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.

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The Maxwell-Wagner type interfacial charging processes were characterized by time-resolved second harmonic generation method (TR-SHG) using three typical organic double-layer devices, i.e., IZO/α-NPD/Alq3/Al for OLED and ITO/PI/α-NPD (or pentacene)/Au for MIM elements. Devices with a PI blocking layer represent one-carrier transport case, while the OLED is a typical two-carrier transport device. It is found that three devices show similar behavior of charging of the electrodes, however, interfacial charging behavior was different from case to case. On the basis of Maxwell-Wagner model, the different transients were analyzed with consideration of carrier species responsible for the interfacial charging. The observed TR-SHG well support the results of I-V measurements.

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We report a new approach to creating a ‘solid ink’ and direct patterning of InAs nanowires on a Si substrate using dip-pen nanolithography (DPN). The normal method to prepare an ‘ink’ is a solution-based process using sonication to liquidize nanoparticles, which we call ‘liquid ink’ in this paper. As ink-solution-based DPN patterning has been prevalent in most studies, herein we propose a new method, ‘solid inking’, by which the inking process is solution-free. In our work, InAs nanowires were transferred to an AFM tip by directly scanning the tip over an InAs nanowire wafer at humidity over 80%. By this method, the preparation of ink and the ‘inking’ process is combined into one step, and a large amount of nanowires can be collected onto the tip to ensure the formation of a continuous ink flow for the direct patterning.

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The purpose of this work is to synthesize a three-dimension C₆₀ polymer using photo-polymerization method. The used pristine materials were C₆₀ precipitates prepared by a liquid-liquid interfacial precipitation (LLIP) method. The prepared LLIP material was set in the vacuum and was compressed in the anvil with the pressure of 600MPa or 7GPa. The 4th harmonics FEL with the wavelength of 500nm was irradiated with macro-pulses (the pulse width of 20µs) containing very short micro-pulses (the pulse width of 200fs). The Raman Ag(2) peak of C₆₀ molecules in the vicinity of 1469cm^-1 becomes broad and shifts to the lower energy region as proceeding of polymerization. Under high pressure and/or FEL irradiation the LLIP crystal revealed the large red-shift and the increment of the half width of the Raman Ag(2) peak. Furthermore the LLIP crystal mixture with iodine revealed the more distinctive red-shift, ca. 13cm^-1 because of highly packing of C₆₀ molecules. The C₆₀ molecular accession by LLIP process and/or the photo-assisted hole-doping from iodine were promising conditions to promote the photo-polymerization effectively.

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Thin films of a divinyl derivative of tetraphenyldiaminobiphenyl DvTPD were prepared by vapor deposition followed by annealing. After annealing at 200°C for 1h, the film became practically insoluble to organic solvents due to polymerization. Electrical characteristics of the films were measured by current-voltage measurement, time-of-flight measurement, and dielectric measurement. It was found that the hole mobility of DvTPD decreases when the film is polymerized. As a consequence of the decrease of hole mobility, carrier balance in the emissive layer of an organic light emitting diode (OLED) was improved, leading to a higher quantum efficiency and a pure emission spectrum. The dielectric measurement also confirmed the high thermal stability of the polymerized film.

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Semiconducting polymers, poly(1,4-phenylene) (PPP) and poly(4-diphenylaminostyrene) (PDAS), which are soluble to organic solvents, were synthesized and were deposited by means of electrospray deposition (ESD). The ESD generated spherical shells of diameters ranging from a few to several tens of microns. The shells consisted of coagulation of nanometric particles of the semiconducting polymers. Formation of the shells was largely influenced by the concentration of spray solution. It was also found that the formation of shells can be achieved with various types of soluble polymers.

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In situ observation of the adsorption process and the states of cytochrome c on glass/solution interfaces, and the functionality of the reduction reaction of adsorbed cytochorome c were performed by using slab optical waveguide (SOWG) spectroscopy. The peak position of the absorption band of cytochorome c adsorbed on a bare glass surface was almost the same as that of that in solution. The cytochorome c adsorbed on glass/solution interface was reduced by sodium dithionite solution. The adsorbed cytochorome c was still maintained its functionality after immobilization.

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A two-dimensional microarray of ten thousand (100×100) hepatocyte hetero-spheroids, underlaid with non-parenchymal cells, was successfully constructed with a 100-µm spacing on micro-fabricated glass substrates that were coated with poly(ethylene glycol) (PEG). Co-cultivation of hepatocytes with endothelial cells was essential to stabilize hepatocyte viability and liver-specific functions, allowing us to obtain hepatocyte spheroids with a diameter of 100-µm, functioning as a miniaturized liver to secrete albumin for at least 1 month. The most important feature of this study is that these substrates are defined to provide an unprecedented control of substrate properties for modulating cell behavior, employing both surface engineering and synthetic polymer chemistry. The spheroid array constructed here is highly useful as a platform of tissue and cell-based biosensors (TBB and CBB), detecting a wide variety of clinically, pharmacologically, and toxicologically active compounds through a cellular physiological response.

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We investigated the photovoltaic properties of multi-layered devices consisting of ITO/oxide/Tetraphenyl porphyrin (H₂TPP)/Fullerene (C₆₀)/Bathocuproine (BCP)/Al structures. The V_OC markedly increases with the insertion of NiO and MoO₃ hole collection layers. However, the “kink” behaviors and temperature dependent properties are observed for the devices with and without MoO₃ especially for the thick H₂TPP film. We demonstrated the analysis of the photovoltaic properties using the Poole-Frenkel and Schottky models based on the dielectric behaviors of porphyrin and MoO₃ layers.

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By using electric field induced second harmonic generation (EFISHG) and Capacitance-Voltage (C-V) measurements, we studied carrier behaviors in ITO/polyimide (PI)/poly (3-hexylthiophene)(P3HT)/Au diodes. Photoillumination caused the threshold voltage shift in the C-V, and agreed well with the shift probed by the EFISHG. Results suggested trapped electrons were accumulated in the PI layer.

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A solution-processed red-sensitive organic photoconductive device was demonstrated by using soluble nickel-phthalocyanine. We found that a ratio of four nickel-phthalocyanine regioisomers was important factor for the high optical-electrical conversion efficiency. A maximum external quantum efficiency of device of 0.83% was achieved by optimizing the device structure.

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High luminance and high speed response with the cut-off frequency of more than 50MHz in multilayer polyfluorene-based light-emitting diodes with an interlayer were achieved. We realized multilayer polyfluorene-based light-emitting diodes for frequency response up to 100MHz.

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The nanoporosity installed in conjugated polymer films prepared by electrophoretic deposition makes it difficult to measure the amount of polymer deposited on a substrate. Here, an alternative approach, the estimation of material efficiency of the electrophoretic deposition from the optical absorption spectra of the residual suspensions has been studied. The ultimate recovery rate, which becomes smaller in suspensions with lower acetonitrile content, does not depend on the deposition voltage. The light scattering by the colloidal particles seems to be absent in residual suspensions after a deposition long enough to reach the ultimate recovery rate, indicating the exhaustion of the colloidal particles. Although the deposition rate of the polymer markedly lowers upon coating of the deposition electrode with PEDOT, the ultimate recovery rate remains unchanged. These results suggest that the material efficiency in this deposition method is limited by the generation rate of the colloidal particles in the suspension.

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A half-cylindrical BK-7 prism/dielectric film with a grating/Ag film/fluorescent polymer film structure was prepared, and its surface plasmon (SP) excitation property was investigated. It was confirmed experimentally that SP excitations are possible in this structure by using prism and grating couplings. The SP excitation property depended on the direction of the grating vector. Furthermore, intense photoluminescence was observed when the SPs were simultaneously excited at the Ag/polymer interface by prism coupling and at the Cytop/Ag interface by grating coupling.

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In this paper, the performance of the induced dimension reduction (IDR) method implemented along with the method of moments (MoM) is described. The MoM is based on a combined field integral equation for solving large-scale electromagnetic scattering problems involving conducting objects. The IDR method is one of Krylov subspace methods. This method was initially developed by Peter Sonneveld in 1979; it was subsequently generalized to the IDR(s) method. The method has recently attracted considerable attention in the field of computational physics. However, the performance of the IDR(s) has hardly been studied or practiced for electromagnetic wave problems. In this study, the performance of the IDR(s) is investigated and clarified by comparing the convergence property and memory requirement of the IDR(s) with those of other representative Krylov solvers such as biconjugate gradient (BiCG) methods and generalized minimal residual algorithm (GMRES). Numerical experiments reveal that the characteristics of the IDR(s) against the parameter s strongly depend on the geometry of the problem; in a problem with a complex geometry, s should be set to an adequately small value in order to avoid the “spurious convergence” which is a problem that the IDR(s) inherently holds. As for the convergence behavior, we observe that the IDR(s) has a better convergence ability than GPBiCG and GMRES(m) in a variety of problems with different complexities. Furthermore, we also confirm the IDR(s)'s inherent advantage in terms of the memory requirements over GMRES(m).

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We fabricated and evaluated a prototype imaging system using the Simultaneous Frequency-Encoding technique, which is an active imaging technique that is potentially capable of fast frame-frequency imaging using a frequency-scanning antenna with only a single transceiver. The prototype performed simultaneous acquisition of pixels in elevation using Simultaneous Frequency-Encoding and performed a mechanical scan in azimuth. We also studied a ranging technique and incorporated it into the prototype. The ranging technique for Simultaneous Frequency-Encoding must take into account the characteristics of the frequency-scanning antenna, which are fundamental to Simultaneous Frequency-Encoding. We verified that ordinary range processing can be performed before frequency analysis with Simultaneous Frequency-Encoding, giving both range and angular profiles. The prototype was evaluated based on the radiation patterns of a receiver antenna comprising the frequency-scanning antenna and a reflector, on which both the image quality and ranging performance depend. Finally we conducted actual imaging tests and confirmed the capability of through-obstacle imaging. The frame frequency was only 0.1Hz, which was due to the use of a slow mechanical scan in azimuth. However, assuming electronic beam forming is used instead of the mechanical scan, the frame frequency can be improved to several Hertz.

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In this article, a simple structure of the Wilkinson power divider which can suppress the nth harmonics of the Wilkinson power divider is proposed. By replacing the quarter wavelength transmission lines of the conventional Wilkinson power divider with the equivalent P-type transmission lines, a compact power divider which can suppress the nth harmonic is achieved. Design equations of proposed P-type line are achieved by ABCD matrices. To verify the design approach, the proposed power divider is designed, simulated (by ADS, CST Studio, and Sonnet simulators), and fabricated at 1GHz to suppress the fifth harmonic. The proposed structure is 46% of the conventional Wilkinson power divider, while maintaining the characteristics of the conventional Wilkinson power divider at the fundamental frequency. The insertion losses at the fifth harmonic are larger than 35dB. Furthermore, the second to seventh harmonic are suppressed by least 10dB. Here is an excellent agreement between simulated results and measured results.

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Careful inspection of efficiency in a DC-DC converter and its dependence on different parameters have been key concerns for power electronic specialists for a long time ago. Although extensive research has been done on the estimation of power loss for different components in a DC-DC converter separately, there isn't any comprehensive study regarding power loss analysis in a DC-DC converter. In this research, detailed description and necessary considerations in order to analyze the power loss of all components in a Push-Pull DC-DC converter are presented. Push-Pull topology is the best choice for investigating efficiency issues, since it exhibits all different types of power loss that are usually encountered in DC-DC converters. This research proposes and verifies appropriate power loss models for all components in a DC-DC converter that dissipate power. For this purpose, conduction and switching loss models of all the relevant components are fully developed. The related equations are implemented in MATLAB environment to simulate all possible causes of power loss in the converter. In order to provide a test bed for evaluation of the proposed loss models and the converter efficiency, a 50W Push-Pull DC-DC converter was designed and implemented. The experimental results are in full accordance with the simulation results in different input voltages, load conditions and switching frequencies. It was finally shown that the proposed models accurately estimate the DC-DC converter's efficiency.

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In this paper, closed-form analytical equations for the time-domain amplitude of the MOS cross-coupled oscillators are derived. The procedure of the paper is based on estimating an accurate equation for describing the behavior of the cross-coupled MOS configurations and finding a reasonable solution for the nonlinear differential equation governing the circuit. The solution method is presented for a general equation and is valid for all possible second-order oscillators. Both of the long channel and short channel transistor topologies have been investigated. The resulted equations are in a good agreement with simulation results for a wide range of the circuit parameters and enable us to analyze and synthesize the oscillators with the desired transient behavior.

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A CMOS detection procedure for ultra-wideband impulse radio (UWB-IR) communication system, employing Bi-Phase Shift Keying (BPSK) modulation scheme, is presented here. The chip was designed and fabricated in a 180nm CMOS process and it requires a supply voltage of 1.8V, with a die area of 0.01mm². A train of Gaussian Monocycle Pulses (GMP), modulated by a random data sequence of 1Gb/s, has been detected successfully by the detector. Ability to process differential data without using conventional blocks like mixer, correlator etc. while consuming a very low power (3.8pJ/bit for a data rate of 1Gb/s) is the novelty of this work. The detection scheme employing a simple architecture with a noncoherent detection mechanism is well suited for UWB-IR communication system.

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A broadband cruciform substrate integrated waveguide coupler is designed based on the planar circuit approach. The broadband property is obtained by widening the crossed region in the same way as rectangular waveguide cruciform couplers. As a result, a 3dB coupler with fractional bandwidth of 30% is realized at 24GHz.

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