bluuebunny/crossref_metadata_2025 huggingface dataset:
Coaxial Holographic Memory with Designed Reference Pattern on the Basis of Nyquist Aperture for High Density Recording
Authors: Nobukawa Teruyoshi , Nomura Takanori
Published: October 2013

We propose the designed reference pattern on the basis of the Nyquist aperture for a coaxial holographic memory and investigate its recording performance by numerical simulations. By using the designed reference pattern, the Fourier power spectrum of a reference beam spreads uniformly within the Nyquist aperture, thereby an interference efficiency, a signal-to-noise ratio (SNR) and a symbol error rate (SER) are improved relative to conventional method with a random binary phase mask. Moreover, in the case of applying the 1.25 times aperture than the Nyquist size, the proposed method can record data pages with higher SNR and lower SER than that of conventional method with 2 times aperture than the Nyquist size. Numerical results imply that our proposed method can record data pages at a smaller area of recording media than that of conventional method.
Growth of Thin Epitaxial CaxSr1-xF2/SrF2 Layers with Low Leakage Current on Ge Substrates
Authors: Takahashi Keita , Tsutsui Kazuo
Published: October 2013

Resonant tunneling structures composed of epitaxial fluoride layers with a large conduction band discontinuity grown on Si or Ge substrates are attractive for the monolithic integration of quantum devices with CMOS. We found that the leakage current of Ca0.42Sr0.58F2 (lattice-matched with Ge) layers on Ge substrates was unusually large, which has not been observed on Si substrates. From an investigation of the dependence of the alloy composition of the fluoride layers on the leakage, the introduction of a SrF2 buffer layer, i.e., a Ca0.42Sr0.58F2/SrF2/Ge structure, was proposed as a technique for the growth of an electron-tunneling barrier layer on Ge with low leakage current.
A Novel Way to Fabricate Superhydrophilic and Antibacterial TiO2 Nanofilms on Glass by Ion Implantation and Subsequent Annealing
Authors: Cai Guangxu , Ren Feng , Liu Yichao , Wu Wei , Fu Dejun , Xiao Xiangheng , Jiang Changzhong
Published: October 2013

We report a simple and novel method to fabricate high quality titanium dioxide (TiO2) nanofilms on soda lime glass by a solid phase growth process of Ti implantation and subsequent annealling at 500 °C in oxygen atmosphere. The formation of the TiO2 nanofilms is resulted from the slow out-diffusion of implanted Ti ions from the substrates and being oxidized at the surfaces. The formed TiO2 nanofilms show superhydrophilicity and good antibacterial property with good adhesion to substrate and stability, suggesting that the TiO2 nanofilms formed by this method have great potential applications such as antibacterial, anti-fog and self-cleaning transparent glass.
Improvement of Organic Solar Cells by Anode Buffer Composed of Evaporated Gold Nanoparticles
Authors: Wang Dan , Yukitake Noriaki , Fujita Katsuhiko
Published: October 2013

We here report that evaporated gold islands with mean sizes of 2–3 nm can enhance the hole injection at the anode/organic semiconductor in organic devices. The enhancement was observed only after UV–ozone treatment. It was indicated by elemental analysis that the evaporated gold was partially oxidized by the treatment. The oxidized layer would act as an insulator to increase the work function of the electrode. By inserting a hyper-branched polymer, the work function further increased. This method can also be employed in an anode buffer for organic solar cells to improve the device performance.
CO Gas Detection of Al-Doped ZnO Nanostructures with Various Shapes
Authors: Wang Byung-Yong , Lim Dae-Soon , Oh Young-Jei
Published: October 2013

Nanostructure of semiconductor type gas sensors that are high sensitivity, fast response time, inexpensive, and easily fabricated, is suggested. One-dimensional (1D) nanostructures, such as nanorods, and hollow spheres, are attracting particularly great interest because of their large specific surface area and their inherent physical properties. This study combined with ZnCl2(6.95 g, Sigma-Aldrich), Al(NO3)3·9H2O (Junsei), NaOH, ethanol, and deionized water (DI) by hydrothermal synthesis to manufacture, spherical, hollow, hierarchical, and nanorod. The same Al-doped ZnO (AZO) were prepared by a colloidal template on a Si wafer to make a 3D igloo structure as well. Sensitivity to carbon monoxide at 50 ppm was tested at 250 °C the compare the sensing properties. Gas sensitivity of the hierarchical structure showed the highest sensitivity at 31.8, a figure 7 times that of the packed spherical sphere, whereas the igloo structure gave the fastest response speed of 32 s. The results of various shapes of the AZO nanostructures demonstrated high sensitivity and quick response time, which is useful in the detection of harmful gases in automobiles and the atmosphere.
Adsorption of Primary Alcohol Molecules on Trigonal Selenium Nanowires
Authors: Akiyama Norio , Ohtani Tsukio
Published: October 2013

The gas sensor responses of bundled trigonal-selenium nanowires (t-SeNWs) were investigated for the series of primary alcohols (CnH2n+1OH;n= 1–10) at room temperature. It was found that the primary alcohol molecules forn= 1–4 were adsorbed simply on the SeNW surface asnincreased. Primary alcohol molecules withn= 5–10 had different characteristic behaviors than those withn= 1–4. The adsorption configuration of primary alcohol molecules on the surfaces of t-SeNWs is discussed.
Vibrational Behavior of Single-Walled Carbon Nanotubes: Atomistic Simulations
Authors: Chang I-Ling , Huang Chang-Ming
Published: October 2013

This study examines the vibrational behaviors of both armchair and zigzag carbon nanotubes (CNTs). The natural longitudinal/flexural/torsional/radial frequencies of CNTs were extracted and analyzed simultaneously from an equilibrium molecular dynamics (MD) simulation without imposing any initial modal displacement or force. Initial random atomic velocities, which were assigned to fit the simulated temperature, could be considered as an excitation on CNTs composing of wide range of spatial frequencies. The position and velocity of each atom at every time step was calculated using finite difference algorithm, and fast Fourier transform (FFT) was used to perform time-to-frequency domain transform. The effects of CNT length, radius, chirality, and boundary condition on the vibrational behaviors of CNTs were systematically examined. Moreover, the simulated natural frequencies and mode shapes were compared with the predictions based on continuum theories, i.e., rod, Euler–Bernoulli beam and nonlocal Timoshenko beam, to examine their applicability in nanostructures.
Nanoimprint Lithography of 20-nm-Pitch Dot Array Pattern Using Tone Reversal Process
Authors: Ootera Yasuaki , Sugawara Katsuya , Kanamaru Masahiro , Yamamoto Ryousuke , Kawamonzen Yoshiaki , Kihara Naoko , Kamata Yoshiyuki , Kikitsu Akira
Published: October 2013

The nanoimprint lithography (NIL) of a hexagonal dot array pattern with 20 nm pitch was demonstrated using a tone reversal process. The dot array was formed by the self-assembled polystyrene–poly(dimethylsiloxane) (PS–PDMS) diblock copolymer. The dot pattern was transferred to a hole pattern on the imprint resist layer by a UV-NIL process. The hole pattern was filled with spin-on-glass (SOG). By removing the imprint resist matrix, the SOG dot pattern was formed as a final mask layer. The surface tension of the imprint resist was adjusted to achieve high-quality pattern transfer and demolding. The standard deviation of the diameter and pitch of the dot pattern suffered about 1% drop through the UV-NIL and tone reversal process.
Effect of Small Microfabrication Damage on Optical Characteristics of Laser Structure with GaInNAs Quantum Well
Authors: Goto Hiroaki , Ishikawa Fumitaro , Morifuji Masato , Kondow Masahiko
Published: October 2013

We investigate the effect of micro-fabrication process damage on the photoluminescence characteristics of laser structures containing a GaInNAs and GaInAs quantum wells. By varying the size of the fabricated island structure, its impact on the photoluminescence intensity is studied. The GaInAs sample shows a strong decrease in its intensity with the reduction of the island size. In contrast, a slight increase is observed from the GaInNAs sample. This indicates the negligible impact of surface recombination on the GaInNAs sample, as well as the optical confinement within the micrometer-size island structure. The results suggest the feasibility of a GaInNAs gain medium for application to microfabricated optical devices.
Detection of Radiation Tracks Recorded on Silver-Salt Photographic Materials by Fluorescence-Labeling Method
Authors: Kuge Ken'ichi , Inoue Ryouhei , Oishi Yasushi , Yasuda Nakahiro , Kodaira Satoshi , Sato Osamu
Published: October 2013

We have proposed a new fluorescence-labeling method to detect radiation tracks recorded on silver-salt photographic materials. Fluorescence images of tracks were obtained by converting the developed silver to silver iodide as a mordant by bleaching and selectively adsorbing a fluorescent dye, namely, 3,3'-diethyl-2,2'-oxacyanine iodide, on it. The dye emitted blue and green fluorescent lights in the adsorbed state to silver iodide. Even tracks masked with fake particles could be recognized clearly in the fluorescence images, because the dye was adsorbed only on silver iodide. This new fluorescence-labeling method will facilitate the development of new technologies for the analysis of radiation tracks on the basis of the color information obtained from the tracks.
Development of a Low-Temperature Insert for Precise Magnetization Measurement below T = 2 K with a Superconducting Quantum Interference Device Magnetometer
Authors: Sato Yoshiaki , Makiyama Shun , Sakamoto Yasutaka , Hasuo Tadahiko , Inagaki Yuji , Fujiwara Tetsuya , Suzuki Hiroyuki S. , Matsubayashi Kazuyuki , Uwatoko Yoshiya , Kawae Tatsuya
Published: October 2013

We have developed a 9-mm-diameter 3He insert for precise magnetization measurements below T = 2 K that is attachable to a commercial superconducting quantum interference device magnetometer. The insert is made from a thin-walled stainless steel pipe with an inner diameter of 6.2 mm, which determines the maximum sample size. 3He gas is condensed in the pipe, which is liquefied by 4He gas at T ∼1.8 K generated by the magnetometer via the heat exchanger of a Cu vacuum jacket with an outer diameter of 8.6 mm soldered to the stainless steel pipe. The temperature of the insert is decreased to T ∼0.5 K by evacuating liquid 3He using a rotary pump and then to T = 0.36 K with a sorption pump. From the diamagnetization signal of a superconducting Al chip with a mass below 0.1 mg, the magnetization resolution with the insert is confirmed to be less than 10-7 emu. To examine the performance of the insert, we measured the temperature dependence of the magnetic susceptibility and magnetization for Pr0.6La0.4Ag2In down to T = 0.4 K.
Fabrication of Thin-Film Transistor Integrated Circuits on Flexible Substrate by Transfer Technique of Carbon Nanotube Network Using Poly(vinyl alcohol)
Authors: Ishii Satoshi , Nishu Mamoru , Kishimoto Shigeru , Mizutani Takashi
Published: October 2013

Flexible integrated circuits consisting of carbon nanotube thin-film transistors (CNTTFTs) were fabricated on a poly(ethylene naphthalate) (PEN) substrate by the transfer technique of the CNT network. The CNT network grown on a SiO2/p+-Si substrate by plasma-enhanced chemical vapor deposition was transferred onto the PEN substrate using poly(vinyl alcohol) (PVA). A delay time of 1.1 µs/gate was realized for the ring oscillator with a channel length of 10 µm. The present delay time is the best ever reported to our knowledge among CNTTFT flexible integrated circuits using transferred or printed CNT networks.
Observation of Motion of Bowed Strings and Resonant Strings in Violin Performances
Authors: Matsutani Akihiro
Published: October 2013

The motion of a bowed string and a resonant string of a violin were simultaneously observed for the first time. The results of the direct observation of string motion in double stops and harmonics are also presented. The importance of the resonance was experimentally demonstrated from these observations. It is suggested that players should take account of the resonance and ideal Helmholtz motion in violin performances.
Detection and Two-Dimensional Imaging of Escherichia coli Attached to an Optical Disk
Authors: Shima Takayuki , Gopinath Subash C. B. , Fujimaki Makoto , Awazu Koichi
Published: October 2013

Escherichia coli detection was conducted using an optical disk drive tester. A sample of E. coli was mixed in deionized water to obtain an optical density of 0.1 at a wavelength of 600 nm. The solution was dropped onto an oxide-coated disk, on which positioning marks had been made, and dried. Two-dimensional imaging of the E. coli dispersed on the surface was carried out using the marks, and the image obtained was similar to that obtained by an optical microscope. The results indicate that this system can be used to identify the size and number of E. coli.
Leakage Current Suppression on Metal-Induced Laterally Crystallized Polycrystalline Silicon Thin-Film Transistors by Asymmetrically Deposited Nickel
Authors: Byun Chang Woo , Son Se Wan , Lee Yong Woo , Park Jae Hyo , Takaloo Ashkan Vakilipour , Joo Seung Ki
Published: October 2013

The electrical performance of low-temperature polycrystalline silicon (LTPS) thin-film transistors (TFTs) fabricated by metal-induced lateral crystallization (MILC) is greatly affected by metal catalyst contaminations, such as Ni and Ni silicide trapped in the channel, since they concentrate in front of laterally grown crystallites. In the present work, the effect of the MILC/MILC boundary (MMB) on MILC polycrystalline silicon (poly-Si) TFTs is investigated by the comparison of MILC poly-Si TFTs with MMB at the center of the channel, and equivalent TFTs with MMB at a position ejected from the channel. The MMB location was controlled by the Ni catalyst position. Both a low off-state leakage current and a free from short channel effect (kink effect) were observed in high electric-field conditions. Furthermore, the field-effect mobility and drain current noise were drastically improved by ejecting the MILC boundary in the source direction.
Electrical Characteristics of Ti/Al Contacts on AlInN:Mg/GaN Heterostructures
Authors: Kim Seongjun , Kim Hee Jin , Choi Suk , Lochner Zachary , Ryou Jae-Hyun , Dupuis Russell D. , Ahn Kwang-Soon , Kim Hyunsoo
Published: October 2013

The electrical characteristics of a Ti/Al metal contact on Mg-doped AlInN/GaN heterostructures were investigated using a transmission line model. The as-deposited Ti/Al contact exhibited near Ohmic contact with a specific contact resistance of 1.78×10-2Ω cm2, while the thermal annealing performed at 600 °C led to better Ohmic contact with a contact resistance of 9.38×10-4Ω cm2. This could be attributed to the formation of a direct Ohmic path connecting the contact and the two-dimensional electron gas beneath an AlInN:Mg barrier upon thermal annealing, namely, a spike contact through the indiffusion of Al as verified from secondary ion mass spectroscopy. Current–voltage–temperature measurements showed an insignificant temperature dependence in both the sheet resistance and the contact resistance, which seemed to be associated with the distinctive feature of the spike contact.
Numerical Study on Recombination Efficiency at 4,4'-Bis(2,2'-diphenylvinyl)-1,1'-spirobiphenyl/Tris(8-quinolinolato)aluminium Interface in Organic Light Emitting Diodes
Authors: Hwang Young Wook , Kim Kwang Sik , Won Tae Young
Published: October 2013

In this paper, we report our numerical study on the electrical and optical properties of the organic light emitting diodes (OLEDs) devices with n-doped layer, which is inserted for the purpose of reducing the interface barrier height between the cathode and the electron transport layer (ETL). We performed finite element method (FEM) simulation on OLEDs in order to understand the transport behavior of carriers, recombination kinetics, and emission property. Our model includes Poisson's equation, continuity equation to account for behavior of electrons and holes and exciton continuity/transfer equation to account for recombination of carriers. We employ the multilayer structure which consists of indium tin oxide (ITO); 2,2',7,7'-tetrakis(N,N-diphenylamine)-9,9'-spirobi-fluorene (S-TAD); 4,4'-bis(2,2'-diphenylvinyl)-1,1'-spirobiphenyl (S-DPVBi); tris(8-quinolinolato)aluminium (Alq3); calcium (Ca).
Effect of Ar Ion Beam Pre-Treatment of Poly(ethylene terephthalate) Substrate on the Mechanical and Electrical Stability of Flexible InSnO Films Grown by Roll-to-Roll Sputtering System
Authors: Choi Kwang-Hyuk , Kim Han-Ki
Published: October 2013

We investigated the effects of Ar ion beam irradiation on a flexible poly(ethylene terephthalate) (PET) substrate as surface pre-treatment method in the roll-to-roll (R2R) sputtering system and its contribution to the electrical durability of flexible InSnO (ITO) electrode upon that the flexible PET substrate under repeated mechanical stresses. It was found that the Ar ion beam irradiation of the flexible PET surface could improve an adhesion between R2R sputter-grown ITO film and the PET substrate. X-ray photoelectron spectroscopy results showed that the Ar ion beam irradiation lead to an increase of hydrophilic functional groups when the working pressure, Ar ion beam power, and exposure time increases. Repetitive bending stresses for the flexible ITO/PET film which fabricated through the surface pre-treatment by Ar ion beam irradiation showed more stable electrical durability than those of ITO films on the wet-cleaned PET substrate due to enhanced interfacial adhesion between the ITO film and PET surface. This suggests that the Ar ion beam pre-treatment before sputtering of ITO film in R2R sputtering system is an effective technique to improve the adhesion between ITO film and PET substrate.
Microstructures of Polycrystalline Silicon Wafer Directly Grown on Si3N4 Substrate from Liquid Silicon
Authors: Jang Bo Yun , Lee Jin Seok , Ahn Young Soo
Published: October 2013

Polycrystalline silicon (Si) wafers were directly grown on Si3N4 substrate using a horizontal growth process and the their microstructures were observed. Si wafer with a dimension of 50×80 mm2 was successively achieved and typical growth velocity was 315–926 cm/min. From the investigations of process, microstructures were mainly determined by the substrate movement velocity, which was equal to the growth velocity. When the movement velocity increased, the wafer thickness and grain sizes decreased, but, the number of twins increased. When the movement velocity was 315.6 cm/min, wafer thickness was 312 µm and mean grain size was 82 µm. When the graphite substrate was used, there was severe carbon contamination and SiC was even formed near the rear side of wafer. Substitution of the substrate material with Si3N4 instead of graphite reduced the amount of carbon from about 1×1020 to 5.87×1018 atoms/min.
Effect of Heating Rate on the Refining of Metallurgical-Grade Silicon during Fractional Melting
Authors: Chung Juho , Lee Changbum , Yoon Wooyoung
Published: October 2013

Silicon was purified using fractional melting (FM), which is a more effective refining method than fractional solidification. Changes in the silicon microstructure during FM were observed using a scanning electron microscope (SEM) and an electron probe microanalyzer (EPMA). Purity of each sample was investigated using inductively coupled plasma atomic emission spectrometry (ICP-AES) to determine the effects of various heating rates on the efficiency of FM. A refining ratio of 97.28% was the best result that could be obtained for the sample that was heated at a rate of 15 °C/min. For the samples that were heated below 1390 °C lower heating rate resulted in higher refining efficiency. Acid-leaching yielded 99.98% pure silicon samples after FM.
Thermoelectric Properties of Non-Stoichiometric β-Zn3.83 + δSb3 Polycrystals Sintered by a Hot-Press Method
Authors: Choi Soon-Mok , Song Minseok , Moon Jooho , Seo Won-Seon , Jang Kyung-Wook
Published: October 2013

In a moderate temperature range (450–650 K), β-Zn3.83 + δSb3 has numerous advantages because the figure-of-merit (Z
T) of β-Zn3.83 + δSb3 is the highest in this temperature range. However there are difficulties when attempting to control the stoichiometry so as to manufacture Zn3.83 + δSb3 specimens. In this study, three different compositions, Zn3.83Sb3 [δ (excess Zn) = 0], Zn3.9Sb3 (δ= 0.07), and Zn4Sb3 (δ= 0.17), were designed to obtain a β-Zn3.83 + δSb3 single phase through a hot-press sintering process. An investigation for the temperature dependence of thermoelectric properties confirmed that the Zn4Sb3 (δ= 0.17) composition hot-pressed at 723 K was the optimized condition for obtaining the Zn3.83 + δSb3 single phase representing best thermoelectric properties. As a result, a maximum Z
T value of 1.33 was obtained at a measuring temperature of 664 K for the Zn4Sb3 (δ= 0.17) composition hot-pressed at 723 K.
Study on the Fabrication of Paint-Type Si Quantum Dot-Sensitized Solar Cells
Authors: Seo Hyunwoong , Son Min-Kyu , Kim Hee-Je , Wang Yuting , Uchida Giichiro , Kamataki Kunihiro , Itagaki Naho , Koga Kazunori , Shiratani Masaharu
Published: October 2013

Quantum dots (QDs) have attracted much attention with their quantum characteristics in the research field of photochemical solar cells. Si QD was introduced as one of alternatives to conventional QD materials. However, their large particles could not penetrate inside TiO2layer. Therefore, this work proposed the paint-type Si QD-sensitized solar cell. Its heat durability was suitable for the fabrication of paint-type solar cell. Si QDs were fabricated by multihollow discharge plasma chemical vapor deposition and characterized. The paste type, sintering temperature, and Si ratio were controlled and analyzed for better performance. Finally, its performance was enhanced by ZnS surface modification and the whole process was much simplified without sensitizing process.
Improvement in Cycle Performance by Suppression of Surface Reaction between Electrolyte and LiV3O8 Electrode Using Gel Polymer Electrolyte
Authors: Seo Jung Min , Yom Jee Ho , Yoon Woo Young , Kim Dong Won
Published: October 2013

Amorphous lithium trivanadate (LVO) exhibits a higher capacity than crystalline LVO. However, products are generated from the reaction between the surface of an amorphous LVO electrode and the surrounding electrolyte during charging and discharging. The continuous reaction between the electrode surface and surrounding electrolyte was inhibited using a gel-polymer electrolyte (GPE) instead of a conventional liquid electrolyte. After 100 cycles, the GPE-based cell shows 54% of capacity retention, which was 9% higher capacity retention than that of the conventional liquid electrolyte cell. The GPE is prepared as Kynar 2801 polymer and the charge and discharge performances of the cell were measured using a standard battery cycling test at a 0.5 C-rate and 1.5–4.0 V cut off voltage. The morphologies of the electrode surfaces and the various products formed on the electrode surfaces during the reaction were analyzed using scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy, respectively.
Irreversible Behaviors and Kinetics of Lithiated Products in SiOx Anodes with Inserting Li contents in Li Ion Batteries
Authors: Lee Jun Kyu , Kim Bok Ki , Yoon Woo Young
Published: October 2013

The irreversible behavior of SiO
x
anodes during cycling has been investigated by controlling the amount of Li inserted during lithiation. This study mainly focuses on evaluating the amount of irreversible capacity by varying the amount of Li inserted into the SiO
x
(0.1, 0.5, 1, 2, and 4 mol Li per mol of SiO
x
, the so called “mol rate”) and investigating the lithiated products using X-ray photoelectron spectroscopy (XPS) after various numbers of cycles were performed at a 0.1 mol rate. It is notified that the irreversible capacity of the SiO
x
anode increases with increasing lithiation mol rates, meaning that the reaction products (Li2O, Li15Si4, and Li–Si–O products) have different reaction kinetics during lithiation. In particular, the XPS investigations showed that the first reaction product is Li2O, the second reaction product is Li–Si alloy (Li15Si4), and the final reaction product is the Li–Si–O products.
Fabrication of Lead-Free Lithium-Doped Na0.5K0.5NbO3 Piezoelectric Ceramics with Dense Grain Structure Using Sol–Gel Surface Coating
Authors: Lim Sun Kyung , Han Jeong Seon , Yoo Ae Ri , Lee Seong Eui , Lee Hee Chul
Published: October 2013

Lead-free piezoelectric 0.06(LiNbO3)–0.94(Na0.5K0.5)NbO3 (LNKN) ceramics in disc form were fabricated and characterized to acquire good electromechanical properties. A molding method including cold isostatic pressing (CIP) was used to form a dense and regular microstructure and suppress the cracking problems of LNKN ceramics during the following high-temperature sintering. The LNKN ceramic sintered at 1040 °C showed a high piezoelectric constant d
33 of 170 pC/N owing to its high density. Furthermore, perovskite LNKN films with the same composition as the ceramics were fabricated using 2-methoxyethanol-based sol–gel solution. The sol–gel surface coating on the LNKN ceramics was found to be very effective for increasing the piezoelectric constant because of the interface stabilization effect leading to a uniform electric field in piezoelectric elements. As a result, we obtained the highest piezoelectric constant d
33 of 183 pC/N. The lead-free LNKN ceramics are promising for applications in eco-friendly ferroelectric and piezoelectric devices.
Electrochemical Study of Hydrocarbon-Derived Electrolytes for Supercapacitors
Authors: Noorden Zulkarnain A. , Matsumoto Satoshi
Published: October 2013

In this paper, we evaluate the essential electrochemical properties – capacitive and resistive behaviors – of hydrocarbon-derived electrolytes for supercapacitor application using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The electrolytes were systematically prepared from three hydrocarbon-derived compounds, which have different molecular structures and functional groups, by treatment with high-concentration sulfuric acid (H2SO4) at room temperature. Two-electrode cells were assembled by sandwiching an electrolyte-containing glass wool separator with two active electrodes of activated carbon sheets. The dc electrical properties of the tested cells in terms of their capacitive behavior were investigated by CV, and in order to observe the frequency characteristics of the constructed cells, EIS was carried out. Compared with the tested cell with only high-concentration H2SO4 as the electrolyte, the cell with the derived electrolytes exhibit a capacitance as high as 135 F/g with an improved overall internal resistance of 2.5 Ω. Through the use of a simple preparation method and low-cost precursors, hydrocarbon-derived electrolytes could potentially find large-scale and higher-rating supercapacitor applications.
Thermoelectric Properties of LazFe4-xCoxSb12 Skutterudites
Authors: Park Kwan-Ho , Kim Il-Ho , Choi Soon-Mok , Lim Young Soo , Seo Won-Seon , Kim Kyung-Hoe
Published: October 2013

La-filled skutterudites (La
z
Fe4-x
Co
x
Sb12) were prepared by encapsulated melting and hot pressing, and filling and doping (charge compensation) effects on the transport and thermoelectric properties were examined. The signs of the Hall and Seebeck coefficients were positive and it means that the majority carriers are holes (p-type). The electrical and thermal conductivities were reduced by substitution of Co for Fe, which was responsible for the decrease in carrier concentration. La0.9Fe3CoSb12 shows the maximum dimensionless thermoelectric figure of merit: Z
T
max = 0.65 at 823 K.
Quantitative Analysis of Transmission Zeros in Cross-Coupled Two-Port Power Systems
Authors: Um Keehong
Published: October 2013

In this paper, we present a practical and quantitative method for theoretical determination of the complex transmission zero locations of lumped two-port power systems. We have derived several closed-forms of transmission zero characteristic equations in order to prove an important result – that the integer pairs of complex transmission zeros originate solely from the cross-coupled portion of the system.
Electrical Properties of BaTiO3-Based Multilayer Ceramic Capacitors Sintered with Plasma-Treated Glass Powder
Authors: Jeong Dae-Yong , Lee Soon-il , Lee Heun-Young , Kim Min-Kee , Yoon Jung-Rag
Published: October 2013

The influence of glass power morphology on the electrical and microstructural properties of BaTiO3-based multilayer ceramic capacitors (MLCCs) was investigated to enhance the reliability of MLCCs. For a sintering additive, glass particles of different sizes and shapes were prepared by jet-milling and RF plasma treatment. Plasma treatment decreased the glass particle size and transformed the irregular shape of glass particles into homogeneous spherical shapes. It was found that MLCCs sintered with plasma-treated glass powder have a more homogeneous microstructure, a clear core–shell structure, a more stable capacitance against voltage and temperature changes, and a higher degradation resistance. It is inferred that nanosized spherical glass powder prepared by plasma treatment helps so-called magic dopants such as rare-earth elements to be distributed homogeneously around the BaTiO3 particles.
Development of Direct Deep Reactive Ion Etching Process Using Laser Interference Lithographed Etch Barrier without Intermediate Layer
Authors: Je Soonkyu , Shim Jongmyeong , Kim Joongeok , Kim Minsoo , Lee Jinhyung , Nho Heejin , Han Jungjin , Kim Seok-min , Kang Shinill
Published: October 2013

Laser interference lithography (LIL) is a technique that allows maskless patterning of large areal periodic nano/micro structures. The LIL pattern is often used as an etch barrier to pattern SiO2intermediate layer in the fabrication process of high aspect ratio silicon nano/micro structures by deep reactive ion etching process (DRIE) with SiO2etch barrier. In this study, a method to fabricate high aspect ratio nanograting structures by direct DRIE process of silicon substrate using LIL pattern without intermediate layer was developed as a simple and cost-effective fabrication process. To fabricate high aspect ratio silicon nanograting with high pattern fidelity, a simulation method to predict the cross sectional profile of photoresist (PR) pattern after exposure and development processes was investigated, and the LIL processing conditions were selected to obtain optimized cross sectional profile of PR pattern without residual layer based on the simulation results. To minimize the side wall defects during the DRIE process due to the deterioration of LIL pattern etch barrier, the processing conditions of DRIE process including etching gas, etching gas ratio, passivation time and power were optimized. Finally, a silicon nanograting with a grating pitch of 780 nm and height of 2.42 µm (aspect ratio: 6) was fabricated via the developed direct DRIE process with LIL pattern.
High Current Density Effect on In-situ Atomic Migration Characteristics of a BiTe Thin Film System
Authors: Kim Seunghyun , Park Yong-Jin , Joo Young-Chang , Park Young-Bae
Published: October 2013

Understanding fundamental atomic migration characteristics of multicomponent chalcogenide materials such as GeSbTe (GST) and BiTe are important in order to investigate the failure mechanism related to the electrical reliability of thermoelectric materials under high current density. In this work, high current density effect on the in-situ atomic migration characteristics of the BiTe thermoelectric thin films was conducted by real-time observation inside an scanning electron microscope chamber. Under the high current density conditions ranging from 0.83×106 to 1.0×106 A/cm2 at 100 °C, Te migrated toward the cathode, and Bi migrated toward the anode because the electrostatic force was dominant by very high Joule heating effect.
Tb0.3Dy0.7Fe1.9/PbZr0.52Ti0.48O3 Micro-Bridge on SiNx Thin Film for Low Frequency Magnetic Sensing Applications
Authors: Lee Dong Gun , Han Jun Hyun , Lee Junwoo , Choi Wook , Yoo Yong Kyung , Kim Jinseok , Hwang Kyo Seon , Kim Tae Song , Chun Dong Won , Kim Yu-Chan , Lee Kyu Hyoung , Lee Jeong Hoon
Published: October 2013

A micro-fabricated bridge sensor for determining minute magnetic field variation is proposed. A micro-bridge with 100×400 µm2 dimensions (width × length) comprises a multi-layered structure of Tb0.3Dy0.7Fe1.9/SiO2/Pt/PbZr0.52Ti0.48O3/Pt/Ta on a SiN
x
supporting layer. We observed the limit of detection under small DC magnetic field as 1×10-11 T which was converted electrically to 77 µV with a 5 µV noise floor via elastic coupling between magnetostrictive and piezoelectric thin film. The magnetoelectric (ME) voltage was linearly proportional to small magnetic field variance, and the experimental ME coefficient was measured as 9.9 V/(cm·Oe).
The Effect of Microstructure on the Thermoelectric Properties of Polycrystalline Higher Manganese Silicides
Authors: An Tae-Ho , Choi Soon-Mok , Seo Won-Seon , Park Chan , Kim Il-Ho , Kim Sun-Uk
Published: October 2013

In order to obtain single-phase higher manganese silicides (HMS) and investigate the effect of sintering conditions on the thermoelectric properties of a HMS system, HMS compounds were synthesized using a vacuum induction melting method and sintered using spark plasma sintering (SPS) and hot pressing methods. Single-phase HMS with a small amount of second phases was obtained in all of the HMS samples produced. Changes in the electrical conductivity and Seebeck coefficient of the HMS were observed when the sintering temperature was changed, which can be attributed to the presence of the second phases. Similar changes of thermoelectric properties were observed in both the SPS and hot-pressed samples. However, the electrical conductivity and Seebeck coefficient of HMS samples (SPS-HMS) were higher than those of the hot-pressed samples, which can be attributed to SPS's shorter holding time and its ability to control the diffusion rate. The SPS-HMS sample sintered at 1123 K (1123 K SPS-HMS) had a higher figure of merit than any other sample although the sample had a lower power factor. The high value of the figure of merit of the sample can be attributed to its low thermal conductivity. The highest figure of merit value of 0.41 was measured at 850 K in the 1123 K SPS-HMS, which is comparable to the results reported earlier. The results of the present study can be used to optimize the fabrication process of HMS thermoelectric materials.
Effect of Ammonia Reaction Time on the Calytic Poperties of Sputtered Iron-Based Electrocatalyst
Authors: Lee Ki-Seong , Lee Minku , Hong Tae-Whan , Ju HyunChul , Kim Whangi , Kim Dongmin
Published: October 2013

Fe-based electrocatalysts for polymer electrolyte membrane fuel cells (PEMFCs) were produced using a sputter deposition process involving a carbon paper (CP) and a NH3 heat treatment environment. The Fe–N–CP sample reacted with ammonia for 10 min at 950 °C displayed a greater current density than the samples reacted with ammonia for other reaction times. The impedance of the samples treated for 10 min with ammonia shows the highest value, which means much higher ligand formation and lower electric conductivity, which are consistent with the results of cyclic voltammetry (CV). This is directly due to the formation of ligands between the Fe and CP used when exposed to a nitrogen environment. While the current density of the Fe-based electrocatalysts under review did not exceed that of standard Pt/C electrocatalysts, the results herein suggest that nonprecious metal electrodes may be a viable alternative in PEMFCs.
Growth and Electronic Structure Studies of Metal Intercalated Transition Metal Dichalcogenides MxNbSe2 (M: Fe and Cu)
Authors: Koh Yoonyoung , Cho Soohyun , Lee Joon , Yang Le-Xian , Zhang Yan , He Cheng , Chen Fei , Feng Dong-Lai , Arita Masashi , Shimada Kenya , Namatame Hirofumi , Taniguchi Masaki , Kim Changyoung
Published: October 2013

There has been renewed interest in transition metal dichalcogenides (TMDs) as electronic materials. The modification of the electronic structures of TMDs by means of metal intercalation would be of interest in that respect. With this motivation, we have synthesized and performed angle-resolved photoemission studies on Fe- and Cu-intercalated TMD Fe
x
NbSe2 and Cu
x
NbSe2 with various x values. Fe
x
NbSe2 (x = 0, 0.25) and Cu
x
NbSe2 (x = 0, 0.06) were grown by the iodine vapor transport method. Intercalation and doping were confirmed by changes in c-axis lattice constant and electronic structure, respectively. A significant amount of electron doping from Fe and Cu was observed, as indicated in the ARPES data measured as the rigid downshift of bands. In addition, band folding was observed in Fe
x
NbSe2, for which the unit cell is doubled owing to the Fe order. However, the extra band folding expected from the antiferromagnetic order of Fe was not observed.
Simplified Cu/Polyimide Damascene Approach Based on Imprint Process of Soluble Block Copolymer Polyimide
Authors: Park Sang-Cheon , Youn Sung-Won , Hiroshima Hiroshi , Takagi Hideki , Maeda Ryutaro , Kato Takahisa
Published: October 2013

In this study, a Cu/polyimide damascene approach based on an imprint technique was demonstrated aiming at developing a low-cost fabrication process for high-density interconnections in polyimide. First, a UV-assisted thermal imprint process that utilizes the high formability and low shrinkage of a soluble block copolymer polyimide was proposed as a high precision patterning process for polyimide. As a result, fine patterns (line widths ranging from 3 to 50 µm) with rectangular cross sections and clear line edges were fabricated in soluble block copolymer polyimide films by UV-assisted thermal imprinting followed by curing. Additionally, Cu damascene structures with a minimum line width of 3 µm were fabricated in the polyimide by performing subsequent Cu electroplating and chemical mechanical polishing (CMP), and the feasibility of the process was verified.
Silicon–Nitride-Passivated Bottom-Up Single-Electron Transistors
Authors: Hackenberger Guillaume , Azuma Yasuo , Kano Shinya , Tanaka Daisuke , Sakamoto Masanori , Teranishi Toshiharu , Ohno Yasuhide , Maehashi Kenzo , Matsumoto Kazuhiko , Majima Yutaka
Published: October 2013

We report the elaboration of SiN
x
-passivated chemically assembled single-electron transistors (SETs) by bottom-up processes involving electroless Au plating and the chemisorption of Au nanoparticles. With a Au top-gate electrode, the SiN
x
-passivated SETs showed a clear Coulomb diamond at 9 K and the top-gate capacitance was 17 times larger than the side-gate capacitance. Moreover, Coulomb oscillation and the Coulomb diamond were observed even at 160 K. Thus, planar technology is applicable to chemically assembled SETs.
Fabrication and Characterization of High-Mobility Graphene p–n–p Junctions Encapsulated by Hexagonal Boron Nitride
Authors: Masubuchi Satoru , Morikawa Sei , Onuki Masahiro , Iguchi Kazuyuki , Watanabe Kenji , Taniguchi Takashi , Machida Tomoki
Published: October 2013

We report on the fabrication and characterization of high quality graphene p–n–p junctions encapsulated by hexagonal boron nitride. By tuning the back gate and top gate bias voltages, a graphene p–n–p junction with tunable polarity and doping levels was realized. The p–n–p junction displayed distinct resistance oscillations, which was attributed to the Fabry–Perot interference of charge carriers in the p–n–p cavity. When a small magnetic field was applied, the oscillation phase was shifted by π, indicating the observation of Klein tunneling of charge carriers in the p–n–p junctions. The observation of Fabry–Perot interference and Klein tunneling with a macroscopic cavity length of L
c = 500 nm demonstrates the markedly high quality of our graphene p–n–p junction.
Self-Assembly and Reassembly Phenomena of Organic–Inorganic Hybrid Nanocrystals in Highly Ordered Nanocrystalline Multi/Monolayer
Authors: Hojo Daisuke , Togashi Takanari , Adschiri Tadafumi
Published: October 2013

Uniform and highly ordered nanocrystalline multilayers were obtained after tetrahydrofuran annealing of pre-assembled nanocrystals on the substrate surfaces. As a result of the rearrangement process during solvent annealing, cerium oxide hybrid nanocrystals were correctly positioned in the nanocrystalline film layers because of high carrier ability and the high affinity of the solvent to the nanocrystals. It was also found that solvent annealing had almost no effect on the nanocrystalline monolayer macroscopically, indicating that nanocrystals chemisorbed on the modified substrate surface did not move freely as compared with nanocrystals on top of the pre-assembled nanocrystals. A sufficiently highly ordered nanocrystalline structure was self-assembled in the concentrated solvent and thus printed to such a sticky surface from a face-down configuration that prevented the random deposition of nanocrystals, resulting in the uniform and ordered nanocrystalline monolayer of macroscopic size.
Normally-Off AlGaN/GaN High Electron Mobility Transistors with Thin and High Al Composition Barrier Layers
Authors: Zhang Kai , Mi Minhan , Chen Yonghe , Cao Mengyi , Wang Chong , Ma Xiaohua , Zhang Jincheng , Hao Yue
Published: October 2013

A GaN-based enhancement-mode high electron mobility transistor (HEMT) with a 1.5 nm GaN/9 nm Al0.65Ga0.35N thin barrier was reported. Without any treatment on barrier layer under the gate, the as-grown HEMTs exhibited a threshold voltage of 0.3 V, a maximum drain current density of 441 mA/mm at V
GS = 3 V and a peak extrinsic transconductance of 204 mS/mm at V
GS = 1.1 V. At the same time, both a low Schottky leakage current and an insignificant surface defects induced current dispersion were observed. Moreover, drain induction barrier lower (DIBL) effect was determined to be merely 3.28 mV/V at 1 mA/mm for a gate length of 0.5 µm. Additionally, post-gate annealing experiment at step temperatures up to 450 °C was implemented, only causing a minor shift in threshold voltage. These results demonstrated the substantial potential of thin and high Al composition barrier layers for high-voltage and highly reliable enhancement mode operation.
Improved Device Performance of GaN/AlGaN High-Electron-Mobility Transistor Using PdO Gate Interlayer
Authors: Lin Ray-Ming , Chu Fu-Chuan , Das Atanu , Liao Sheng-Yu , Su Vin-Cent
Published: October 2013

We demonstrate significant improvements of GaN/AlGaN high-electron-mobility transistors (HEMTs) by employing a PdO gate interlayer, which exhibit device performance superior to that of Pd Schottky gate HEMTs. The PdO gate interlayer effectively reduces the gate leakage current by four orders of magnitude, and it also increases the I
ON/I
OFF ratio to four orders of magnitude. The improved AlGaN/GaN/PdO HEMT shows a nearly ideal subthreshold slope of 66 mV/dec. The flicker noise characteristic is also observed to be lower in PdO-gate HEMTs than in Pd-Gate HEMTs. The high-work-function PdO layer and associated barrier height enhancement are the origins of the improved device performance.
Fabrication of Phase-Separated Benzoporphycene/[6,6]-Phenyl-C61-Butyric Acid Methyl Ester Films for Use in Organic Photovoltaic Cells
Authors: Saeki Hiroyuki , Misaki Masahiro , Kuzuhara Daiki , Yamada Hiroko , Ueda Yasukiyo
Published: October 2013

The crystallization behavior of benzoporphycene (BPc) converted from a thermoconvertible BPc precursor (BPc-pre) in the presence of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) was investigated. Upon annealing spin-coated films of BPc-pre and PCBM, BPc and PCBM crystallized individually to form a phase-separated structure. Repeated spin-coating of BPc-pre and PCBM in dichloromethane solution and subsequent annealing allowed the thickness of BPc films to be increased. BPc crystallized homoepitaxially on the underlying crystalline BPc layer after each deposition step. The thermal conversion conditions affected the size of BPc and PCBM crystals and the photovoltaic properties of the corresponding cells. An organic photovoltaic cell containing a repeatedly stacked BPc/PCBM film prepared by annealing at 250 °C for 1 min showed good rectification and a power conversion efficiency of 0.16%.
Fringe Field Effect on Electrical Characteristics of Pentacene Thin-Film Transistors
Authors: Park Jaehoon , Zhang Xue , Bae Moo-Ho , Park Gyeong-Tae , Bae Jin-Hyuk
Published: October 2013

This paper reports the effects of the fringe field on the operating characteristics of geometrically-modified pentacene thin-film transistors (TFTs) with a polymeric gate insulator. When the dimensions of the pentacene film structurally exceeded the channel region, the output current at a given voltage was overestimated by the extra charge carriers, which were affected by the fringe field in the peripheral territory away from the channel region. By examining the range of operating frequencies, the fringe field was found to have a much more serious effect at low frequencies due to the slow movement of charge carriers stored around the periphery of the patterned source and drain electrodes. This suggests that minimizing the fringe field is important for improving the dynamic characteristics of the organic transistor-based circuits operating at low frequencies.
Local Doping Modulation for Improving Quantum Efficiency in GaN-Based Light-Emitting Diodes
Authors: Wang Naiyin , Mei Ting , Yang Xiaodong , Li Hao , Zhu Ning , Zhang Minjie
Published: October 2013

Improvement of quantum efficiency (QE) in GaN-based light-emitting diodes is explored by engineering the band-edge profile with local doping modulation that leads to band bending due to the built-in electric field. Specifically, by p-type doping selected quantum well (QW) barriers, the overall Auger recombination rate can be suppressed due to more uniform carrier distributions, or electron leakage can be reduced due to greater effective barrier height of the electron blocking layer in the conduction band. Having doping modulation at several QW barriers, these two effects may be adopted in one structure combinatively. Physical mechanisms of performance improvement and the effects of p-type doping at different QW barriers are investigated detailedly.
New Formulas for Calculating the Lung‐to‐Head Ratio in Healthy Fetuses Between 20 and 40 Weeks' Gestation
Authors: Kehl Sven , Eckert Sven , Berlit Sebastian , Tuschy Benjamin , Sütterlin Marc , Siemer Jörn
Published: October 2013

Objectives

The purpose of this study was to develop new formulas for the expected fetal lung area‐to‐head circumference ratio in normal singleton pregnancies between 20 and 40 weeks' gestation.

Methods

The lung‐to‐head ratio and complete fetal biometric parameters of 126 fetuses between 20 and 40 weeks' gestation were prospectively measured. The lung‐to‐head ratio was measured by 3 different methods (longest diameter, anteroposterior diameter, and tracing). Formulas for predicting right and left lung‐to‐head ratios with regard to gestational age and biometric parameters were derived by stepwise regression analysis.

Results

New formulas for calculating right and left lung‐to‐head ratios by each measurement method were derived. The formulas included gestational age only and no biometric parameters.

Conclusions

The new formulas for estimating the expected lung‐to‐head ratio by the 3 different methods in normal singleton pregnancies up to 40 weeks' gestation may help improve the prognostic power of observed‐to‐expected lung‐to‐head ratio assessment in fetuses with congenital diaphragmatic hernias.