bluuebunny/crossref_metadata_2025 huggingface dataset:
Capacitive Electron Cooling in an Inductively Coupled Plasma Source/Capacitively Coupled Plasma Bias Reactor
Authors: Jun Hyun-Su , Lee Dong-Seok , Chang Hong-Young
Published: October 2013

An electron cooling mechanism has been found in an inductively coupled plasma (ICP) source/capacitively coupled plasma (CCP) bias reactor. From the results of the measured electron energy probability function (EEPF), it was found that the temperature of low-energy electrons ε< 5 eV decreased with electron density when the bias power exceeded 100 W. In the case of a high-density plasma with an electron density of around 1011/cm3, capacitive coupling is a cause of significant ion loss, and electron wall loss is also enhanced to maintain the flux balance. Because of this flux balance, the potential barrier that must be overcome by electrons in the sheath collapse phase decreases further. This change in potential barrier enhances the wall loss of low-energy electrons below 5 eV, and the effective electron temperature decreases with an increase in bias power.
Bilayered Etch-Stop Layer of Al2O3/SiO2for High-Mobility In–Ga–Zn–O Thin-Film Transistors
Authors: Park Sang-Hee Ko , Kim Jong Woo , Ryu Min-Ki , Pi Jae-Eun , Hwang Chi-Sun , Yoon Sung-Min
Published: October 2013

We proposed a bilayered etch-stop layer (BiESL) composed of Al2O3/SiO2for the high-mobility oxide thin-film transistor (TFT) fabricated with low-resistivity Cu electrodes. The In–Ga–Zn–O TFT employing the BiESL showed no marked degradation in its high mobility and transfer characteristics even after the conventional passivation process using SiNxfilm, which causes hydrogen incorporation into the active channel. Excellent barrier properties of atomic-layer-deposited Al2O3film could provide the feasibility for the direct deposition of organic planarization film without the need for an extra passivation layer. The proposed BiESL structure was also suggested to be compatible with the simple patterning process of Cu electrodes.
Enhanced Electrical Properties of Novel Pb(Ni1/3Nb2/3)O3–BiScO3–PbTiO3Ternary System near Morphotropic Phase Boundary
Authors: Wang Dali , Jiang Zhaohua , Yang Bin , Zhang Shantao , Zhang Mingfu , Guo Feifei , Cao Wenwu
Published: October 2013

A novelxPb(Ni1/3Nb2/3)O3–(1-x)(0.30BiScO3–0.70PbTiO3) (PNN–BS–PT) ternary system was prepared by the columbite precursor method. The phase structure, microstructure, and electrical properties of ceramics of this system were investigated to identify the morphotropic phase boundary (MPB) composition of this system. The MPB with coexisting rhombohedral–tetragonal phases of PNN–BS–PT was located at approximatelyx=0.35, confirmed by their respective electric properties. With increasing PNN content, the coercive fieldEC, the Curie temperatureTC, and the rhombohedral-to-tetragonal phase transition temperatureTR–Twere found to decrease and showed nearly linear dependences on their compositions. The enhanced properties were achieved in the MPB composition withx=0.35, which are as follows: dielectric constant εr=3160 (1 kHz), piezoelectric coefficientd33=490 pC/N, and electromechanical coupling factorkp=0.44. In addition, a large bipolar strain on the order of 0.6% was achieved for the composition when an electrical fieldE=40 kV/cm was applied.
Photoluminescent Properties of Eu3+in Ga2O3:Cr3+Films Prepared by Metal Organic Deposition
Authors: Tokida Yoshinori , Adachi Sadao
Published: October 2013

We demonstrate the synthesis of β-Ga2O3:Eu3+red-emitting films by metal–organic deposition and report the photoluminescence (PL) properties of such films measured from 20 to 450 K. β-Ga2O3is one of five well-known modifications of gallium oxide. The X-ray diffraction analysis indicates that only β-phase Ga2O3can be synthesized by calcination atTc≥800 °C. An activation energy of ∼0.65 eV for the Eu3+ions in β-Ga2O3is determined from a plot of Eu3+-related red emission intensity vs calcination temperature. Lattice temperature dependences of the PL spectrum and luminescence decay time were performed atT= 20–450 and 20–300 K, respectively. No strong temperature dependences of the red emission intensity and decay time were observed below 300 K; however, the PL intensity atT> 300 K exhibited a gradual decrease with increasingT, yielding a quenching energy of ∼0.5 eV. The films calcined atTc≥900 °C revealed a deep-red emission band peaking at ∼1.7 eV, together with two sharp red emission peaks at ∼1.78 and ∼1.80 eV. These emission band and peaks were attributed to the Cr3+ions unintentionally doped in β-Ga2O3.
A Comparative Study on the Adsorption Behavior of Pentacene and Perfluoropentacene Molecules on Au(111) Surfaces
Authors: Lo Yuan-Yen , Chang Jung-Hung , Hoffmann Germar , Su Wei-Bin , Wu Chih-I , Chang Chia-Seng
Published: October 2013

In this study, we use low-temperature scanning tunneling microscopy and X-ray photoemission spectroscopy to study two closely related molecules, pentacene (PEN) and perfluoropentacene (PFP), adsorbed on a herringbone reconstructed Au(111) surface. PEN molecules are mobile under the probe tip at an elevated positive sample bias voltage with the direction of diffusion being correlated to the surface structure and the initial molecular orientation. Moreover, an induced rearrangement of the herringbone reconstruction is observable after manipulation. PFP molecules rearrange into flat, densely packed islands and the herringbone structure is undisturbed by the adsorbed PFP molecules. In addition, the X-ray photoelectron spectroscopy (XPS) C 1s and F 1s core level spectra of PFP show a shift toward high binding energy at high coverage. In comparison only a subtle shift for the C 1s core level of PEN at high coverage is seen. This indicates a different molecular arrangement for PFP in the bulk and in close proximity to the gold substrate.
Effect of Column Disorder on Carrier Transport in Columnar Discotic Liquid Crystal Evaluated by Applying Precisely Controlled Shear Stress
Authors: Kim Jaeki , Yamasaki Naoyuki , Hayashi Takeshi , Katayama Mitsuyoshi , Yoshida Hiroyuki , Moritake Hiroshi , Fujii Akihiko , Ozaki Masanori
Published: October 2013

The effect of column disorder on carrier drift mobility in columnar discotic liquid crystals has been investigated by applying a precisely controlled oscillating shear stress. Drift mobilities on the order of 10-1 cm2·V-1·s-1 were confirmed for positive and negative carriers in the columnar phase of 1,4,8,11,15,18,22,25-octahexylphthalocyanine in a well-aligned homeotropic geometry, in which the columnar axis was perfectly perpendicular to substrates with an electrode. A slight tilt of the columnar axis upon applying shear stress led to a marked decrease in electronic carrier mobility from 10-1 to less than 10-6 cm2·V-1·s-1, and transport was only confirmed for positive ion carriers. This result indicates that a uniform shear stress blocks the carrier transport path in the entire area of the electrode, and one-dimensional carrier transport path along the columns is easily hindered in columnar discotic liquid crystals.
Conversion Efficiency of Intermediate Band Solar Cells with GaAs:N δ-Doped Superlattices
Authors: Yagi Shuhei , Noguchi Shunsuke , Hijikata Yasuto , Kuboya Shigeyuki , Onabe Kentaro , Yaguchi Hiroyuki
Published: October 2013

The performance of intermediate band solar cells using a GaAs:N δ-doped superlattice (SL) as the optical absorber is analyzed. In GaAs:N δ-doped SLs, both of the E
+ and E
- bands formed around the N δ-doped layers form SL potentials with the conduction band of the spacer GaAs layers, resulting in the formation of multiple minibands. The conversion efficiency limits of the solar cells are calculated using the detailed balance model based on intermediate band structures composed of the valence band and two minibands formed respectively in the E
-- and E
+-related SL potentials. A high efficiency of 62.6% for full concentration is expected by properly adjusting the structural parameters of the SL. Alloying other elements such as In to a GaAs:N δ-doped SL is a possible way to further facilitate the development of intermediate band materials for high-efficiency solar cells.
Magneto-Optical Faraday and Kerr Effects in Topological Insulators Bi2Te3and Bi2Se3
Authors: Wang Xiao , Lian Jie , Huang Yue , Sun Zhaozong , Liu Junliang , Zhang Fujun , Gao Shang , Yu Xiaohong , Li Ping , Zhao Minglin
Published: October 2013

Three-dimensional topological insulator is a new quantum material which is insulating in the bulk but has current-carrying massless Dirac surface states. In this article, we investigate the magneto-optical properties of Bi2Te3and Bi2Se3. Our analysis shows that the Faraday rotation can be affected by the magnetic coupling strength. The peak position shows a hypochromic shift with increasing magnetic coupling strength. There are two giant Kerr rotations with one (-π/2) in the low-frequency area and the other one in the non-low-frequency area. The spectral range of Kerr rotation reduces with increasing film thickness, magnetic coupling strength and incident angle. For the Bi2Se3film, the giant Kerr rotation in the non-low-frequency area shows an obvious red shift. In addition, it is observed that the Faraday rotation peak position of Bi2Se3is the same as that of Bi2Te3, so the Faraday rotation can be only determined by magnetic coupling strength. The giant Kerr rotation spectral range in the non-low-frequency area is larger than that of Bi2Te3.
1/f Temperature Fluctuation Mechanism and Some Applications to Electronic Devices
Authors: Higuchi Hisayuki , Homma Noriyuki , Nakamura Tohru
Published: October 2013

A 1/ffluctuation mechanism based on a theorem that the mean square fractional fluctuation ΔN2/N2in a populationNof an ideal gas in diffusion that comes in contact with a heat reservoir equals 1/Nwas proposed and simulated on a computer. We observed the 1/fpower spectra in fluctuation waveforms. To confirm the simulated results, the origin of 1/ffluctuations was proven analytically and also the 1/ffluctuation spectrum of particles in the Brownian motion was verified experimentally. On the basis of the results, the 1/ffluctuations of temperature, resistance, and carrier recombination were formulated and compared with those of the experimental data. It was confirmed that the 1/ffluctuation mechanism could explain the experimental data quite well. The results also verified that the fluctuation due to the mobility fluctuation and the fluctuation due to the carrier density fluctuation were both explained well by the proposed fluctuation mechanism.
Effects of Fin Sidewall Angle on Subthreshold Characteristics of Junctionless Multigate Transistors
Authors: Lou Haijun , Li Dan , Dong Yan , Lin Xinnan , Yang Shengqi , He Jin , Chan Mansun
Published: October 2013

In this work, the subthreshold characteristics of a junctionless multigate transistor (JMT) with a trapezoidal fin cross section are studied by three-dimensional simulations. The effects of sidewall angle (Θ) on subthreshold swing (SS) and drain-induced barrier lowering (DIBL) are evaluated and compared with the effects of doping concentration. The results show that SS and DIBL are strongly dependent on Θ and more seriously affected by Θ variation. Meanwhile, as compared with those observed in inversion-mode multigate MOSFETs (IM-MuGFETs), the variations in SS and DIBL in JMTs with sidewall angle are better suppressed. A design guideline is finally proposed to define the optimal parameters of JMTs for a given technology.
Investigation of the Thermal Dissipation Characteristics of a Light-Emitting Diode Package Using Mold Surface Temperature
Authors: Kim Byung-Ho , Moon Cheol-Hee
Published: October 2013

To investigate the heat dissipation characteristics, we prepared three types of LED packages with different mold thicknesses: 0.7, 1.4, and 2.8 mm. The mold surface temperature (T
M) was measured with a thermocouple. An optimum solution for the heat dissipation model was realized using the variation of T
M versus mold thickness. Our results show that the rate of heat dissipation through the side wall of the ceramic package was increased from 0.11 to 0.26 W by increasing the mold thickness from 0.7 to 2.8 mm, which played a role in decreasing junction temperature (T
J) from 154 to 128 °C and T
M from 128 to 77 °C. This is in good agreement with the experimentally measured values of T
M. In the case of the 2.8-mm-thick mold, we determined that 35% of the total heat generated from the p–n junction of the LED chip dissipated through the side wall of the ceramic package.
Electrical Characteristics of Pt Schottky Contacts on AlInN:Mg/GaN Heterostructures
Authors: Kim Seongjun , Kim Hee Jin , Choi Suk , Ryou Jae-Hyun , Dupuis Russell D. , Ahn Kwang-Soon , Kim Hyunsoo
Published: October 2013

The electrical characteristics of Pt Schottky contacts on AlInN:Mg/GaN heterostructures were investigated. A barrier inhomogeneity model applied to temperature-dependent forward current–voltage (I–V) curves revealed the mean barrier height of 1.67 eV and the standard deviation of 0.22 eV. The reverse leakage current could be understood in terms of the Poole–Frenkel emission model, yielding the emission barrier height of 0.26 eV and the high-frequency relative dielectric permittivity of 5.32. On the basis of these obtained values, the continuum of electronic states could be predicted to locate 1.41 eV below the valence band.
Light Extraction Enhancement in AlGaInP-Based Vertical Light Emitting Diodes by Using Circular Micro-Contact Array
Authors: Seo Jae Won , Kim Yong Deok , Kwak Joon Seop
Published: October 2013

We have demonstrated that light output power of vertical AlGaInP-based light emitting diodes (LEDs) can be enhanced through use of a circular n+-GaAs/Ni/Ge/Au micro-contact array and an ITO current-spreading layer. We designed three different circular micro-contact arrays with different total areas and diameters for use as n-type electrodes in vertical AlGaInP LEDs. For comparison, LEDs with a normal linear-patterned n-type electrode were also fabricated. The results show that the circular micro-contact array for use an n-electrode in the vertical AlGaInP-based LEDs, greatly improved the uniformity of light output intensity, followed by increase in light output power. In addition, we also found that the total area of a circular micro-contact array and the thickness of the ITO current-spreading layer were important parameters for enhancing the light output power of the AlGaInP-based LEDs, due to a reduced light absorption in the circular micro-contact array and in the ITO layer.
Trap States of the Oxide Thin Film Transistor
Authors: Yu Kyeong Min , Yuh Jin Tae , Park Sang Hee Ko , Ryu Min Ki , Yun Eui Jung , Bae Byung Seong
Published: October 2013

We investigated the temperature dependent recovery of the threshold voltage shift observed in both ZnO and indium gallium zinc oxide (IGZO) thin film transistors (TFTs) after application of gate bias and light illumination. Two types of recovery were observed for both the ZnO and IGZO TFTs; low temperature recovery (below 110 °C) which is attributed to the trapped charge and high temperature recovery (over 110 °C) which is related to the annihilation of trap states generated during stresses. From a comparison study of the recovery rate with the analysis of hydrogen diffusion isochronal annealing, a similar behavior was observed for both TFT recovery and hydrogen diffusion. This result suggests that hydrogen plays an important role in the generation and annihilation of trap states in oxide TFTs under gate bias or light illumination stresses.
Numerical Simulation on the Charge Transport in Tris(8-hydroxyquinolinato)aluminum-Based Organic Light-Emitting Diode Structure
Authors: Kim Kwangsik , Won Taeyoung
Published: October 2013

In this paper, we report on our theoretical study on the charge transport of a multilayer structure for organic light-emitting diodes (OLEDs). Our simulation structure comprises a hole transport layer (HTL), an emission layer (EML), and an electron transport layer (ETL) between two electrodes wherein the HTL is N,N '-bis(3-methylphenyl)-N,N '-bis(phenyl)benzidine (TPD) and the ETL includes tris(8-hydroxyquinolinato)aluminum (Alq3). We discuss the carrier transport mechanism of the Alq3-based two-layer structure and thereby propose a high-efficiency device structure. We also report our investigation on the transient response during the turn-on/off period and the carrier transport in response to the variation of the injection barrier and applied voltage. This paper also reports the effect of the insertion of the EML layer and the efficiency dependence on the difference in the internal barrier height.
Effective Piezoelectric Area for Hitting-Type Piezoelectric Energy Harvesting System
Authors: Jung Hyun Jun , Song Daniel , Hong Seong Kwang , Song Yooseob , Sung Tae Hyun
Published: October 2013

The effective piezoelectric material area was determined by comparing data for different lengths of piezoelectric material on a substrate plate for a hitting-type piezoelectric module. Experimental results show that longer piezoelectric material lengths enable higher output power per unit volume. Further, as the piezoelectric material length increases, the maximum output power frequency increases and the matching impedance, or resistive load, decreases. In modeling the piezoelectric modules (cantilever beam), a UV resin coating was used to enhance the output power per unit volume in a hitting-type piezoelectric energy harvesting system. Comparison results of with UV and without UV coating showed that as the piezoelectric material length increases, UV coating has a greater effect on increasing the output power.
Fabrication of Diverse-Scale Patterned Layer on Organic Photovoltaics
Authors: Kim Yang Doo , Han Kang-Soo , Shin Ju-Hyeon , Ryu Mi Sun , Choi Kyung-woo , Lee Heon
Published: October 2013

In order to increase the conversion efficiency of organic photovoltaics (OPV), diverse-scale patterns were formed on a glass substrate using the direct printing technique. The optical properties of the patterns depended on the size, shape, height, and pitch of the patterns. Randomly distributed nano- and micro-patterns caused light scattering, which increased the diffusion transmittance. The other pattern, which was a nano-sized anti-reflective pattern comprising a 300 nm sized hexagonal array, decreased the reflectance of light on the surface. The optical properties of these patterns, can be used to improve solar cell efficiency by increasing the light allowed onto the light-absorbing layer. We used a direct printing method with a poly(dimethylsiloxane) (PDMS) mold to fabricate these patterns on glass substrates. These patterns were transferred from PDMS to the surface of a glass substrate. Hydrogen silsesquioxane (HSQ) was used as a resin since its properties include volatility and allow for spin-coating; it also has a reflective index similar to that of glass. This method has low cost and a simple process compared to optic-based lithography. After these patterns were formed outside the glass substrate, a conductive polymer layer and the active layer were formed by spin-coating, and the cathode was deposited by a thermal evaporator. The electrical properties of solar cells fabricated with these patterns on their surfaces were measured with a solar simulator. The conversion efficiency of the solar cells with these surface patterns showed an increase of up to 6.8% in comparison with conventional cells.
Influence of Different Annealing Ambients on the Properties of Zinc Sulfide Prepared by Atomic Layer Deposition
Authors: Yoo Dongjun , Heo Seung Chan , Choi Moon Suk , Kim Dohyung , Chung Chulwon , Choi Hag Young , Jeon Hyeongtag , Choi Changhwan
Published: October 2013

The effects of different post annealing ambients (vacuum, O2, and H2S gases) on the chemical, structural, and optical properties of zinc sulfide (ZnS) thin films prepared by atomic layer deposition (ALD) were investigated. Diethylzinc [DEZ, Zn(C2H5)2] and H2S gas were used as precursor and reactant gas, respectively. Compared to as-deposited 50-nm-thick ZnS film, the optical energy band gap (E
g) of ZnS annealed under vacuum and H2S conditions increased from 3.73 to 3.85 eV, while it decreased down to 3.23 eV for the O2 annealing case. The change in the E
g of the thicker ZnS is similar to that of the thinner ZnS case. This behavior is related to the change in the Zn to S ratio. The vacuum and H2S anneals increases the Zn/S ratio, leading to higher Zn interstitial defects or S vacancy sites in the films. X-ray diffraction analysis reveals that ZnS thin film has a preferred orientation of hexagonal wurtizte (002) and cubic zinc blend (111) at ∼28.2°, and its grain size changes in a range from 18.79 to 28.14 nm after annealing. However, for O2 annealing, the patterns of both the newly formed ZnO phase and the reduced ZnS phase appear at 34.04°. This result suggests that change in the composition and crystal structure during the process significantly affects the optical properties of ZnS thin film, which should be taken into consideration in searching for an alternative buffer layer for Cu2InGaSe(S)4 (CIGS) thin film solar cell systems.
Effect of the Molar Ratio of B2O3 to Bi2O3 in Al Paste with Bi2O3–B2O3–ZnO Glass on Screen Printed Contact Formation and Si Solar Cell Performance
Authors: Kim Bit-Na , Kim Hyeong Jun , Chang Hyo Sik , Hong Hyun Seon , Ryu Sung-Soo , Lee Heon
Published: October 2013

In this study, eco-friendly Pb-free Bi2O3–B2O3–ZnO glass frits were chosen as an inorganic additive for the Al paste used in Si solar cells. The effects of the molar ratio of Bi2O3 to B2O3 in the glass composition on the electrical resistance of the Al electrode and on the cell performance were investigated. The results showed that as the molar ratio of Bi2O3 to B2O3 increased, the glass transition temperature and softening temperature decreased because of the reduced glass viscosity. In Al screen-printed Si solar cells, as the molar ratio of Bi2O3 to B2O3 increased, the sheet electrical resistance of the Al electrode decreased and the cell efficiency increased. The uniformity and thickness of the back-surface field was significantly influenced by the glass composition.
Local Structural Analysis for Mn-Doped ZnO Dilute Magnetic Semiconductors
Authors: Yang Dong-Seok , Kang Hee Jae
Published: October 2013

The local structure around Mn atoms in 5 wt % Mn-doped ZnO thin films was investigated using extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES). Mn-doped ZnO exhibits strong magnetization (SM), weak magnetization (WM) and non magnetization (NM) depending on the bond angles between two Mn and one O, bond distances between Mn and O, and the degree of order of Mn atoms. We found in the EXAFS results that the bond angle formed in a Mn–O–Mn configuration to lead to ferromagnetism is 107.7° for Mn-doped ZnO thin films. Our results indicate that local structural variations have an influence on the determination of magnetic or nonmagnetic samples.
Effect of Bias Temperature Stress on the Anti-Reflection HfO2 Layer in Complementary Metal Oxide Semiconductor Image Sensors
Authors: Kim Hyung-Joon , Lee Kyung-Su , Choi Pyungho , Kim Kwang-Soo , Baek Dohyun , Choi Byoungdeog
Published: October 2013

The effects of various electrical characteristics of HfO2 in CMOS image sensors on bias-thermal stress instability were evaluated. In this work, the HfO2 dielectric layer was used as the anti-reflection layer of image sensors because it had negative charges and could electrically form a p+ layer on a silicon photodiode surface. After the HfO2 layer was stressed with electric field 0.5 MV/cm, 200 °C, and 10 min, there was severe electrical degradation such as +18.8 V flatband voltage shift. In order to investigate this degradation, the oxide trap charges and border trap charges of the HfO2 layer were measured and calculated. Based on these results, the interface trap density and minority carrier generation lifetime, which are directly related to the dark current in CMOS image sensors, were measured. The interface trap density degraded from 4.5×1011 to 1.0×1012 cm-1 eV-1 and the generation lifetime also degraded from 983 to 17 µs after stress application. This trap generated degradation model is suggested for CMOS image sensors. Therefore, pre-stabilization of bias-thermal stress should be implemented to use the HfO2 layer in modern CMOS image sensors.
Effects of Fabrication Errors on the Sensitivity of Nano-Replicated Guided Mode Resonance Protein Sensors
Authors: Cho Eikhyun , Kim Taekyung , Shin Ryung , Kim Myungyon , Cho Younggeol , Heo Youra , Kim Hokwan , Lim Jiseok , Kim Miroo , Jung Hyungil , Kim Seok-min , Kang Shinill
Published: October 2013

Although an injection molding is a promising method for inexpensive mass production of nanograting substrate for disposable guided mode resonance (GMR) protein sensor, the incomplete filling of nanocavities due to the thick solidified layer in conventional injection molding process may lower the sensitivity of label-free GMR protein sensor. In this study, an instant heating method at the filling stage during the injection molding process was investigated to improve the pattern transcribability of molded nanograting and the sensitivity of fabricated GMR protein sensor. Two types of injection molded nanograting with and without instant heating method were prepared and the effects of pattern fidelity on the performance of fabricated GMR protein sensor were analyzed by theoretical and experimental methods.
Effect of Dopant Concentration in Lightly Doped Drain Region on the Electrical Properties of N-Type Metal Induced Lateral Crystallization Polycrystalline Silicon Thin Film Transistors
Authors: Son Se Wan , Byun Chang Woo , Lee Yong Woo , Yun Seung Jae , Takaloo Ashkan Vakilipour , Park Jae Hyo , Joo Seung Ki
Published: October 2013

In this study, the effect of dopant concentration in lightly doped drain (LDD) region on the electrical properties of N-type gate insulator doping mask (GIDM) LDD metal-induced lateral crystallization (MILC) polycrystalline silicon thin film transistors (TFTs) was investigated. In order to find the optimum value for the dopant concentration in LDD region, we analyzed the electrical properties of LDD MILC TFTs with different dopant concentration in LDD region. The dopant concentrations in LDD regions of the TFTs were measured using secondary ion mass spectroscopy (SIMS). From the electrical properties and the SIMS data of the TFTs, it has been found that for the N-type GIDM LDD MILC TFTs with the LDD length of about 1.5 µm, the dopant concentration in LDD region should be in the range between 1019 and 3×1020/cm3 to ensure the suppression of off-state leakage current without device performance degradation.
Direct Electrical Detection of DNA Hybridization Based on Electrolyte-Gated Graphene Field-Effect Transistor
Authors: Ohno Yasuhide , Okamoto Shogo , Maehashi Kenzo , Matsumoto Kazuhiko
Published: October 2013

DNA hybridization was electrically detected by graphene field-effect transistors. Probe DNA was modified on the graphene channel by a pyrene-based linker material. The transfer characteristic was shifted by the negative charges on the probe DNA, and the drain current was changed by the full-complementary DNA while no current change was observed after adding noncomplementary DNA, indicating that the graphene field-effect transistor detected the DNA hybridization. In addition, the number of DNAs was estimated by the simple plate capacitor model. As a result, one probe DNA was attached on the graphene channel per 10×10 nm2, indicating their high density functionalization. We estimated that 30% of probe DNA on the graphene channel was hybridized with 200 nM full-complementary DNA while only 5% of probe DNA was bound to the noncomplementary DNA. These results will help to pave the way for future biosensing applications based on graphene FETs.
Closed Fluid Cell with Liquid-Sealing Mechanism for Stable and Flexible Operation of Liquid-Environment Atomic Force Microscopy
Authors: Asakawa Hitoshi , Katagiri Yukitoshi , Fukuma Takeshi
Published: October 2013

We have developed a closed fluid cell using the liquid-sealing mechanism for liquid-environment atomic force microscopy (AFM). In the developed cell, a liquid material is used for sealing, which prevents the evaporation of the imaging solution and hence provides a high stability in the measurements. In addition, the sealing liquid suppresses the transmission of the vibrations induced by the scanner, which enables atomic-scale imaging even with a closed fluid cell. Here, we present the atomic-resolution imaging of mica in liquid using the developed cell. Owing to the flexible structure of the sealing liquid, the mechanism can be integrated into a wide range of existing AFM systems and provides a high flexibility in the X
Y tip positioning and the sample size. Here, we demonstrate the nanoscale imaging of Cu wiring patterns at different locations in a large sample, where the tip position is moved by more than 1.5 mm without breaking the closed AFM cell.
Fermi-Level Tuning of Topological Insulator Thin Films
Authors: Aitani Masaki , Sakamoto Yusuke , Hirahara Toru , Yamada Manabu , Miyazaki Hidetoshi , Matsunami Masaharu , Kimura Shin-ichi , Hasegawa Shuji
Published: October 2013

Topological insulators are insulating materials but have metallic edge states with peculiar properties. They are considered to be promising for the development of future low energy consumption nano-electronic devices. However, there is a major problem: Naturally grown materials are not truly insulating owing to defects in their crystal structure. In the present study, we have examined the electronic structure and transport properties of topological insulator ultrathin Bi2Te3 films by angle-resolved photoemission spectroscopy and in situ transport measurements. To realize a truly bulk insulating film, we tried to tune the Fermi-level position using two methods. The first of these, i.e., changing the Si substrate temperature during film growth (350–450 K) to reduce the defects in the grown films, had some effect in reducing the bulk residual carriers, but we could not fabricate a film that showed only the surface states crossing the Fermi level. The second method we employed was to incorporate Pb atoms during film growth since Pb has one less electron than Bi. When the films were grown at around 350 K, we observed a systematic shift in the Fermi level and obtained a bulk insulating film, although it was not possible to move the Dirac point just at the Fermi level. The change in the measured film conductivity was consistent with the shift in the Fermi level and suggested the detection of the surface-state conductivity. For films grown at a higher substrate temperature (450 K), the Fermi level could be tuned only slightly and a bulk n-type film was obtained. Pb incorporation changes the shape of the Dirac cone, suggesting the formation of a stoichiometric ternary alloy of Bi, Pb, and Te, which is another topological insulator.
Properties of Molecular Nanojets in Different Solutions
Authors: Goto Masahiro , Sasaki Michiko , Kasahara Akira , Tosa Masahiro
Published: October 2013

Molecular nanojets generated by sub-nanosecond pulsed laser irradiation have been observed under different conditions such as in glucose–water solutions with different viscosities and in salt-water solutions with different concentrations. Time-resolved shadowgraphy imaging of the molecular nanojets under the different conditions was performed. The molecular nanojets were ejected through the center of a cavitation bubble, which was generated by pulsed laser irradiation of the liquid. The speed and shape of the molecular nanojets and the size of the cavitation bubble changed markedly with the conditions. The speed of a molecular nanojet can be controlled by changing of the viscosity of the glucose–water solution and the concentration of the salt-water solution.
Relation Between Oxidation Rate and Oxidation-Induced Strain at SiO2/Si(001) Interfaces during Thermal Oxidation
Authors: Ogawa Shuichi , Tang Jiayi , Yoshigoe Akitaka , Ishidzuka Shinji , Teraoka Yuden , Takakuwa Yuji
Published: October 2013

To experimentally verify the Si oxidation reaction model mediated by point defect (emitted Si atoms and their vacancies) generation due to oxidation-induced strain, real-time photoelectron spectroscopy using synchrotron radiation was employed to simultaneously evaluate the amount of oxidation-induced strained Si atoms at the SiO2/Si interface, oxidation state, and oxidation rate during oxidation on n-type Si(001) surfaces with O2 gas. It is found that both the oxidation rate and the amount of strained Si atoms at the completion of the first-oxide-layer growth decrease gradually with increasing temperature from 300 to 550 °C, where the oxide grows in the Langmuir-type adsorption manner. It is found that the interface strain and oxidation rate have a strong correlation. We discuss the reason for the oxide coverage and oxidation temperature dependences of interfacial strain from the viewpoint of the behavior of adsorbed oxygen during the first-oxide-layer growth.
Selective Oxidation of Amorphous Carbon Layers without Damaging Embedded Single Wall Carbon Nanotube Bundles
Authors: Choi Young Chul , Lim Seong Chu
Published: October 2013

Single wall carbon nanotubes (SWCNTs) were synthesized by arc discharge, and then purified by selective oxidation of amorphous carbon layers that were found to encase SWCNT bundles and catalyst metal particles. In order to remove selectively the amorphous carbon layers with SWCNTs being intact, we have systematically investigated the thermal treatment conditions; firstly, setting the temperature by measuring the activation energies of SWCNTs and amorphous carbon layers, and then, secondly, finding the optimal process time. As a consequence, the optimal temperature and time for the thermal treatment was found to be 460 °C and 20 min, respectively. The complete elimination of surrounding amorphous carbon layers makes it possible to efficiently disperse the SWCNT bundles, resulting in high absorbance of SWCNT-ink. The SWCNTs which were thermal-treated at optimized temperature (460 °C) and duration (20 min) showed much better crystallinity, dispersibility, and transparent conducting properties, compared with as-synthesized and the nanotubes thermal-treated at different experimental conditions.
Thermal Sensor Probe with a Si Resonator in a Cavity for Thermal Insulation
Authors: Inomata Naoki , Ono Takahito
Published: October 2013

A thermal sensor probe with a Si resonator in a cavity for thermal insulation was designed and fabricated to measure a heat from fluidic samples in an atmosphere. The resonant thermal sensor was isolated in a cavity in a probe to decrease a vibration damping and a heat loss to surrounding environments, which increased the thermal sensitivity. The heat from the sample at the probe tip was conducted via a heat guide into the resonator in the cavity. Characteristics of the sensor probe were evaluated in terms of a quality factor, a temperature coefficient of the resonant frequency of the resonator, and a frequency stability. Its thermal resolution was 0.3 °C. The measurement of the D-glucose concentration in a droplet was demonstrated from its temperature changes. Our sensor probe could access specific samples on a two-dimensional space and has a feasibility to accomplish highly sensitive thermal measurements without any vacuum equipment.
Challenges and Regulatory Considerations in the Acoustic Measurement of High‐Frequency (>20 MHz) Ultrasound
Authors: Nagle Samuel M. , Sundar Guru , Schafer Mark E. , Harris Gerald R. , Vaezy Shahram , Gessert James M. , Howard Samuel M. , Moore Mary K. , Eaton Richard M.
Published: October 2013

This article examines the challenges associated with making acoustic output measurements at high ultrasound frequencies (>20 MHz) in the context of regulatory considerations contained in the US Food and Drug Administration industry guidance document for diagnostic ultrasound devices. Error sources in the acoustic measurement, including hydrophone calibration and spatial averaging, nonlinear distortion, and mechanical alignment, are evaluated, and the limitations of currently available acoustic measurement instruments are discussed. An uncertainty analysis of acoustic intensity and power measurements is presented, and an example uncertainty calculation is done on a hypothetical 30‐MHz high‐frequency ultrasound system. This analysis concludes that the estimated measurement uncertainty of the acoustic intensity is +73%/−86%, and the uncertainty in the mechanical index is +37%/−43%. These values exceed the respective levels in the Food and Drug Administration guidance document of 30% and 15%, respectively, which are more representative of the measurement uncertainty associated with characterizing lower‐frequency ultrasound systems. Recommendations made for minimizing the measurement uncertainty include implementing a mechanical positioning system that has sufficient repeatability and precision, reconstructing the time‐pressure waveform via deconvolution using the hydrophone frequency response, and correcting for hydrophone spatial averaging.
Clinical Outcomes of Mild Isolated Cerebral Ventriculomegaly in the Presence of Other Neurodevelopmental Risk Factors
Authors: Ball John D. , Abuhamad Alfred Z. , Mason Janelle L. , Burket Jessica , Katz Elionora , Deutsch Stephen I.
Published: October 2013

Objectives

The purpose of this study was to evaluate neuropsychological test data in school‐aged children whose fetal sonograms revealed mild isolated cerebral ventriculomegaly without asymmetry of the lateral ventricles.

Methods

Nine of 52 children 6 years and older with sonographic evidence of mild isolated cerebral ventriculomegaly without asymmetry of the lateral ventricles were able to be recruited for follow‐up school‐aged neuropsychological testing. The children received a half‐day battery of neuropsychological tests, including the Wechsler Abbreviated Scales of Intelligence; Beery‐Buktenica Developmental Test of Visual Motor Integration, Fifth Edition; Wide Range Achievement Test, Fourth Edition; and Integrated Visual and Auditory Continuous Performance Test. Parents completed the Conners 3 Parent Short Form and the Personality Inventory for Children, Second Edition.

Results

In this small group, other risk factors for neurodevelopmental disorders were often present, including preterm birth, perinatal hypoxia, and a family history of psychiatric disease or substance abuse. Within this sample, the proportion of children with a pattern of test results showing poorer nonverbal intelligence than verbal intelligence scores and poorer math than reading performance, as well as meeting criteria for a diagnosis of attention deficit/hyperactivity disorder, was higher than the basal rates of these problems among children in general.

Conclusions

Particularly given the complexity of various factors affecting neurodevelopment, follow‐up neuropsychological evaluation is warranted in children with sonographic evidence of mild isolated cerebral ventriculomegaly without asymmetry of the lateral ventricle (eg, in the context of poor school performance).
Diagnostic Utility of Sonography and Correlation Between Sonographic and Clinical Findings in Patients With Carpal Tunnel Syndrome
Authors: Tajika Tsuyoshi , Kobayashi Tsutomu , Yamamoto Atsushi , Kaneko Tetsuya , Takagishi Kenji
Published: October 2013

Objectives

First, we investigated the accuracy of carpal tunnel syndrome diagnosis by comparing the cross‐sectional area of the median nerve measured at the level of proximal inlet of the carpal tunnel with that measured at the level of the distal radioulnar joint on sonography. Second, we evaluated the correlation between sonographic and neurophysiologic findings and clinical findings assessed by the Carpal Tunnel Syndrome Instrument of the Japanese Society for Surgery of the Hand (JSSH).

Methods

Fifty wrists in 34 patients and 81 wrists in 45 healthy volunteers were examined. The proximal cross‐sectional area and the difference (Δ) between the proximal and distal cross‐sectional areas were calculated for each wrist. Nerve conduction velocity tests were performed for all patients with carpal tunnel syndrome. The proximal, distal, and Δ cross‐sectional areas were compared for the two groups. We examined the correlation between the proximal, distal, and Δ areas, nerve conduction velocity findings, and JSSH scores in the patients.

Results

The diagnosis of carpal tunnel syndrome determined by the Δ cross‐sectional area was more accurate than the diagnosis determined by the proximal area on receiver operating characteristic curve analysis (P = .006). Statistically significant correlations were found between proximal area, Δ area, and nerve conduction velocity findings (proximal, r = 0.45; P = .0013; Δ, r = 0.44; P = .001). The proximal and distal areas were positively correlated with the JSSH symptom severity score (proximal, r= 0.39; P= .005; distal, r = 0.35; P = .014).

Conclusions

The cross‐sectional area method using sonography has excellent performance for diagnosing carpal tunnel syndrome. It was useful for measuring the proximal and distal cross‐sectional areas to evaluated the symptom severity and for calculating the Δ cross‐sectional area to assess motor nerve damage in patients with carpal tunnel syndrome.
Focused Renal Sonography Performed and Interpreted by Internal Medicine Residents
Authors: Caronia Jonathan , Panagopoulos Georgia , Devita Maria , Tofighi Babak , Mahdavi Ramyar , Levin Benjamin , Carrera Louis , Mina Bushra
Published: October 2013

Objectives

Intensivist‐performed focused sonography, including renal sonography, is becoming accepted practice. Whether internal medicine residents can be trained to accurately rule out renal obstruction and identify sonographic findings of chronic kidney disease is unknown. The purpose of this study was to test the ability of residents to evaluate for this specific constellation of findings.

Methods

Internal medicine residents were trained in a 5‐hour module on focused renal sonography evaluating renal length, echogenicity, hydronephrosis, and cysts on a convenience sample of medical ward, intermediate care, and medical intensive care unit patients. All patients underwent comprehensive sonography within 24 hours. The primary outcome was represented by the Fleiss κ statistic, which indicated the degree of interobserver agreement between residents and radiologists. Sensitivity, specificity, and positive and negative predictive values were calculated using the comprehensive radiologist‐read examination as the reference.

Results

Seventeen internal medicine residents imaged 125 kidneys on 66 patients. The average number of studies performed was 7.3 (SD, 6.6). Residents demonstrated excellent agreement with radiologists for hydronephrosis (κ = 0.73; P < .001; SE, 0.15; sensitivity, 94%; specificity, 93%), moderate agreement for echogenic kidneys (κ = 0.43; P < .001; SE, 0.13; sensitivity, 40%; specificity, 98%), and substantial agreement for renal cysts (κ = 0.61; P < .001; SE, 0.12; sensitivity, 60%; specificity, 96%). Residents showed sensitivity of 100% and specificity of 88% for identification of atrophic kidneys, defined as length less than 8 cm.

Conclusions

After a 5‐hour training course, medical residents accurately identified hydronephrosis and key sonographic findings of chronic kidney disease in a cohort of medical patients. Screening for hydronephrosis and renal atrophy can be performed by medical residents after adequate training.
Single‐Molecule Tracking Photoactivated Localization Microscopy to Map Nano‐Scale Structure and Dynamics in Living Spines
Authors: MacGillavry Harold D. , Blanpied Thomas A.
Published: October 2013

Super‐resolution microscopy has rapidly become an indispensable tool in cell biology and neuroscience by enabling measurement in live cells of structures smaller than the classical limit imposed by diffraction. The most widely applied super‐resolution method currently is localization microscopy, which takes advantage of the ability to determine the position of individual fluorescent molecules with nanometer accuracy even in cells. By iteratively measuring sparse subsets of photoactivatable fluorescent proteins, protein distribution in macromolecular structures can be accurately reconstructed. Moreover, the motion trajectories of individual molecules within cells can be measured, providing a unique ability to measure transport kinetics, exchange rates, and binding affinities of even small subsets of molecules with high temporal resolution and great spatial specificity. This unit describes protocols to measure and quantify the distribution of scaffold proteins within single synapses of cultured hippocampal neurons, and to track and measure the diffusion of intracellular constituents of the neuronal plasma membrane. Curr. Protoc. Neurosci. 65:2.20.1‐2.20.19. © 2013 by John Wiley & Sons, Inc.
Structure downdip of deep low‐frequency earthquakes in western Shikoku, Japan, revealed by P and S waves propagating at slow apparent velocities from intraslab earthquakes
Authors: Kuge Keiko
Published: October 2013

For P waves traveling downdip of deep low‐frequency earthquakes (LFEs) from intraslab earthquakes in western Shikoku, Japan, we observed distinct later arrivals with slow apparent velocities comparable to velocities of the lower crust. The apparent velocities of predominant S waves were also in the range of lower crust speeds. Such observations suggest that the low‐velocity oceanic crust connects with the island arc crust beneath the western Seto Inland Sea, which may be due to direct contact or the presence of low‐velocity wedge mantle between the crusts. As high‐velocity mantle is not likely near deep LFEs in the region, deep LFEs occur either at the crust‐crust boundary or at the boundary between the oceanic crust and the overriding low‐velocity mantle. Observations of later arrivals differed between earthquakes in eastern and western Shikoku, implying that the location of the high‐velocity mantle can vary and affect temperatures along the zone where deep LFEs occur.
Quantitative comparison of methods for predicting the arrival of coronal mass ejections at Earth based on multiview imaging
Authors: Colaninno R. C. , Vourlidas A. , Wu C. C.
Published: October 2013

We investigate the performance of six methods for predicting the coronal mass ejection (CME) time of arrival (ToA) and velocity at Earth using a sample of nine Earth‐impacting CMEs between March 2010 and June 2011. The CMEs were tracked continuously from the Sun to near Earth in multiviewpoint imaging data from STEREO Sun‐Earth Connection Coronal and Heliospheric Investigation (SECCHI) and SOHO Large Angle and Spectroscopic Coronagraph (LASCO). We use the Graduate Cylindrical Shell model to estimate the three‐dimensional direction and height of the CMEs in every image out to ∼200R⊙. We fit the derived three‐dimensional (deprojected) height and time (HT) data with six different methods to extrapolate the CME ToA and velocity at Earth. We compare the fitting results with the in situ data from the Wind spacecraft. We find that a simple linear fit above a height of 50R⊙ gives the ToA with an error ±6h for seven (78%) of the CMEs. For the full sample, we are able to predict the ToA to within ±13h. These results are a half day improvement over past CME arrival time methods that only used SOHO LASCO data. We conclude that heliographic height‐time measurements of the CME front made away from the Sun‐Earth line and beyond the coronagraphic field of view are sufficient for reasonably accurate predictions of their ToA.