bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhanced Scattered Light Imaging of Nanoparticles by Controlling the Polarization Distribution with Photonic Crystals
Authors: Otani Yuko , Urano Yuta , Honda Toshifumi , Watanabe Masahiro
Published: May 2013

An optical microscopy with a high sensitivity and resolution is required for observing semiconductor wafers and biological cells for nanotechnology and biotechnology applications. However, it is difficult to observe samples that are small compared with the optical wavelength since the signal is swamped by background noise such as dark noise and electrical noise and other signals besides that from the sample. Furthermore, light scattered from the sample cannot be focused into a spot in the image plane due to interference of polarized light, resulting in a blurred image that has a low resolution. This study proposes a method for removing the background noise and for improving the image resolution of nanoparticles by controlling the polarization direction. This method can be used to perform optical microscopy with a high sensitivity and resolution. We verify the effectiveness of this method by performing simulations and experiments. Simulations predict that the peak intensity obtained using this method will be 3.4 times higher than that obtained using a conventional microscope and that the resolution of this technique will be 0.43 times smaller than that of conventional microscopy. Experiments show that this method with a photonic crystal utilized as a radial polarization converter is capable of detecting 23-nm-diameter PSLs on a silicon wafer.
Effect of an Incoherent Glass Substrate on the Absorption Efficiency of Organic Solar Cells at Oblique Incidence Analyzed by the Transfer Matrix Method with a Glass Factor
Authors: Kang Kyungnam , Lee Sanghwa , Kim Jungho
Published: May 2013

We theoretically investigate the effect of the incoherent glass substrate on the absorption efficiency of organic solar cells (OSCs) at oblique incidence. The light propagation in the mixed incoherent glass substrate and coherent multilayer is calculated based on the transfer matrix method with a simple correction factor, which is derived at oblique incidence by taking multiple reflections inside the glass substrate. The validity of the proposed method is demonstrated by comparing the calculation results with those obtained by the generalized transfer matrix method. We investigate how the multiple reflections within the incoherent glass substrate affect the light absorption efficiency of thin-film OSCs, depending on the incidence angle and polarization.
ZnO/AlN Clad Waveguides for AlGaN-Based Quantum Cascade Lasers
Authors: Stattin Martin , Bengtsson Jörgen , Larsson Anders
Published: May 2013

Waveguide designs for AlGaN-based near-infrared quantum cascade lasers are proposed and analyzed using optical mode solvers. Because of the poor electrical conductivity, AlN is not a suitable cladding material for the AlN/GaN/AlGaN gain region. Instead we propose the use of ZnO as a conductive top cladding and to embed the gain region between AlGaN current injection and extraction regions so that an AlN substrate can be used as the lower cladding. We also examine the use of an AlN template on a SiC substrate and find that it can also provide sufficient mode confinement with negligible radiation loss into the SiC substrate. We identify a single mode ridge waveguide design with reasonable mode confinement (40%) and loss (39 cm-1).
Decomposition of Methylene Blue by using an Atmospheric Plasma Jet with Ar, N2, O2, or Air
Authors: Takemura Yuichiro , Yamaguchi Naohiro , Hara Tamio
Published: May 2013

We have performed experiments on the decomposition of methylene blue by using an atmospheric plasma jet with various working gases. The decomposition efficiencies of Ar, N2, and O2 plasmas are almost equivalent; on the other hand, the rate of methylene blue decomposition by air plasma is lower than those by the other plasmas. From the absorption spectra, it has been found that HONO (nitrous acid) is produced by air plasma-liquid reactions. It has been clarified by a series of experiments, where oxygen concentration in N2 plasma is varied, that the concentration of HONO increases and the rate of methylene blue decomposition degrades with increasing oxygen gas flow rate. Furthermore, the presence of nitrate ions and nitrite ions was confirmed by ion chromatography and pH measurement.
Development of Tool for Contamination Layer Thickness Measurement Using High Power Extreme Ultraviolet Light and in Situ Ellipsometer
Authors: Watanabe Takeo , Kikuchi Yukiko , Takahashi Toshiya , Katayama Kazuhiro , Takagi Isamu , Sugie Norihiko , Tanaka Hiroyuki , Shiobara Eishi , Inoue Soichi , Harada Tetsuo , Kinoshita Hiroo
Published: May 2013

Extreme ultraviolet (EUV) lithographic exposure is performed in a vacuum environment. The Mo/Si multilayers used as imaging optics and a mask can be contaminated by carbon, which is originally an outgassing species of the hydrocarbons that decompose from the resist materials during EUV exposure. This carbon contamination reduces the total reflectivity of the imaging optics and mask, and affects the lithographic performance, including the throughput and resist pattern replication resolution. This contamination should be reduced to maintain the lithographic performance; thus, the relationship between the carbon contamination and the outgassing species should be clarified. We therefore developed a novel tool for in situ contamination layer thickness evaluation. The distinctive features of this tool are as follows: 1) exposure using a total power of in-band EUV light (267 mW/cm2) that is as high as that required for high-volume manufacturing (>100 mW/cm2), 2) the visible light beam of the in situ spectroscopic ellipsometry is focused on the Mo/Si multilayer witness sample to obtain the detection limit for measured thickness and that the limit was found to be 0.03 nm, and 3) the witness and 8-in. resist wafer sample stages have extremely low outgassing characteristics. Using this tool, a starting adhesion point was observed and the carbon contamination layer thickness was evaluated during the resist exposure. For 90 min resist exposure, no contamination adhered onto the Mo/Si witness sample until the exposure time reached 25 min, and after which, the contamination started to adhere to the witness sample.
Dielectric and Insulating Properties of Embedded Capacitor for Flexible Electronics Prepared by Aerosol-Type Nanoparticle Deposition
Authors: Imanaka Yoshihiko , Amada Hideyuki , Kumasaka Fumiaki
Published: May 2013

The rapid evolution in electronic equipment has created a demand for advanced devices that are flexible, thin, and light in weight. This demand is driving the development of a core technology for flexible and stretchable electronic devices. To produce wearable computers, we need to fabricate functional membranes that contain passive devices, such as capacitors and resistors, on resin sheets at low temperatures. These sheets can then serve as mounting boards for various electronic devices. By improving the technique for room-temperature aerosol-type nanoparticle deposition of a ceramic material, we have established a technology for forming a dielectric inorganic BaTiO3 film with an excellent degree of crystallinity and favorable electric properties for use in the production of flexible and stretchable electronic devices on a polyimide sheet. By this method of forming a homogeneous nanoparticle structure inside a film, we produced a capacitor film with a dielectric constant of 200 on a polyimide sheet at room temperature.
Production of Highly Lubricious Ti-Based Ceramic Films for Reducing Friction between Web and Transiting Roller
Authors: Kohzaki Masao , Makita Ryohei
Published: May 2013

Web transiting process machines have been developed for producing flexible and printed electronics. For establishing a stable roll-to-roll transportation without web defects, the friction coefficient between the web and the transiting roller should be controlled at a low value. We produced the titanium nitride–molybdenum disulfide (TiN–MoS2) composite films by DC magnetron sputtering for improving the frictional characteristics of the transiting roller used in manufacturing process of flexible and printed electronics. The hardness of the TiN–MoS2 films was about 17 GPa at 22% MoS2. The composite films containing 22% MoS2 showed a low friction coefficient of approximately 0.1 at room temperature, which was almost equal to that of diamond-like carbon (DLC) films. In addition, only a small wear was detected on the films after the friction test. The adhesive strength of the composite films was improved by forming the Ti interlayer, and the further reduction of wear was observed.
Optoelectronic Properties of Nanostructured ZnO Thin Films Prepared on Glass and Transparent Flexible Clay Substrates by Hydrothermal Method
Authors: Venkatachalam Shanmugam , Hayashi Hiromichi , Ebina Takeo , Nakamura Takashi , Nanjo Hiroshi
Published: May 2013

In the present work, transparent flexible polymer-doped clay (P-clay) substrates were successfully prepared for flexible hybrid organic–inorganic light emitting diode (HyLED) applications. The thermogravimetric–differential thermal analysis (TG–DTA) curves showed that the thermal resistance of P-clay film was higher than that of plastic substrates. Then indium doped tin oxide (ITO) thin films were prepared on newly fabricated P-clay substrates by ion-beam sputter deposition (IBSD) method. The as-prepared ITO/P-clay samples were annealed at 220 °C for 1 h. The optical transparency and electrical conductivity of annealed ITO film on P-clay with smooth surface were better than that of P-clay with rough surface. ZnO seed layers were prepared on annealed ITO/P-clay, ITO/glass, and clay substrates by IBSD method. Surface morphology study showed that the ZnO seed layer coated ITO/P-clay substrate with smooth surface was very suitable for growing vertically aligned ZnO nanorod arrays. The structural study showed that the ZnO nanorod arrays grown by low-temperature solution growth method have good crystallinity and high purity. Optical study showed that the as-prepared ZnO nanorod arrays have excellent optical properties.
Memristive Behavior in Electrohydrodynamic Atomized Layers of Poly[2-methoxy-5-(2'-ethylhexyloxy)–(p-phenylenevinylene)] for Next Generation Printed Electronics
Authors: Awais Muhammad Naeem , Choi Kyung Hyun
Published: May 2013

Poly[2-methoxy-5-(2'-ethylhexyloxy)–(p-phenylenevinylene)] (MEH:PPV) based organic memristor (memory resistor) has been fabricated on the indium–tin oxide (ITO) coated poly(ethylene terepthalate) (PET) substrate by the electrohydrodynamic atomization (EHDA) technique. Thin jet containing MEH:PPV polymer was generated through a capillary under electrical stresses. The jet was broken into small droplets by adjusting the distance from nozzle to substrate and collected over the substrate under normal room conditions, consequently a high quality layer of MEH:PPV was achieved with an average thickness of 168 nm. The layer was morphologically characterized by a field emission scanning electron microscope (FESEM) analysis. X-ray photoelectron spectroscope (XPS) analysis was also carried out to confirm the chemistry of the deposited material. Electrically, ITO/MEH:PPV/Ag fabricated memristor was found to be switchable between high state and low state between ±4 V. The research work provides the memristive behavior in electrohydrodynamic atomized layers of MEH:PPV to be used for the next generation printed electronics application.
Phthalocyanine with Trifluoroethoxy Substituents for Organic Solar Cells
Authors: Yamada Ichiko , Iida Norihito , Hayashi Yasuhiko , Soga Tetsuo , Shibata Norio
Published: May 2013

The properties of soluble zinc phthalocyanines with trifluoroethoxy substituents (TFEO–ZnPcs) were studied to evaluate their possible use in organic thin-film solar cells. We prepared five TFEO–ZnPcs with different numbers and positions of the TFEO substituents. The solubilities, UV–visible absorption spectra, and cyclic voltammograms of these ZnPcs varied with their substituents. TFEO–ZnPc thin-films fabricated by spin-casting exhibited photocurrent generation at wavelengths between 600 and 850 nm. Flat heterojunction solar cells consisting of a poly(3-hexylthiophene) (P3HT) layer as a donor and a TFEO–ZnPc layer as an acceptor exhibited photocurrent generation over a wide range of wavelengths corresponding to both the P3HT and TFEO–ZnPc absorption spectra. The best solar cell performance was obtained with (β-TFEO)4ZnPc film.
Vertically Aligned ZnO Nanorods Grown by Low-Temperature Solution Processing
Authors: Lee Sunghee , Roy Biplab Kumar , Cho Junghyun
Published: May 2013

Zinc oxide (ZnO) films consisting of vertically aligned nanorods were hydrothermally grown on a seed layer at 90 °C using two precursors (zinc acetate, zinc nitrate). The microstructures and growth kinetics of ZnO films from various processing conditions were investigated to correlate to photovoltaic (PV) properties. For this, dye-sensitized solar cells (DSSCs) were assembled. Vertically grown nanorods exhibited the (002) out-of-plane texture and its size, alignment, density, and growth rate could be controlled by both solution and seed layer conditions. In particular, the stepwise deposition implemented by changing precursor solution every 2 h exhibited a higher power conversion efficiency (∼2.3% for 1.55-µm-thick ZnO film) than the continuous deposition. The zinc acetate seed layer cured as low as 100 °C enabled the templated growth of ZnO nanorods with an efficiency of ∼1.7% (for thickness of 1.4 µm). This will allow current low-temperature processing to be adopted for the fabrication of low-cost flexible PV devices.
Development of Film-on-Foil Ceramic Dielectrics for Embedded Capacitors for Power Inverters in Electric Drive Vehicles
Authors: Narayanan Uthamalingam , Liu Shanshan , Ma Beihai
Published: May 2013

Advanced power inverters for electric drive vehicles require capacitors that operate under high voltage at under-hood temperatures and have minimal footprint. This need can be realized by embedding ceramics with high dielectric constant within a printed wire board (PWB). The “film-on-foil” approach, where the high-dielectric-constant ceramic is first deposited on base-metal foil, is a promising method for embedding the capacitors within a PWB. We have deposited lead lanthanum zirconium titanate (PLZT) on nickel foils and characterized the samples in the temperature range between -50 and 250 °C. The measured dielectric constants varied with temperature: from ≈700 at -50 °C to ≈2200 at 250 °C. The dielectric loss remained fairly constant at ≈0.05–0.08. At 300 V bias, a dielectric constant of ≈110 and dielectric loss of ≈0.004 were measured. Hysteresis loop analysis showed an energy density of ≈85 J/cm3. The fabrication procedures and dielectric properties of the PLZT film-on-foils will be described in this paper.
Organic Electronic Devices with Copolymers Based on Naphthalene Diimide Connected with Non Conjugated Flexible Linker
Authors: Zhao Mingxiu , Hashimoto Kazuhito , Tajima Keisuke
Published: May 2013

The solid-state electronic properties of copolymers in which a naphthalene diimide derivative was connected with a non conjugated flexible linker were investigated. X-ray diffraction patterns of the polymer films show a π–π stacking peak, suggesting an intramolecularly folded structure in films. Organic thin-film transistors of the copolymer show n-type conduction with an electron mobility of 2×10-3 cm2 V-1 s-1. Bulk heterojunction-type organic photovoltaics in combination with poly(3-hexylthiophene) exhibited a power conversion efficiency of 0.22% under the illumination of AM 1.5 (100 mW cm-2).
Study on Optoelectronic Characteristics of Sn-Doped ZnO Thin Films on Poly(ethylene terephthalate) and Indium Tin Oxide/Poly(ethylene terephthalate) Flexible Substrates
Authors: Cheng Chi-Hwa , Chen Mi , Chiou Chin-Lung , Liu Xing-Yang , Weng Lin-Song , Koo Horng-Show
Published: May 2013

Transparent conductive oxides of Sn-doped ZnO (SZO) films with doping weight ratios of 2.0, 3.0, 4.0, and 5.0 wt % have been deposited on indium tin oxide (ITO)/poly(ethylene terephthalate) (PET) and PET flexible substrates at room temperature by pulsed laser deposition (PLD). Resultant films of SZO on ITO/PET and PET flexible substrates are amorphous in phase. It is found that undoped and SZO films on ITO/PET is anomalously better than films on PET in optical transmittance in the range of longer wavelength, possibly due to the refraction index difference between SZO, ITO films, and PET substrates, Burstein–Moss effect and optical interference of SZO/ITO bilayer films and substrate materials, and furthermore resulting in the decrement of reflection. The lowest electrical resistivity (ρ) of 4.0 wt % SZO films on flexible substrates of PET and ITO/PET are 3.8×10-2 and ρ= 1.2×10-2 Ω·cm, respectively. It is found that electrical and optical properties of the resultant films are greatly dependent on various amount of Sn element doping effect and substrate material characteristics.
Mechanical Integrity of Flexible In–Zn–Sn–O Film for Flexible Transparent Electrode
Authors: Kim Young Sung , Oh Se-In , Choa Sung-Hoon
Published: May 2013

The mechanical integrity of transparent In–Zn–Sn–O (IZTO) films is investigated using outer/inner bending, stretching, and twisting tests. Amorphous IZTO films are grown using a pulsed DC magnetron sputtering system with an IZTO target on a polyimide substrate at room temperature. Changes in the optical and electrical properties of IZTO films depend on the oxygen partial pressure applied during the film deposition process. In the case of 3% oxygen partial pressure, the IZTO films exhibit s resistivity of 8.3×10-4 Ω cm and an optical transmittance of 86%. The outer bending test shows that the critical bending radius decreases from 10 to 7.5 mm when the oxygen partial pressure is increased from 1 to 3%. The inner bending test reveals that the critical bending radius of all IZTO films is 3.5 mm regardless of oxygen partial pressure. The IZTO films also show excellent mechanical reliability in the bending fatigue tests of more than 10,000 cycles. In the uniaxial stretching tests, the electrical resistance of the IZTO film does not change until a strain of 2.4% is reached. The twisting tests demonstrate that the electrical resistance of IZTO films remains unchanged up to 25°. These results suggest that IZTO films have excellent mechanical durability and flexibility in comparison with already reported crystallized indium tin oxide (ITO) films.
Stretchable Circuits with Horseshoe Shaped Conductors Embedded in Elastic Polymers
Authors: Jahanshahi Amir , Gonzalez Mario , Brand Jeroen van den , Bossuyt Frederick , Vervust Thomas , Verplancke Rik , Vanfleteren Jan , Baets Johan De
Published: May 2013

Conformable electronics, i.e., electronics that can be applied on curved surfaces, is demanded nowadays in place of conventional rigid printed circuit board (PCB) based electronics for a number of applications. In the field of stretchable electronics there has been a swift progress in recent years. In this paper we are presenting our contribution to this ever growing topic, including thin-film based polyimide (PI), supported Au stretchable meanders as well as PCB based Cu meanders. These meanders are supported by PI or poly(ethylene naphthalate)/poly(ethylene terephthalate) (PEN/PET) films. Thin-film based stretchable interconnects is targeting mainly the biocompatible environments with demands for strong miniaturization while the PCB based technology is used more for large area applications. Both approaches are reviewed in this paper in terms of fabrication processes, materials and cyclic fatigue reliability. For each technology fabricated demonstrators are presented as well.
Solvent Effects on Solution-Processable Bulk Heterojunction Organic Solar Cells Utilizing 1,4,8,11,15,18,22,25-Octahexylphthalocyanine
Authors: Fukumura Kaoru , Hori Tetsuro , Masuda Tetsuya , Duy Dao Quang , Fujii Akihiko , Shimizu Yo , Ozaki Masanori
Published: May 2013

Bulk heterojunction organic solar cells utilizing soluble phthalocyanine derivative, 1,4,8,11,15,18,22,25-octahexylphthalocyanine (C6PcH2), have been fabricated by solution process with various solvents, and their photovoltaic properties have been studied. It is found that the marked differences on the morphologies of the bulk heterojunction film, such as the surface roughness, crystallinity and crystallite size, exist and relate with the boiling points of the solvents. The solvent effects on the photovoltaic properties have been discussed by taking the exciton dissociation efficiency and carrier transport efficiency into consideration.
Orientation of a Dip-Coated Bacteriorhodopsin Thin Film Studied by Second Harmonic Generation Interferometry
Authors: Yamada Toshiki , Haruyama Yoshihiro , Kasai Katsuyuki , Terui Toshifumi , Tanaka Shukichi , Kaji Takahiro , Kikuchi Hiroshi , Otomo Akira
Published: May 2013

We investigated the absolute orientation of bacteriorhodopsin (bR) thin film prepared by the dip-coating technique by means of second harmonic generation (SHG) interferometry. bRs in the bR thin films prepared in this technique tend to have a preference to orient with the cytoplasmic side away from the glass substrate and extracellular side toward the glass substrate. To assist in the analysis, the hyperpolarizability of covalently bound retinal chromophore was also evaluated by a computational calculation.
Study of Liquid Crystal Display Fabricated Using Slit Coater under Two Ultraviolet Irradiation Conditions
Authors: Ohtsuka Keisuke , Nagataki Yukihiro , Goda Kazuya , Oo Thet Naing , Miyashita Katsuyoshi , Hirata Hajime , Kimura Munehiro , Akahane Tadashi
Published: May 2013

We have recently reported on a method that utilizes a slit coater as a novel liquid crystal alignment technique. We carried out this study under two ultraviolet (UV) irradiation conditions, viz., (i) UV irradiation from the side of a glass substrate (exposure type 1) and (ii) UV irradiation from the side of the air–liquid crystal interface (exposure type 2), and investigated the electro-optical characteristics and azimuthal anchoring energy of liquid crystal sample cells performed under these two UV irradiation conditions.
Patterning Method for Silver Nanoparticle Electrodes in Fully Solution-Processed Organic Thin-Film Transistors Using Selectively Treated Hydrophilic and Hydrophobic Surfaces
Authors: Fukuda Kenjiro , Takeda Yasunori , Kobayashi Yu , Shimizu Masahiro , Sekine Tomohito , Kumaki Daisuke , Kurihara Masato , Sakamoto Masatomi , Tokito Shizuo
Published: May 2013

Fully solution-processed organic thin-film transistor (OTFT) devices have been fabricated with simple patterning process at a relatively low process temperature of 100 °C. In the patterning process, a hydrophobic amorphous fluoropolymer material, which was used as the gate dielectric layer and the underlying base layer, was treated with an oxygen plasma to selectively change its surface wetting properties from hydrophobic to hydrophilic. Silver source and drain electrodes were successfully formed in the treated areas with highly uniform line widths and without residues between the electrodes. Nonuniformities in the thickness of the silver electrodes originating from the “coffee-ring” effect were suppressed by optimizing the blend of solvents used with the silver nanoparticles, such that the printed electrodes are appropriate for bottom-gate OTFT devices. A fully solution-processed OTFT device using a polymer semiconductor material (PB16TTT) exhibited good electrical performance with no hysteresis in its transfer characteristics and with good linearity in its output characteristics. A relatively high carrier mobility of 0.14 cm2 V-1 s-1 and an on/off ratio of 1×105 were obtained with the fabricated TFT device.
Fabrication of 6,13-Bis(triisopropylsilylethynyl) Pentacene Films by Electrostatic Spray Deposition for Bottom-Contact Organic Field-Effect Transistors
Authors: Onojima Norio , Nishio Naomichi , Kato Takamasa
Published: May 2013

In this study, 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS pentacene) films were prepared by electrostatic spray deposition (ESD) for fabrication of bottom-contact organic field-effect transistors (OFETs) having the channel length of 5 µm. Since the crystalline quality of TIPS pentacene film strongly depends on the nature of the spray droplets, we investigated preparation condition of TIPS pentacene solution with mixed organic solvents. Large crystal domains were obtained by using a 1,2-diclorobenzene (o-DCB):ethanol mixed solvent. On the other hand, the film deposited using the toluene:ethanol mixed solvent was composed of small domains. Due to larger crystal domains obtained in the film deposited using the o-DCB:ethanol mixed solvent (i.e., reducing domain boundaries), we could fabricate the bottom-contact OFET exhibiting the field-effect mobility of 1.6×10-2 cm2/(V·s) which was almost 100 times higher than that based on the film deposited using the toluene:ethanol mixed solvent [2.0×10-4 cm2/(V·s)].
Direct Observation of Charge Carriers in Highly Magnesium-Doped Tris(8-hydroxyquinoline) Aluminum Thin Film by Electron Spin Resonance
Authors: Son Donghyun , Shimoi Yukihiro , Kizuka Tokushi , Marumoto Kazuhiro
Published: May 2013

We report on an electron spin resonance (ESR) study of a tris(8-hydroxyquinoline) aluminum (Alq3) thin film doped highly with Mg. We observed a clear ESR signal of radical anions in the film prepared by coevaporating Alq3 and Mg (Alq3:Mg= 1:3). The g value and peak-to-peak ESR linewidth ΔH
pp are obtained as 2.0030 and 2.24 mT, respectively, which coincide well with the reported values of an Alq3 thin film with a low Mg doping concentration. The spin susceptibility of the film was found to obey Curie's law, which indicates that no interaction exists between spins of Alq3 anions. The doped charges are found to be localized at deep trapping sites by lineshape analysis and from the temperature dependence of ΔH
pp. The doping concentration was evaluated to be 4.3%. This low doping concentration can be explained by the formation of Mg clusters in the film, which was directly confirmed by transmission electron microscopy.
Register Control of Roll-to-Roll Printing System Based on Statistical Approach
Authors: Kim Chung Hwan , You Ha-Il , Jo Jeongdai
Published: May 2013

One of the most important requirements when using roll-to-roll printing equipment for multilayer printing is register control. Because multilayer printing requires a printing accuracy of several microns to several tens of microns, depending on the devices and their sizes, precise register control is required. In general, the register errors vary with time, even for one revolution of the plate cylinder. Therefore, more information about the register errors in one revolution of the plate cylinder is required for more precise register control, which is achieved by using multiple register marks in a single revolution of the plate cylinder. By using a larger number of register marks, we can define the value of the register error as a statistical value rather than a single one. The register errors measured from an actual roll-to-roll printing system consist of a linearly varying term, a static offset term, and small fluctuations. The register errors resulting from the linearly varying term and the offset term are compensated for by the velocity and phase control of the plate cylinders, based on the calculated slope and offset of the register errors, which are obtained by the curve-fitting of the data set of register errors. We show that even with the slope and offset compensation of the register errors, a register control performance of within 20 µm can be achieved.
Fabrication of Polymer-Based Transistors with Carbon Nanotube Source Drain Electrodes Using Softlithography Techniques
Authors: Itoh Eiji , Kanai Ryo
Published: May 2013

In this study, we have developed the multilayer deposition and patterning processes with a resolution of 1 µm for fabricating polymer-based organic field effect transistors (p-OFETs) based on vacuum-free, solution processable softlithography techniques. We have used regioregular poly(3-hexylthiophene) (P3HT) as the soluble polymer semiconductor, and poly(methyl methacrylate) (PMMA) and polyimide as the soluble and insoluble polymer gate insulators, respectively. We have used multiwalled carbon nanotubes (MWNTs) as the printed source–drain (S–D) electrodes in order to fabricate vacuum-free, all printed OFETs. The p-OFETs with MWNT S–D electrodes exhibit higher hole mobility and on/off ratio than the devices with vacuum-evaporated Au electrodes, probably owing to the better contact of the electrode interface and damage-free transfer of electrodes onto the gate insulator. The mobility was further improved by the crystallization of the P3HT film after heat treatment prior to the pattern transfer of P3HT.
Comparison of Reactive Inkjet Printing and Reactive Sintering to Fabricate Metal Conductive Patterns
Authors: Kheawhom Soorathep , Foithong Kamolrat
Published: May 2013

Two methods to fabricate metal conductive patterns including reactive inkjet printing and reactive sintering were investigated. The silver printed lines were prepared from reactive inkjet printing of silver nitrate and L-ascorbic acid. Alternatively, the silver lines were prepared by the reactive sintering process of ethylene glycol vapor at 250 °C and formic acid vapor at 150 °C. In reactive printing, we investigated the effect of the number of printing cycles and the effect of silver nitrate concentration on the properties of the conductive patterns obtained. In reactive sintering, we investigated the usage of formic acid and ethylene glycol as reducing agents. The effect of reactive sintering time on the properties of the conductive patterns obtained was studied. As compared to reactive inkjet printing, the reactive sintering process gives more smooth and contiguous pattern resulting in lower resistivity. The resistivity of the silver line obtained by ethylene glycol vapor reduction at 250 °C for 30 min was 12 µΩ cm, which is about eight times higher than that of bulk silver. In contrast, the copper lines were fabricated by reactive inkjet printing and reactive sintering using various conditions of formic acid, ethylene glycol and hydrogen atmosphere, the copper lines printed have no conductivity due to the formation of copper oxide.
Evaluation of Vacuum Ultraviolet Irradiation Influence under Xenon Excimer Lamp Processing Employing a Quartz Crystal Microbalance with Organic Thin Film
Authors: Yoshino Kiyoshi , Matsumoto Hiroyuki , Iwasaki Tatsuyuki , Kinoshita Shinobu , Noda Kazutoshi , Iwamori Satoru
Published: May 2013

The xenon excimer lamp, which emits vacuum ultraviolet radiation, is frequently used as a dry cleaning device for objects such as flat-panel displays (FPDs). UV dry cleaning processes are generally monitored with UV illuminometers, however these do not detect the direct influence of the cleaning process on the substrate. Therefore, a monitoring method that focuses on the treated substrate is required. In this study, we investigated a method to evaluate VUV influence under xenon excimer lamp processing, using a quartz crystal microbalance technique which can detect very small changes in mass. With an organic (fluorocarbon) thin film as the detecting element of the quartz crystal microbalance, we have investigated mass change through irradiation with a xenon excimer lamp, in nitrogen, oxygen, and air atmosphere, respectively. It was confirmed that mass change increased linearly with time, under all conditions, and that monitoring of VUV influence was possible by means of the quartz crystal microbalance method using fluorocarbon thin film.
Fine-Pitch Copper Wiring Formed with Super-Inkjet and Oxygen Pump
Authors: Shirakawa Naoki , Murata Kazuhiro , Kajihara Yasukazu , Nakamura Katsuhiro , Kashiwagi Yukiyasu , Nakamoto Masami , Sato Hironori , Kojima Toshifumi , Komiya Daisuke , Shimizu Kotaro , Masuda Kazuyuki
Published: May 2013

We have successfully printed wires of 5 µm line widths and spaces in copper nanoparticle ink with a super-inkjet printer. The wires show resistivity as low as 8.1 µΩ·cm after sintering at 250 °C in an extremely low oxygen atmosphere generated by an oxygen pump. To our knowledge, this is the first report of micron-scale copper wiring formed by a direct printing method without any masks or templates.
Fundamental Characteristics of Bioprint on Calcium Alginate Gel
Authors: Umezu Shinjiro , Hatta Tatsuru , Ohmori Hitoshi
Published: May 2013

The goal of this study is to fabricate precision three-dimensional (3D) biodevices those are micro fluidics and artificial organs utilizing digital fabrication. Digital fabrication is fabrication method utilizing inkjet technologies. Electrostatic inkjet is one of the inkjet technologies. The electrostatic inkjet method has following two merits; those are high resolution to print and ability to eject highly viscous liquid. These characteristics are suitable to print biomaterials precisely. We are now applying for bioprint. In this paper, the electrostatic inkjet method is applied for fabrication of 3D biodevices that has cave like blood vessel. When aqueous solution of sodium alginate is printed to aqueous solution of calcium chloride, calcium alginate is produced. 3D biodevices are fabricated in case that calcium alginate is piled.
Inkjet-Printed Memristor: Printing Process Development
Authors: Nelo Mikko , Sloma Marcin , Kelloniemi Jaakko , Puustinen Jarkko , Saikkonen Teuvo , Juuti Jari , Häkkinen Juha , Jakubowska Malgorzata , Jantunen Heli
Published: May 2013

In the last five years, research on memristive devices has been under ever increasing interest. Additionally, recent development in printed techniques provides new approaches to fabricate also memristive devices in inexpensive and flexible manner. Thus their research is an important effort towards fully printed electronics applications. In this work, an organometallic precursor solution for a memristive layer was synthesised and formulated for inkjet-printable form. Layers of the solution were determined with surface profilometry in order to find feasible layer thickness for memristive behaviour. Memristors were inkjet-printed on copper- and titanium-coated glass sheets, and various heat-treatments were carried out. The influence of the heat-treatments on the durability and resistance values of the memristors was evaluated. Microstructural and phase changes in the memristive layer were observed with X-ray diffraction and field emission scanning electron microscopy analysis.
Gas Sensors Based on Organic Field-Effect Transistors: Role of Chemically Modified Dielectric Layers
Authors: Mori Tomohiko , Kikuzawa Yoshihiro , Noda Koji
Published: May 2013

Organic field-effect transistors (OFETs) were fabricated on chemically modified SiO2 dielectric layers. Changes in the mobility of the OFETs upon exposure to humidity were measured. The chemically modified dielectric layers change the OFETs' sensitivity to humidity. There is a good correlation between the sensitivity to humidity and the surface free energy of the dielectric layers. Our data suggest that surfaces with low surface free energy have low humidity adsorption probability; therefore, the corresponding OFETs also display low sensitivity to humidity. Our findings indicate that the sensitivity of OFET-based gas sensors can be tuned by using chemically modified dielectric layers.
Study of Hole-Injection Assisted Layer in Double-Layer Organic Light-Emitting Diodes by Electric-Field-Induced Optical Second-Harmonic Generation Measurement
Authors: Sadakata Atsuo , Oda Yoshiaki , Taguchi Dai , Fukuzawa Masahiro , Manaka Takaaki , Iwamoto Mitsumasa
Published: May 2013

By using electric-field-induced optical second-harmonic generation (EFISHG) measurement, we studied the physical reason for the decrease in the threshold voltage of indium tin oxide (ITO)/N,N
′-di-[(1-naphthyl)-N,N
′-diphenyl]-(1,1′-biphenyl)-4,4′-diamine (α-NPD)/tris(8-hydroxy-quinolinato)aluminum(III) (Alq3)/Al diodes with a pentacene layer sandwiched between ITO and α-NPD layers. The amount of charge accumulated at the α-NPD/Alq3 interface was the same as that at ITO/α-NPD/Alq3/Al diodes under an applied DC voltage corresponding to the threshold voltage, although the charge accumulation proceeded faster. Results showed that the pentacene layer assists hole injection and the succeeding hole accumulation at the α-NPD/Alq3 interface, followed by the electroluminescence (EL) emission. The decrease in threshold voltage by inserting a hole-injection assisted layer such as pentacene is one way of improving the EL device performance.
Charge Accumulation in Organic Solar Cells during Device Operation as Investigated by Electron Spin Resonance
Authors: Nagamori Tatsuya , Marumoto Kazuhiro
Published: May 2013

An electron spin resonance (ESR) method was applied to bulk-heterojunction organic thin-film solar cells to investigate the accumulated charges in such devices under simulated solar irradiation. The device structure used was an indium–tin oxide/poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS)/regioregular poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM)/Pd/LiF/Al. We measured light-induced ESR (LESR) signals and device characteristics simultaneously using the same device. We observed two different LESR signals, namely, a narrow signal (g = 2.0023, ΔH
pp ∼0.2 mT) and a broad signal (g = 2.0034, ΔH
pp ∼1.5 mT). The origin of the narrow signal was confirmed to be the charge accumulation in P3HT. The origin of the broad signal was determined to be the charge accumulation in PEDOT and/or PSS by the spectral simulation of the LESR signal. Moreover, the charge accumulation in PEDOT and/or PSS was found to be related to voltage and current.
Organic Light-Emitting Diode with Highly Ordered Polycrystalline Thin Film
Authors: Nakano Kyohei , Kobori Takeo , Takayashiki Yukiko , Iino Hiroaki , Hanna Jun-ichi
Published: May 2013

We investigate organic light-emitting diodes with a polycrystalline thin film of a calamitic liquid-crystalline material. Compared to a non-liquid-crystalline material, the polycrystalline films fabricated via the liquid-crystalline phase showed high electrical current and light emission from an emissive dye dopant, in spite of a film thickness of over 1 µm. Judging from the X-ray diffraction patterns and polarized optical microscope images, well-controlled parallel molecular orientation and suppression of grain boundaries were achieved only in the liquid-crystalline material owing to the molecular orientation controllability of the liquid-crystalline materials. We conclude that the liquid-crystalline materials can be a good candidate for a polycrystalline organic semiconductor for not only thin-film transistors but also light-emitting diodes and solar cells.
Organic Light-Emitting Diode with Solution-Processed Molybdenum Trioxide from Dilute Aqueous Solution
Authors: Takayama Masaru , Naka Shigeki , Okada Hiroyuki
Published: May 2013

We report on the application of vary thin molybdenum trioxide (MoO3) film deposited by spin-coating from dilute aqueous solution to the organic light-emitting diodes (OLEDs). The device characteristics with solution-processed MoO3 were drastically improved in comparison with the device without MoO3 buffer layer. Luminance and electroluminescent (EL) efficiency were identical to the devices with poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) or vacuum-deposited MoO3 buffer layer. Also, the barrier height at interface of indium–tin-oxide/organic layer is lowered with insertion of spin-coated MoO3. Solution-processed MoO3 from dilute aqueous solution is promising for the buffer layer in the OLEDs.
Advantage of Immobilization of Phthalate Derivatives on Indium Tin Oxide Electrode over TiO2 Electrode in Their Electrochromic Properties
Authors: Ura Naoki , Nakamura Kazuki , Kobayashi Norihisa
Published: May 2013

Electrochromism is known as an electrochemical reaction exhibiting coloration and can be applied to imaging devices. We successfully prepared a novel indium tin oxide (ITO) electrode modified by electrochromic molecules that displayed a magenta color via electrochemical reduction. The electrochromic molecules of a phthalate derivative were connected to the surface of the ITO electrode by a Si coupling agent. The electrochromic properties of the film were investigated in terms of film thickness and were compared to those of a film using a TiO2 substrate. The thicker film showed larger absorption change and better memory retention than did the film with a TiO2 substrate.
Approaches to Realizing Sheet-Type Scanner with Scanning Light Source
Authors: Murase Makoto , Itagaki Motoshi , Miyabayashi Takeshi , Hayashi Hideki , Naka Shigeki , Okada Hiroyuki
Published: May 2013

Organic devices have attracted much attention because it could realize the fabrication of lightweight and flexible devices. Among these devices is the sheet-type scanner. In order to fabricate organic devices on a film substrate, self-alignment (SA) techniques would be useful. First, SA techniques for an organic or oxide thin-film transistor (TFT) were introduced. After that, our study on the structure and property of a scanner device with a scanning light source were reported. Our device had organic photodiodes (OPDs) and organic light-emitting diodes (OLEDs) on the same substrate. The OLEDs were used as the scanning light source and SA-TFTs were used for the active device. The device output signal depended on the distance between reflecting electrodes of OPDs and OLEDs, and the color density of the scanned target was confirmed by the signal.
Dye-Sensitized Solar Cell Utilizing Electrostatic Inkjet
Authors: Umezu Shinjiro , Kunugi Yoshihito , Ohmori Hitoshi
Published: May 2013

Solar cell is one of the key technologies in this century because this has possibility to clear energy problems. We tried to pattern good titania layer of dye-sensitized solar cell (DSC) utilizing electrostatic inkjet. The electrostatic inkjet has good merit; that is ability to eject highly viscous liquid. We applied the merit for patterning titania paste on fluorine-doped tin oxide (FTO) glass. In this paper, we investigated fundamental characteristics to pattern titania layer on FTO glass because efficiency depends on thickness of titania layer.
Roll-to-Roll Screen Printed Radio Frequency Identification Transponder Antennas for Vehicle Tracking Systems
Authors: Zichner Ralf , Baumann Reinhard R.
Published: May 2013

Vehicle tracking systems based on ultra high frequency (UHF) radio frequency identification (RFID) technology are already introduced to control the access to car parks and corporate premises. For this field of application so-called Windshield RFID transponder labels are used, which are applied to the inside of the windshield. State of the art for manufacturing these transponder antennas is the traditional lithography/etching approach. Furthermore the performance of these transponders is limited to a reading distance of approximately 5 m which results in car speed limit of 5 km/h for identification. However, to achieve improved performance compared to existing all-purpose transponders and a dramatic cost reduction, an optimized antenna design is needed which takes into account the special dielectric and in particular metallic car environment of the tag and an roll-to-roll (R2R) printing manufacturing process. In this paper we focus on the development of a customized UHF RFID transponder antenna design, which is adopted for vehicle geometry as well as R2R screen printing manufacturing processes.
Dissociations of C5F8and C5HF7in Etching Plasma
Authors: Hayashi Toshio , Ishikawa Kenji , Sekine Makoto , Hori Masaru
Published: May 2013

Investigations of dissociations for c-C5F8and c-C5HF7molecules in the excited states were carried out using the molecular orbital method. The excitation energy to the lowest triplet state of c-C5F8was lower the sum of the total energy of (C4F6+CF2) triplet state. Fragmentation by electron attachment to c-C5F8did not take place, because the total energy of c-C5F8-is more stable than that of (C4F6+CF2)-. Hence, the main dissociative product of CF2by electron excitation to π–π*state is created in the plasma of c-C5F8and c-C5HF7, with reaction paths of C4F6+CF2and C4HF5+CF2compared with other dissociation paths of C3F4+C2F4and C3HF3+C2F4. These dissociation pathways have suggested advantageous for dielectric etching with fluorine-deficient chemistry.
Selective Etching of Magnetic Tunnel Junction Materials Using CO/NH3 Gas Mixture in Radio Frequency Pulse-Biased Inductively Coupled Plasmas
Authors: Jeon Min Hwan , Kim Hoe Jun , Yang Kyung Che , Kang Se Koo , Kim Kyong Nam , Yeom Geun Young
Published: May 2013

The etch characteristics of magnetic tunneling junction (MTJ) materials and the etch selectivity over W have been investigated using RF pulse-biased conditions in addition to the continuous wave (CW) bias condition with a CO/NH3 gas combination in an inductively coupled plasma system. By using a time-averaged substrate DC bias voltage condition for the RF pulse biasing, the etch rates of MTJ materials for the RF pulse-biased conditions were generally similar to those etched using the CW RF bias condition even though the etch rates were slightly decreased with decreasing the duty percentage of the RF pulse biasing. However, the use of the RF pulse biasing improved the etch selectivity of the MTJ materials over mask materials such as W. When the surface roughness and the residual thickness remaining on the etched surface of the MTJ material such as CoFeB were investigated by using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS), respectively, it was clear that the use of the RF pulse biasing instead of CW RF biasing also decreased the residual thickness and the surface roughness. This is believed to be related to the formation of a more uniform chemically reacted layer on the etch CoFeB surface during the RF pulse-biased etching condition.
Negative Impact of Etched Si Area on Selectivity and Positive Impact of Photoelectric Current on Etched Profile in Gate Etching with Different Wafer Bias Frequencies
Authors: Kamibayashi Masami , Kofuji Naoyuki , Mori Masahito , Negishi Nobuyuki
Published: May 2013

The effect of wafer-bias frequency on the dummy-gate fabrication of fin-shaped field-effect transistor (Fin-FET) was investigated. The clear difference in the selectivity of polycrystalline silicon to SiO2between 400 kHz and 13.56 MHz decreased when the etched Si area increased. On the other hand, a higher frequency increased such selectivity when Si area decreased. These results can be explained by the effect of by-product deposition. As for the etched profile, the amount of side etching was much larger at 13.56 MHz than at 400 kHz. It was reported that this phenomenon is caused by local charging. It was also suggested that the charging should be suppressed by reducing the ratio of ion saturation current to photoelectric current. Therefore, in this study, we investigated the effect of such current ratio on side etching. The result confirmed that a reduction in current ratio induced by increasing gas pressure decreases the amount of side etching.