluctuation against the carriers within them (N. Ohashi, H. Tomii, R. Matsubara, M. Sakai, K. Kudo, M. Nakamura, Appl. Phys. Lett. 91 (2007) 162105). We use THz time-domain spectroscopy for OFETs in which the carrier density in the pentacene active layer is modulated by the gate bias. We found evidence that the accumulated free holes in pentacene films can be excited by THz photons to overcome the surrounding barriers in the fluctuating potential. The Drude–Lorentz model could not account for the shape of the absorption spectra, which suggests that the holes are weakly restricted by the potential fluctuation. The integrated absorption intensity was proportional to the transfer characteristics of the OFETs. The present findings represent an important step toward developing a new class of THz-wave sensors.

We controlled the in-plane orientation of pentacene grains by graphoepitaxy using patterned amorphous-SiO2/Si substrates on which periodic grooves with slope edges had been formed. Pentacene crystals exhibited a clear tendency to align their b-axes perpendicular to the groove edges. Organic thin-film transistors were fabricated on the patterned and flat substrates and their transistor characteristics were compared. Although the patterned substrates increased the apparent mobility by only 10–20%, the number of grain boundaries with high potential barriers to carrier transport was reduced to half of that on flat substrates. This improvement is expected to enhance the response speed of pentacene organic thin-film transistors and suppress the sensitivity of their characteristics to the operating temperature.

To clarify relationship between crystallographic and electronic structures in pentacene polycrystalline films grown on SiO2, in-plane crystallite size and random strain of the films were analyzed by grazing incidence X-ray diffraction (GIXD) using synchrotron radiation source. The results indicate that the diffraction peak width is not determined by random strain but by crystallite size. The crystallite size remains constant within the range of 25–50 nm even when the size of polycrystalline domain, or crystal grain, increases more than tenfold by elevating the growth temperature. The crystallite size agrees well with characteristic periods of both HOMO-band-edge fluctuations in pentacene films, which was reported in our previous paper, and surface corrugation of the substrate. These facts strongly suggest that roughness of the SiO2 surface limits the crystallite size and the interruption of long-range order in pentacene lattice introduces the HOMO-band-edge fluctuation.

We have demonstrated the inverter operation of stacked-structure CMOS devices using pentacene and ZnO as active layers. The fabrication process of the device is as follows: A top-gate-type ZnO thin-film transistor (TFT), working as an n-channel transistor, was formed on a glass substrate. Then, a bottom-gate-type pentacene TFT, as a p-channel transistor, was fabricated on top of the ZnO TFT while sharing a common gate electrode. For both TFTs, solution-processed silicone-resin layers were used as gate dielectrics. The stacked-structure CMOS has several advantages, for example, easy patterning of active material, compact device area per stage and short interconnection length, as compared with the planar configuration in a conventional CMOS circuit.

Extrinsic factors to disturb the carrier transport in pentacene field-effect transistors (FETs), as a representative of the high-mobility organic FETs (OFETs), have been comprehensively analyzed by using atomic-force-microscope potentiometry (AFMP), microscopic four-point-probe field-effect transistor (MFPP-FET) measurement, and other techniques. In the first part, by mainly using AFMP as a powerful tool to reveal the potential distribution in working OFETs, we show how and how much the formation of source/drain electrodes influences the apparent field-effect mobility both for top- and bottom-contact configurations. In the second part, we show the influence of irregular grain structures and regular grain boundaries. The films grown both at very low and high temperature ranges contain distinctive insulating parts, which make the apparent mobility very low. Within the moderate growth temperature range, the intrinsic field-effect mobility obtained by MFPP-FET measurement is proportional to the average grain size. This behavior is well explained by the polycrystalline model with the diffusion theory. According to the observations in this work, it is obvious that these extrinsic limiting factors must be carefully excluded to discuss the intrinsic mechanism of the carrier transport in OFETs.

Vertical electrical conduction in Au/(polycrystal-line pentacene)/Al diode structures and the influence of the kinetic energy of incident Au atoms on the conduction property have been comprehensively studied using current–voltage–temperature (I–V–T) measurements, ultraviolet photoelectron spectroscopy (UPS), atomic-force-microscope (AFM) current imaging, etc. In the I–V characteristics, a symmetrical ohmic current component appeared when a low voltage was applied, and a super-linear one appeared when a high positive voltage was applied to Au. The component in the high-forward-voltage region was concluded to be a thermionic emission of holes from Au with a 0.23-eV injection barrier, which is the normal hole conduction through the highest occupied molecular orbital of pentacene. On the other hand, the ohmic component was concluded to be a metal-like electron transport through high-density gap states at grain boundaries which were induced by the Au penetration into pentacene. UPS and I–V–T measurements clearly indicated the generation of the gap states and the enhancement of their density by the reduction of Au kinetic energy. For vertical-type devices with polycrystalline organic films, the ohmic conduction through the grain boundary will increase the leakage current. On the contrary, it possibly enhances the carrier injection in lateral-type transistors in the case of top-contact configuration.

We fabricated both thin film transistors (TFTs) and diodes using zinc oxide (ZnO) and pentacene, and investigated their basic characteristics. We found that field-effect mobility is influenced by the interface state between the semiconductor and dielectric layers. Furthermore, the complementary metal oxide semiconductor (CMOS) inverter using a p-channel pentacene field-effect transistor (FET) and an n-channel ZnO FET showed a relatively high voltage gain (8 - 12) by optimizing the device structure. The hybrid complementary inverters described here are expected for application in flexible displays, radio frequency identification cards (RFID) tags, and others.

We report two types of integrated circuits based on a pentacene static-induction transistor (SIT), a pentacene thin-film transistor (TFT) and a zinc oxide (ZnO) TFT. The operating characteristics of a p-p inverter using pentacene SITs and a complementary inverter using a p-channel pentacene TFT and an n-channel ZnO TFT are described. The basic operation of logic circuits at a low voltage was achieved for the first time using the pentacene SIT inverter and complementary circuits with hybrid inorganic and organic materials. Furthermore, we describe the electrical properties of the ZnO films depending on sputtering conditions, and the complementary circuits using ZnO and pentacene TFTs.

For the realization of high-performance organic static induction transistors (OSITs), it is important to investigate the effect of a hole injection barrier at the interface between a pentacene films and a source electrode in OSITs. In this study, the OSITs based on pentacene films were fabricated on various metallic source electrodes with different work functions and on copper phthalocyanine (CuPc)/indium tin oxide (ITO) electrodes with different CuPc thicknesses. The hole injection barrier was affected by the work function of metallic source electrodes (ITO, Au, and Pt) and the thickness of CuPc (0, 3, and 5 nm). The obtained results demonstrate that a high on/off ratio is achieved when a hole injection barrier with a moderate height is formed at the interface. It was found that controlling the hole injection barrier is effective for improving the characteristics of OSITs.

Organic thin-film transistors (OTFTs) are emerging as aninexpensive alternative to amorphous silicon devices becauseof their many attractive features, such as a simple fabricationprocess, low cost, and mechanical flexibility. Recently, the per-formance of OTFTs has been significantly improved by modi-fying the dielectric surface and/or source and drain (S/D) elec-trodes

For the better performance of organic thin-film transistors (TFTs), gate-insulator surface treatments are often applied. However, the origin of mobility increase has not been well understood because mobility-limiting factors have not been compared quantitatively. In this work, we clarify the influence of gate-insulator surface treatments in pentacene thin-film transistors on the limiting factors of mobility, i.e., size of crystal-growth domain, crystallite size, HOMO-band-edge fluctuation, and carrier transport barrier at domain boundary. We quantitatively investigated these factors for pentacene TFTs with bare, hexamethyldisilazane-treated, and polyimide-coated SiO2 layers as gate dielectrics. By applying these surface treatments, size of crystal-growth domain increases but both crystallite size and HOMO-band-edge fluctuation remain unchanged. Analyzing the experimental results, we also show that the barrier height at the boundary between crystal-growth domains is not sensitive to the treatments. The res...

Conventional organic static induction transistors (OSITs) have been directly fabricated on a source electrode formed on a substrate without the investigation of the effect of a surface treatment on device characteristics. We have fabricated the OSITs based on pentacene thin film with an ultrathin copper phthalocyanine (CuPc) layer. The influence of depositing this ultrathin CuPc layer on the source electrode on static characteristics was investigated. The obtained results provided an important fact indicating that a high on/off ratio of 230 and a high current of 3 µA in an organic SIT are achieved by the formation of a hole injection barrier that works as a tunneling layer on a source electrode. The barrier effectively controls the tunnel current from the source electrode by applying a gate voltage.

We have fabricated the organic conductive wires and nano-transistors using co-evaporation method of tetrathiafulvalene (TTF) and tetracyanoquinodimethane (TCNQ) under AC electric field. Needle-like crystals of TTF-TCNQ charge transfer complex grow from an edge of gold electrodes along the electric field. The frequency dependence of the growth time of molecular wires indicates that AC electric field around 100 Hz is the most effective for making connected wires. Many connected wires were highly conductive which did not show any modulation of electrical conductivity with the gate voltage. However N-channel field effect transistor characteristics were observed with improvements of growth sequence. It is suggested that a tiny semiconductor area is formed at the connecting point of two conductive molecular wires.

Grain morphology, crystal structure and transistor characteristics of pentacene films have been studied using molecular beam deposition under various conditions: growth temperature ranging from 5t o 80jC and growth rate from 0.15 to 2 nm/min. Grain morphologies observed with atomic force microscopy are categorized into five groups, which are summarized in a phase diagram. Above the growth temperature of 40 jC, many ‘recessed regions’ which extend independently of molecular steps are observed on the film surfaces. Carrier mobilities of the films estimated from transistor measurements are distributed from 110 5 to 0.20 cm 2 /Vs. A comparative study between the structural and electrical results indicates that the mobility does not explicitly depend either on grain size or on specific grain morphology. Lamellar grains associated with flat-lying molecules among differently oriented grains, gaps between grains and the recessed regions are considered to restrict the overall carrier mobility. D 2004 Elsevier B.V. All rights reserved.

Organic semiconductor transistors are expected for flexible displays, information tags, and the like. However, organic transistors have some disadvantages of current density and speed of operation, because of their high resistivity and low carrier mobility. To improve their performance, it is valuable to analyze the mechanism of operation. We have compared characteristics of lateral- and vertical-type transistors using pentacene evaporated films. The pentacene lateral-type FET characteristics showed large variation due to fabrication parameters such as deposition rate, substrate temperature, and film thickness. It was found that evaporated pentacene thin films have large grain gaps, which disturb carrier flow along the channel formed pentacene film/SiO2 interface direction and make FET characteristics unstable. It is assumed that pentacene films are not suitable lateral-type transistors. Accordingly, we have fabricated vertical-type organic static induction transistors (SITs) using pentacene evaporated films. The pentacene SITs show high-speed operation (cutoff frequency of 7.5 kHz) at relatively low voltages. Further optimization of SIT structure will improve the device performance. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 149(2): 43–48, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10500

We have fabricated tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) molecular wires between a parallel cathode and anode (100 µm electrode gap) using the co-evaporation technique with an applied electric field. Wire-shaped microcrystals of TTF-TCNQ grew along the electric field. We have succeeded in fabricating connected wires with an optimum applied voltage. A narrow-gap (20 µm) electrode was used to grow wires with a low applied voltage, which make it possible to fabricate the connected wires easily. The measured I-V curve indicated Ohmic contact between the gold electrode and TTF-TCNQ. Semiconductor-like conduction of the fabricated TTF-TCNQ sample was shown by the temperature dependence of conductivity. Some of the co-evaporated TTF-TCNQ wires may tend to be semiconducting due to nonstoichiometry of TTF1-δ-TCNQ1.

Highly oriented TTF-TCNQ grains were prepared by applying an electric field during the evaporation. We were able to clarify the orientation process of TTF-TCNQ grains and the electrical property corresponding to the long axis of the crystal grain.

We have fabricated photovoltaic cells using merocyanine and copper phthalocyanine dyes. The basic parameters, such as diffusion length of the photogenerated excitons, dielectric constant, and the carrier density in organic photovoltaic cells were estimated.

Copper phthalocyanine (CuPc) and merocyanine (MC) dyes show p-type semiconducting properties and have different absorption peaks in the visible spectral range. We fabricated new organic color sensors with the static induction transistor (SIT) structure using these dyes and investigated their photoelectric properties. The photocurrent from the source to the drain electrodes is controlled by the gate voltage and the pinch-off gate voltage is changed drastically by illumination. These phenomena can be explained in terms of the field-dependent and wavelength-dependent quantum efficiency in an organic SIT.

We have fabricated planar bottom-contact organic thin-film transistors as a function of the thickness of the pentacene active layer. The highest mobility of the planar bottom-contact transistors is 0.47 cm 2 /Vs with only a 7 nm pentacene active layer. Our planar bottom-contact transistors show much higher mobility than conventional bottom-contact counterparts and even higher than the reported mobility values of top-contact counterparts for each thickness in the range from 2.5 to 10 nm. We find that spike at the edges of source and drain electrodes seriously deteriorates device performance.

We have investigated the effect of bias voltage applied to an electrically conductive substrate on the formation of adsorption Langmuir–Blodgett (LB) films. In fabricating the adsorption LB films, we used tetracyanoquinodimethane (TCNQ) with a long alkyl chain as a molecule for spreading monolayers on the subphase and tetramethyl- p -phenylenediamine (TMPD) as a material for adsorbing from the subphase to the monolayers. It is well known that TCNQ and TMPD are acceptor-like and donor-like molecules, respectively. In the visible absorption spectra and Fourier transform infrared reflection–absorption spectra of the adsorption LB films fabricated under several bias conditions, the peaks assigned to TCNQ show a clear dependence on the bias voltage. The electrical conductivity corresponding to the quantity of charge-transfer complex was also obtained. These results demonstrate that the bias-voltage LB technique enables us to control the formation of the charge-transfer complex.

Negative photoelectrical properties are observed in adsorption Langmuir–Blodgett films consisting of merocyanine dye and brilliant green under illumination using two lights. These peculiar properties are strongly dependent on the polarized direction of the two lights and their wavelengths corresponding to the absorption peaks of the two dyes. We have analyzed the photoelectric process between the two dyes, comparing the experimental results and the simulation using the model for photogenerated carriers via trap levels formed between the two dyes.

Langmuir-Blodgett (LB) films containing functional dyes were deposited directly onto optical fibers by the adsorption LB method. A merocyanine derivative having a long alkyl chain and rhodamine B were used as spreading and adsorbing molecules from the aqueous subphase, respectively. During the LB film deposition, absorption spectra from the optical interaction with the LB films at the core portion of the fiber were monitored using a multi-channel photo-detector system. Furthermore, the influence of the excitation light, which was guided into the fiber during the deposition, on the film deposition was investigated. The experimental results indicated that the in-situ optical measurement using optical fibers has high sensitivity and this is one of the promising methods to investigate the molecular interactions and the effect of the incident light on the LB film deposition.

Absorption spectra of adsorption Langmuir-Blodgett (LB) films were measured during and after the deposition of malachite green adsorbed merocyanine LB films on an optical fiber. The experimental results show that the in-situ optical monitoring using optical fibers is one of the powerful method to investigate the optical properties and the molecular interactions in the adsorption LB films.

We have investigated thermal oxidation of silicon, and dry and wet etching characteristics of the oxide layer after N+ (Ar−) ion implantation and subsequent annealing. An oxidation resistance is observed in the N+ implanted silicon with doses more than 1 × 1015 N+ /cm2. The etch rate of the oxide layer in a diluted HF solution is enhanced with a dose of 1 × 1015 N+ / cm2, whereas an etching resistance is observed for the samples with doses more than 2 × 1015 N+ /cm2. However, only the etching resistance appears in the dry etching. These resistances are also observed by argon implantation and easily removed by subsequent annealing. These results indicate that the oxidation and etching resistances are related to a thin oxynitride formation and the surface modification by ion implantation.

The formation of carbon clusters in ion implanted organic films was examined by electrical conductivity and optical absorption measurements. The surface resistivity of the films decreased by seven orders of magnitude after the ion implantation. The main optical absorption peaks of the film decreased gradually with increasing ion dose, and the absorption profile of the film was changed into a broad and monotonical one. Ion implanted polyethylene films had strong peaks at shorter wavelengths in the absorption spectrum. These results demonstrate that carbon clusters containing fullerenes (C60, C70) were created in organic films by ion implantation.

IR and inelastic electron tunneling spectroscopy (IETS) techniques are employed to investigate adsorption Langmuir-Blodgett monolayers deposited on silicon substrate with a thin SiO2 film. Merocyanine dye (MC) and crystal violet (CV) are used as a spreading material and an adsorption dye from an aqueous subphase, respectively. IR and IETS data show that the carboxyl group in the MC molecule and the substituent group in the CV molecule are concerned with the adsorption mechanism.

The effects of organic buffer layers consisting of Langmuir-Blodgett (LB) monolayers on the film growth of organic materials were investigated. Tetracyanoquinodimethane (TCNQ) was vacuum-evaporated onto the LB monolayers formed on silicon and glass substrates. The crystallinity and molecular orientation in the evaporated films were analyzed by using X-ray diffraction measurement. These results revealed that the organic buffer layer using LB films strongly affects the orientation of the TCNQ molecules, and the LB films are suitable materials to use for investigating the growth mechanism in relation to the interaction between evaporated molecules and the organic buffer layer.

We fabricated the photo-spectral sensitivity controllable cells with a multi-layered structure of organic dyes and investigated the photoelectrical properties. The photocurrent spectra of these cells shows high sensitivity in the visible spectral range, and the spectral sensitivity can be controlled by the bias voltage. These phenomena can be explained by the field-dependent and wavelength-dependent quantum efficiency of the organic dye layers.

Vertical type organic light emitting transistors (OLETs), which combined with the organic static induction transistors (OSITs) as the vertical type organic transistors and conventional organic light emitting diodes (OLEDs), are promising for flexible sheet displays. In our recent research, pentacene based OSITs fabricated on flexible plastic substrates exhibited stable electrical characteristics under bending condition. However, several problems have remained in the OSITs with low on/off ratio and low current value for use in the vertical type OLETs. This paper describes our recent efforts to improve the performance of vertical type OLETs by optimizing the device structure and organic materials used in the OSITs. Interface between organic source electrode and semiconductor is important factor to control the device operation of vertical type organic transistors. CuPc layer was inserted between ITO source electrode and pentacene film in order to improve the performance of OSITs. The results showed that both the high on/off ratio more than 103 and the high current value of larger than 40 μA were achieved. In addition, vertical type OLET and logic devices were fabricated using the OSITs for the realization of flexible sheet displays. These results exhibit that the OSITs attract attention for application in organic flexible displays.

Reactions of substituted acetone derivatives with acrylic acid esters (>200 mol %) in the presence of t-BuOK (200 mol %) in t-BuOH-THF (1:1 by volume) turned out to proceed as a cascade process consisting of the first Michael addition, the second Michael addition, and the last Claisen reaction to afford 4,4-disubstituted cyclohexane-1,3-diones. Only more substituted enolates play the role of a Michael donor in this cascade process, and therefore the ketone took up two alkoxycarbonylethyl groups on the same carbon bearing more substituents. Such intermediates were followed by intramolecular Claisen reactions leading to cyclohexane-1,3-diones bearing quaternary stereogenic centers at C(4), which bears an alkoxycarbonylethyl group and the substituent of the starting acetone derivatives. Thus-obtained 4,4-disubstituted cyclohexane-1,3-diones were successfully employed for total syntheses of intricate alkaloids of biological interest such as (+)-aspidospermidine, (±)-galanthamine, (±)-lycoramine, and (±)-mesem...

The electronic structure of pentacene/graphite, pentacene/Cu-phthalocyanine (CuPc)/graphite, and $\text{pentacene}∕\mathrm{Si}{\mathrm{O}}_{2}∕\mathrm{Si}(100)$ was studied by ultraviolet photoelectron spectroscopy as a function of the thickness of the pentacene film. We observed that the binding energy position of the highest occupied molecular orbital (HOMO) of pentacene becomes significantly lower on CuPc and $\mathrm{Si}{\mathrm{O}}_{2}$ surfaces than that on graphite. Furthermore, a splitting of the UPS band was observed only for the HOMO of thicker crystalline films on CuPc and $\mathrm{Si}{\mathrm{O}}_{2}$ surfaces, where the molecules are oriented with their long axis nearly perpendicular to the substrate surface. The splitting is ascribed to the intermolecular band dispersion, and the decrease in the threshold ionization energy on CuPc and $\mathrm{Si}{\mathrm{O}}_{2}$ surfaces originates from the HOMO-band dispersion as well as the increase in the relaxation/polarization energies, which may be caused by the better molecular packing structure with a nearly standing molecular orientation.

Organic static induction transistors (OSITs) with vertical structure have advantage of lower operational voltage compared to the organic field effect transistors with conventional lateral structure. In this study, OSITs based on pentacene films were applied to fabricate the organic inverters which can operate at low voltage. The experimental results demonstrate that organic inverters based on the OSITs show basic transfer characteristics and a low operational voltage of ±2 V.

Step-edge vertical-channel organic field-effect transistors (SVC-OFETs) with a very short channel have been fabricated by a novel electrospray deposition (ESD) method. ESD is the direct patterning process in which a solution is sprayed by using an electric field between the nozzle and electrodes formed on samples. The electrosprayed solution accumulates on the electrode pattern, and SVC-FETs based on 6,13-bis(triisopropyl-silylethynyl) pentacene (TIPS-pentacene) and a ZnO layer formed by ESD showed typical p- and n-channel FET characteristics, respectively. The results demonstrate that this ESD direct wet patterning is a useful method for complementary inverters and integrated circuit applications.

In-situ observations of vapor-phase growth of tetrathiafulvalene (TTF)-tetracyanoquinodimethane (TCNQ) crystals under an electric field were conducted without influencing the actual crystal growth process. The shortest incubation time of TTF-TCNQ nuclei and the highest initial growth rate of the crystals are obtained on the anode side and in high electric field regions. It is demonstrated that the distribution of molecules thermally diffusing on the substrate surface is controlled by an external electric field. These results indicate the potential for selective growth of highly conductive organic wires for micro- and nanoscale wiring in organic nanodevices.

Thermally stimulated current (TSC) and current-voltage measurements were carried out for Schottky diodes using pentacene thin films in order to investigate the relation between carrier traps and electrical conduction. Two type of TSC peaks originated from the traps at the metal-pentacene interface and in the depletion layer were observed. The current-voltage characteristics of the diodes were governed by the space charge limited conduction depending on these traps.

Ultrathin multilayered films of CuPcSAS and polyaniline were fabricated using spin-assembly method. The adsorption properties of the two materials were characterized and found to be of the as Langmuir type. The thickness of each layer was measured by AFM, and was consistent with the corresponding molecular size. These results indicated that the films could be fabricated with the self-assembly. The novel spin-assembly method is also applicable to this process. We also observed the film's electrical properties by making field-effect and conductivity measurements. It was found that the CuPcSAS monolayer was a semiconducting property, and that the conductivity of the multilayered films could be controlled over a wide range from insulating to highly conductive.

An organic complementary inverter which consists of a p-channel pentacene step-edge vertical channel organic field-effect transistor (SVC-OFET) and an n-channel hexadecafluorophthalocyanine (F16CuPc) SVC-OFET has been demonstrated. The two short-channel SVC-OFETs have been fabricated on the two steep side walls of a single gate line using a self-aligning technique. Such a structure significantly simplifies the layout and wiring of the inverter circuit. The inverter exhibited the same input and output swing ranges as the supply voltage, a logic threshold voltage very close to half of the supply voltage and a gain larger than 3.

Conductivity anisotropy in a crystal grain of thin-film-phase pentacene has been estimated by a combination of atomic-force-microscope potentiometry (AFMP) and electrostatic simulation. The surface potential distribution and topography of a grain in a working pentacene thin-film transistor are simultaneously measured by AFMP. Then, the nonlinear potential profile due to the thickness variation is simulated by changing the anisotropic ratio of conductivity. The anisotropic ratio (corresponding to the anisotropy of carrier drift mobility) is estimated to be σ x : σ z = 45 : 1 , where x is the horizontal (harmonic mean of those in a - and b -axes) direction and z is the vertical ( c -axis) direction.