bluuebunny/crossref_metadata_2025 huggingface dataset:
Formation of Diamond-Like Carbon Thin Films by Using Surface Discharge Plasma under Atmospheric Pressure
Authors: Yasui Shinji , Hamada Hiroshi
Published: November 2013

The deposition of diamond-like carbon (DLC) thin films was conducted by using surface discharge plasma under atmospheric pressure. The high-frequency surface discharge plasma was generated by applying a pulsed voltage between electrodes. The main radicals generated by the surface discharge were H, CH, and C2by using H2, CH4, and He as plasma gases. The optical emission intensities of these radicals increased with increasing pulse width and decreasing pulse cycle of the applied pulse voltage. By increasing the length of the surface discharge, the ratios Hβ/Hαand C2/Hαincreased. It was demonstrated that a hard DLC film can be obtained at a lower deposition rate under the experimental conditions.
Characteristics of Sub-50 nm NAND Flash Devices with Various Self-Aligned Shallow Trench Isolation Depths
Authors: Yan Chin-Rung , Chen Jone F. , Lee Ya-Jui , Huang Wei-Shiang , Huang Meng-Ju , Chen Chih-Yuan , Lin Ying-Chia , Chang Kuei-Fen , Chen Huei-Haurng
Published: November 2013

The program efficiency and endurance characteristics of sub-50 nm NAND flash devices with various self-aligned shallow trench isolation (SA-STI) depths are investigated. Although a large SA-STI depth improves the neighboring floating gate coupling issue and gate coupling ratio, a low program efficiency is also introduced. In addition, lower endurance characteristics are observed in the device with a large SA-STI depth than in the device with a small SA-STI depth. The mechanisms underlying such unfavorable results are discussed on the basis of experimental data and technology computer-aided design simulations.
Plasma Diagnostics and Characterizations of Al-Doped ZnO Films Deposited with Low Temperature Sputtering Process
Authors: Choi Yoon S. , Shim Byeong C. , Kim Hye R. , Han Jeon G.
Published: November 2013

Facing targets sputtering (FTS) is known to be one of the promising magnetron sputtering systems for low temperature processes, because of the significant reduction of damage in the film structure, by the suppression of impinging high energy particles. In this study, FTS was compared with conventional magnetron sputtering (CMS), by various plasma diagnostics methods and film analysis. The sputtering target used was ZnO:Al (2%). OES was used to study the emission spectroscopy of process plasma. Ion current densities and the temperatures on the substrate were measured, to compare FTS with CMS. A coplanar-type Fabry–Perot interferometer (FPI) was utilized to measure the gas temperatures of Zn atoms, by Doppler broadening of the corresponding emission lines. Gas temperatures of Zn of FTS were measured to be lower, in the range of 200–300 K, compared with those of CMS. Film analysis showed that quality films can be synthesized at low temperature with rf powered FTS.
Effects of Nitrogen on Crystal Growth of Sputter-Deposited ZnO Films for Transparent Conducting Oxide
Authors: Suhariadi Iping , Oshikawa Kouichiro , Kuwahara Kazunari , Matsushima Kouichi , Yamashita Daisuke , Uchida Giichiro , Koga Kazunari , Shiratani Masaharu , Itagaki Naho
Published: November 2013

We have studied the effects of the N2 gas flow rate on the surface morphology of ZnO films deposited by the sputtering of a ZnO target using Ar/N2. Height-height correlation function (HHCF) analysis indicates that introducing a small amount of N2 (<5 sccm) to the sputtering atmosphere enhances adatom migration, leading to a larger grain size in the ZnO films associated with an increase in the lateral correlation length. The HHCF analysis also reveals that films deposited with and without N2 exhibit a self-affine fractal surface structure. We demonstrate that utilizing such ZnO films deposited using Ar/N2 as buffer layers, the crystallinity of ZnO:Al (AZO) films on the buffer layers can be greatly improved. The electrical resistivity of 100-nm-thick AZO films decreases from 1.8×10-3 to 4.0×10-4 Ω·cm by utilizing a ZnO buffer layers prepared at N2 flow rate of 5 sccm.
Annealing Effect on the Microstructure and Optical Characterization of Zn2SiO4 Thin Film Sputtered on Quartz Glass
Authors: Peng Kun-Cheng , Kao Hao-Che , Liu Shiu-Jen , Tsai Kuei-Lan , Lin Jing-Chie
Published: November 2013

A thin ZnO film (approximately 500 nm in thickness) was deposited on quartz glass by sputtering a ZnO target (purity of 99.995%) using a radio frequency (RF) power source in the magnetron sputter. Annealing of the specimen at elevated temperatures (i.e., 1000, 1100, and 1200 °C) was conducted to clarify the effects of annealing on the microstructure and optical characteristics of the film. It was found that silicon ions diffused faster than zinc and oxygen ions in the system containing the oxide film and quartz glass substrate Zn2SiO4 whose thickness depended on the annealing temperature and duration. The surface and cross-sectional morphologies of the as-sputtered film and films annealed at various temperatures were examined by field emission scanning electron microscopy (FE-SEM) and in more detail by high-resolution transmission electron microscopy (HRTEM). Line scans obtained by scanning transmission electron microscopy (STEM) showed that the composition (wt %) of the film annealed at 1200 °C was Zn (70%), Si (20%), and O (10%). These findings indicated that ZnO completely transferred into the Zn2SiO4 film to act as a luminescence center in the case of postannealing at 1200 °C for 2 h. The amounts of ZnO transferred to Zn2SiO4 were 38.5% at 1000 °C and 31.1% at 1100 °C for the same duration. The specimens annealed at 1000, 1100, and 1200 °C showed no photoluminescence (PL) emission as determined by measurement.
Plasma-Enhanced Reactive Magnetron Sputtering Assisted with Inductively Coupled Plasma for Reactivity-Controlled Deposition of Microcrystalline Silicon Thin Films
Authors: Takenaka Kosuke , Setsuhara Yuichi , Ebe Akinori
Published: November 2013

A plasma-enhanced reactive magnetron sputtering system with inner-type low-inductance modules has been developed. The properties of plasma sustained with inner-type low-inductance antenna (LIA) modules and the characteristics of silicon films deposited with a plasma-enhanced reactive sputter deposition system have been investigated. The results of plasma properties show that it is possible to control sputtering flux and reactivity independently via control target voltage and plasma density. Silicon films deposited by Ar + H2mixture plasma-enhanced reactive magnetron sputtering confirmed crystallization for a H2partial pressure (Rp) higher than 8% via XRD patterns and Raman spectra.
Plasma Processing of Functional Thin Films by Sputtering Deposition Using Metal-Based Powder Target
Authors: Kawasaki Hiroharu , Ohshima Tamiko , Ihara Takeshi , Arafune Kento , Taniyama Daichi , Yagyu Yoshihito , Suda Yoshiaki
Published: November 2013

Titanium-based functional thin films were prepared by a sputtering deposition method using a metal powder target, and the electron density and temperature of the processing plasma were investigated. The electron density of the plasma, measured by a probe method, when using a powder target was higher than that when using a bulk target. The deposition rate when using a powder target was also higher than that in the case of a bulk target. These results may be due to the net-cathode area of the powder target being larger than that of the bulk target. X-ray photoelectron spectroscopy, X-ray diffraction measurements, and atomic force microscopy images of the films prepared using the Ti powder target indicated nearly the same properties as those of films prepared using a Ti bulk target, and the prepared films are oxide. These results suggest that TiO2 thin films can be prepared using a Ti powder target and that the quality is almost the same as those of films prepared using a Ti bulk target.
Effect of Duty Cycle on Characteristics of CrNxThin Films Deposited by Pulsed Direct Current Reactive Magnetron Sputtering
Authors: Chang Chi-Lung , Wu Bo-Yi , Chen Pin-Hung , Chen Wei-Chih , Ho Chun-Ta , Wu Wan-Yu
Published: November 2013

CrNxthin films have been deposited on silicon wafer, 304 stainless steel, and tungsten carbide substrates using pulsed DC reactive magnetron sputtering. A 10 kHz unipolar mode and a N2/Ar ratio of 17.5% were used. During the deposition, the substrate was not biased and not heated during the entire deposition time of 30 min. The microstructure, crystalline phase, and mechanical properties of the obtained CrNxthin films were examined to investigate the effect of the duty cycle. The results show that the maximum current and power density increase with decreasing duty cycle from 100% (DC) to 5%. Although the thickness of the CrNxthin films decreases with decreasing duty cycle, the ratio of the thickness to the pulse on-time shows a maximum of 273.3 nm/min at the lowest duty cycle of 5%. The obtained CrNxthin films show a mixture of the Cr2N and CrN phases. Moreover, the Cr–N bonding state and the percentages of CrN and Cr2N vary with the duty cycle. The effects of the duty cycle on the hardness, coefficient of friction, and corrosion behavior of the CrNxthin films are also investigated in this study.
Properties of WO3-x Electrochromic Thin Film Prepared by Reactive Sputtering with Various Post Annealing Temperatures
Authors: Kim Min Hong , Choi Hyung Wook , Kim Kyung Hwan
Published: November 2013

The WO3-x
thin films were prepared on indium tin oxide (ITO) coated glass at 0.7 oxygen flow ratio [O2/(Ar+O2)] using the facing targets sputtering (FTS) system at room temperature. In order to obtain the annealing effect, as-deposited thin films were annealed at temperatures of 100, 200, 300, 400, and 500 °C for 1 h in open air. The structural properties of the WO3-x
thin film were measured using an X-ray diffractometer. The WO3-x
thin films annealed at up to 300 °C indicated amorphous properties, while those annealed above 400 °C indicated crystalline properties. The electrochemical and optical properties of WO3-x
thin films were measured using cyclic voltammetry and a UV/vis spectrometer. The maximum value of coloration efficiency obtained was 34.09 cm2/C for thin film annealed at 200 °C. The WO3-x
thin film annealed at 200 °C showed superior electrochromic properties.
Influence of Oxygen Addition and Wafer Bias Voltage on Bromine Atom Surface Reaction in a HBr/Ar Inductively Coupled Plasma
Authors: Iino Daiki , Nojiri Yasuhiro , Suzuki Keiji , Oike Takumi , Fujii Yoshitaka , Toyoda Hirotaka
Published: November 2013

The influence of the wafer surface material and wafer bias voltage on the Br radical density in HBr/Ar and HBr/Ar/O2 inductively coupled plasmas was investigated by appearance mass spectrometry. By increasing the bias voltage, a monotonic decrease in the Br radical density was observed irrespective of the surface material (Si, Al2O3) of the wafer. A drastic increase in Br radical density was observed after O2 addition to HBr/Ar plasma in the case of a bare Si wafer, whereas almost the same density was observed in the case of an Al2O3-sputtered Si wafer. X-ray photoelectron spectroscopy (XPS) analysis indicated that O2 addition promotes oxide formation on the Si surface. Measurement of the decay time constant for a Br radical after turning off the plasma indicated that O2 addition results in a longer decay time constant, suggesting the decrease of the surface loss probability of Br radicals for the surface-oxidized Si surface.
Spectroscopic Study and Motion Analysis of Arc Spot Initiated on Nanostructured Tungsten
Authors: Hwangbo Dogyun , Kajita Shin , Osaka Masashi , Ohno Noriyasu
Published: November 2013

Arcing on the nanostructured tungsten surface has been examined recently because it gives rise to the erosion of materials and impurity transport toward the core plasma in a nuclear fusion reactor. Arcing was initiated on a helium-exposed tungsten surface, on which nanostructured tungsten was formed, by irradiation with ruby laser pulses of 0.08 MJ·m-2. The motion of an arc spot was observed with a fast-framing camera. The magnetic field strength and arc current dependences of velocity were discussed on the basis of experimental observation. Arc trails were observed using a digital fine scope to determine the relationship between the grouping width of an arc trail and arc velocity; the changes in grouping width and condition of the specimen surface are discussed. Spectroscopic measurements were performed to determine the electron temperature by the Boltzmann plot method.
Analysis of Electron Temperature in DC Ar/SF6Plasma Using Cylindrical and Planar Probes
Authors: Kim Jin-Woo , Cho Soon-Gook , Bae Min-Keun , Kim Hyung-Jin , Chung Tae Hun , Chung Kyu-Sun
Published: November 2013

Electronegative plasmas are generated by adding SF6gas to a background argon (Ar) DC plasma with parameters ofn0= 1×1010cm3andTe= 2 eV. The heating current of the thoriated filament was in the range of 20.5–21.5 A and the plasmas were generated under a discharge condition of 100 V/0.4 A. The amount of negative ions was controlled by adjusting the ratio of flow rate of SF6= 0–10% to that of Ar. Plasma parameters were measured using cylindrical and planar electric probes. The behavior of electrons, which means the change in a parameter due to negative ion production, is characterized by measuring the floating and plasma potentials, and electron temperature. Electron temperature seems to increase and the potentials decrease with SF6flow rate.
Stable Molecules in N2–H2Plasmas Measured Using a Quartz Sensor
Authors: Suzuki Atsushi , Asahina Shuichi
Published: November 2013

Stable molecules of N2, H2, and NH3in N2–H2plasmas were investigated using a quartz sensor (Q-sensor). Changes in the pressure- and temperature-normalized Q-sensor output (NQO) induced by plasma with radio-frequency (rf) input power were measured near plasma electrodes and shown to correlate to the relative ion signal intensity from NH3. The results confirm that gas composition changes in N2–H2plasmas can be successfully measured from the NQO changes using the Q-sensor. The spatial distribution of NQO indicates that NH3molecules are produced near plasma electrodes rather than by secondary gas reactions in the plasma, which also means that Q-sensor measurements can provide information regarding stable gas molecules in plasma.
Sensitive Measurement of Trace Mercury Using Low Pressure Laser-Induced Plasma
Authors: Wang Zhenzhen , Deguchi Yoshihiro , Kuwahara Masakazu , Zhang Xiaobo , Yan Junjie , Liu Jiping
Published: November 2013

The emission of trace heavy metals, such as mercury (Hg), from power plants and other industries is a severe environmental problem concerning the public health. The laser-induced plasma technique was employed to measure Hg under various conditions, which reveals several merits of this method at low pressure. The main interferences of laser-induced breakdown spectroscopy (LIBS), which include the black-body-like emission from plasma itself and coexisting molecular and atomic emissions, decreased significantly using low pressure laser-induced plasma. Under low pressure conditions, Hg signal was rather clear without serious influence even if there is no delay time from the laser irradiation, which means the gated detection device is not necessary. This method featured the detection limit of 0.3 ppm at pressure 700 Pa. Additionally, the feasible of this method in real applications was demonstrated by measuring Hg in combustion gas which performed preferable results.
Simulation of Effective Production of Very High Frequency Hydrogen Plasma Using a Balanced Power Feeding Method
Authors: Ogiwara Kohei , Chen Weiting , Uchino Kiichiro , Kawai Yoshinobu
Published: November 2013

The characteristics of a VHF hydrogen plasma produced by a balanced power feeding method were examined by using a two-dimensional Monte Carlo fluid hybrid model. The simulation results showed that the electron density is maximum at a certain pressure between the discharge electrodes and significantly decreases outside the electrodes at a high gas pressure. The power absorption efficiency between the electrodes was improved by increasing the gas pressure. In addition, the plasma was produced efficiently between the electrodes at low applied voltages.
Removal of Water Pollutants by Pulsed Discharge Plasma and Observation of Its Optical Emission Intensity at Atmospheric Pressure
Authors: Hayashi Yui , Machmudah Wahyudiono , Kanda Hideki , Takada Noriharu , Sasaki Koichi , Goto Motonobu
Published: November 2013

Pulsed discharge plasma over the liquid surface was observed in the needle electrode configuration. The characteristics of streamer propagation including its optical emission intensity were investigated by using the intensified charge coupled device (ICCD) camera. The experiment was conducted at 313 K, 0.1 MPa argon in a batch-type reactor with methyl orange as a starting material. The characteristic of pulsed streamers were started from the electrode placed above the methyl orange liquid surface and then reached the methyl orange liquid surface, where they propagated on it. The propagation of pulsed streamers and their progression distance increased with the increase in peak voltage value. The optical emission intensity increased immediately after the breakdown; and it increased to its peak value when the applied voltage reached its peak value. After pulsed discharge plasma treatment, methyl orange degraded into its derived compounds with the appearance of light color. UV–vis spectrophotometer analyzed that the intermediate compounds from the degradation of methyl orange consist primarily of aromatic compounds which contain nitrogen functional groups. The degradation of methyl orange is 99% when the number of discharge plasma was 20000×. With increasing the pulse discharge numbers, the pH and the conductivity of methyl orange solution changed clearly.
Plasma Interactions with Organic Materials in Liquid through Plasma/Liquid Interface
Authors: Takenaka Kosuke , Setsuhara Yuichi
Published: November 2013

Plasma interactions with organic materials through the plasma/liquid interface as fundamental processes in plasma medicine have been investigated by degradation of methylene blue (MB) by irradiating with Ar/water mixture plasma. The optical emission spectra of Ar/water mixture plasma show considerable emissions of Ar lines, and the emission of H and OH radicals attributed to dissociation of water (H2O) in Ar/water mixture plasma has been confirmed. Variation in the molecular structure of MB in aqueous solution treated with the plasma has been observed by Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The results obtained from FT-IR and XPS analyses show that the Ar/water plasma exposure enables the degradation of organic materials in solution owing to oxidation by irradiated radicals from plasma through the plasma/liquid interface.
Plasma Surface Modification for Immobilization of Bone Morphogenic Protein-2 on Polycaprolactone Scaffolds
Authors: Kim Byung Hoon , Myung Sung Woon , Jung Sang Chul , Ko Yeong Mu
Published: November 2013

The immobilization of recombinant human bone formation protein-2 (rhBMP-2) on polycaprolactone (PCL) scaffolds was performed by plasma polymerization. RhBMP-2, which induces osteoblast differentiation in various cell types, is a growth factor that plays an important role in bone formation and repair. The surface of the PCL scaffold was functionalized with the carboxyl groups of plasma-polymerized acrylic acid (PPAA) thin films. Plasma polymerization was carried out at a discharge power of 60 W at an acrylic acid flow rate of 7 sccm for 5 min. The PPAA thin film exhibited moderate hydrophilic properties and possessed a high density of carboxyl groups. Carboxyl groups and rhBMP-2 on the PCL scaffolds surface were identified by attenuated total reflection Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, respectively. The alkaline phosphatase activity assay showed that the rhBMP-2 immobilized PCL scaffold increased the level of MG-63 cell differentiation. Plasma surface modification for the preparation of biomaterials, such as biofunctionalized polymer scaffolds, can be used for the binding of bioactive molecules in tissue engineering.
Treatment of Dipicolinic Acid and Inactivation Mechanism of Thermophile Spores Using Active Oxygen
Authors: Hayashi Nobuya , Kometani Ryo , Yoshida Yuki
Published: November 2013

The mechanism of the inactivation of thermophiles using active oxygen species concerning the destruction of the spore coat of thermophiles is proposed. The dependences of the light emission intensity of the excited oxygen molecule, the decomposition rate of the dipicolinic acid, and the inactivation rate of the thermophile on the oxygen gas pressure have similar tendencies. The inactivation mechanism is the decomposition of the dipicolinic acid in the spore coat by the excited oxygen molecule.
Mechanisms of Damage Formation during Rare Earth Ion Implantation in Nitride Semiconductors
Authors: Ruterana Pierre , Chauvat Marie-Pierre , Lorenz Katharina
Published: November 2013

The damage generated in wurtzite nitride semiconductors (AlN, GaN, and InN) by 300 keV rare earth ions has been studied following implantation at room temperature of Eu from 1012to above 1017ions/cm2. X-ray diffraction (XRD), transmission electron microscopy (TEM) and Rutherford backscattering (RBS) were used to investigate the evolution of damage and the deformation mechanisms versus the fluence. The behavior of the three compounds is clearly different; whereas InN breaks down at low fluences (∼1012ions/cm2), it is shown that the damage formation mechanisms are similar in AlN and GaN. In both compounds, extended defects such as stacking faults play a critical role but exhibit different stability, as a consequence, GaN transforms to nanocrystalline state from the surface at a fluence of around 2.5×1015ions/cm2. In contrast, AlN amorphizes starting at the projected range (Rp), when the fluence exceeds 1017ions/cm2.
Device Technology for GaN Mixed-Signal Integrated Circuits
Authors: Chen Kevin Jing , Kwan Alex Man Ho
Published: November 2013

A device technology platform for implementing GaN mixed-signal integrated circuits is presented. High-performance GaN enhancement-/depletion-mode (E/D-mode) high electron mobility transistors (HEMTs) are the key devices for implementing digital/analog functional blocks, while Schottky diodes and lateral field-effect rectifiers provide useful components for sensing circuits. As a case study, a GaN 2-bit quantizer circuit fabricated on that platform is demonstrated, leading a way to highly integrated system-on-chip solutions for protection/sense/control applications.
Silver Nanoparticles Obtained by Laser Ablation Using Different Stabilizers
Authors: Olea-Mejía Oscar , Pote-Orozco Héctor , Camacho-López Marco A. , Olea-Cardoso Oscar , López-Castañares Rafael , Vilchis-Néstor Alfredo R.
Published: November 2013

We have synthesized silver nanoparticles by laser ablation in water using three stabilizers: hexadecyltrimethylammonium (CTAB) surfactant, polyamidoamine dendrimer second generation (PAMAM 2G) and polyamidoamine dendrimer fourth generation (PAMAM 4G) at different concentrations. We obtained spherical nanoparticles with narrow size distributions and average sizes ranging from 6 to 20 nm depending on the type of stabilizer and its concentration. For all cases the highest stabilizer concentration yielded the lowest average particle size; 15.5, 9.5, and 5.6 nm for CTAB, PAMAM 2G and PAMAM 4G respectively. We have also studied the stability of the nanoparticle colloids over a period of 30 days. Only the colloids of CTAB 10-3 M, all the concentrations of PAMAM 4G and pure water were stable after this time. This is explained in terms of steric hindrance of the stabilizer molecules and particle charge from Zeta potential measurements. All the results from transmission electron microscopy correlate well with those observed from the ultraviolet and visible spectra of each sample in terms of absorbance, peak width and peak maximum.
Room-Temperature Fabrication of Au- and Ag-Incorporated Carbon Nanofibers by Ion Irradiation and Their Field Emission Properties
Authors: Yaakob Yazid , Yusop Mohd Zamri , Takahashi Chisato , Kalita Golap , Ghosh Pradip , Tanemura Masaki
Published: November 2013

We have demonstrated the growth of Au- and Ag-incorporated carbon nanofibers (CNFs) at room temperature by Ar+ bombardment on graphite surfaces with simultaneous Au and Ag supply. The evolution of their morphology and its effects on field emission properties were investigated. The structure and density of the grown CNFs depended on the metal supply rate. The ion-irradiated surfaces with excess metal supply featured sparsely distributed conical protrusions and a wall-like structure, while the surfaces irradiated with appropriate metal supply produced densely distributed CNF-tipped cones and a needlelike structure. Compared with Ag supply, Au supply yielded fewer CNFs in terms of number density. Thus, the CNF number density was controllable by adjusting the metal supply rate and metal species. A lower threshold field and a higher emission current density were achieved in the field emission of both metal-incorporated CNFs than of pristine CNFs (without metal incorporation). Thus, it is believed that metal-incorporated CNFs are promising for practical field emission device applications.
Semiconducting Properties of Nanostructured Amorphous Carbon Thin Films Incorporated with Iodine by Thermal Chemical Vapor Deposition
Authors: Kamaruzaman Dayana , Ahmad Nurfadzilah , Annuar Ishak , Rusop Mohamad
Published: November 2013

Nanostructured iodine-post doped amorphous carbon (a-C:I) thin films were prepared from camphor oil using a thermal chemical vapor deposition (TCVD) technique at different doping temperatures. The structural properties of the films were studied by field-emission scanning electron microscopy (FESEM), energy-dispersive spectroscopy (EDS), Raman, and Fourier transform infrared (FTIR) studies. FESEM and EDS studies showed successful iodine doping. FTIR and Raman studies showed that the a-C:I thin films consisted of a mixture of sp2- and sp3-bonded carbon atoms. The optical and electrical properties of a-C:I thin films were determined by UV–vis–NIR spectroscopy and current–voltage (I–V) measurement respectively. The optical band gap of a-C thin films decreased upon iodine doping. The highest electrical conductivity was found at 400 °C doping. Heterojunctions are confirmed by rectifying the I–V characteristics of an a-C:I/n-Si junction.
Microstructural Effect of Carbon Blacks for the Application in Lithium Ion Batteries
Authors: Yun Kang-Seop , Kim Bo-Ra , Noh Eul , Jung Hee-June , Oh Hyo-Jin , Kang Woo-Seung , Jung Sang-Chul , Myung Seung-Taek , Kim Sun-Jae
Published: November 2013

Carbon blacks commercially available (Super P, SP and Ketjen black, KB) and synthesized by a liquid phase plasma process (SC) were compared for the lithium ion battery applications as an anode material. All the carbon black samples were spherical with sizes in the range of 30–50 nm. The Brunauer–Emett–Teller (BET) specific surface areas of the SP, KB, and SC samples were measured to be 62, 1452, and 895 m2/g, respectively. The overall fraction of the ordered structure, represented by the ratio of the G-band to the D-band (G/D raio) from Raman spectra, was highest for the SC sample. A large specific surface area of the samples was found to play an important role in storing lithium ions, contributing to high initial charge capacities, 2050 mAh/g for KB and 1542 mAh/g for SC. The initial charge–discharge coulombic efficiency of the samples was strongly influenced by the solid electrolyte interface (SEI) formation behavior. The behavior of SEI formation seemed to be affected by the microstructural characteristics of the carbon blacks such as crystallinity and G/D ratio. The SC sample having a high G/D ratio and a slight variation without a peak of d
Q/d
V with potential showed a small initial capacity irreversibility.
Improvement on the Electron Transfer of Dye-Sensitized Solar Cell Using Vanadium Doped TiO2
Authors: Seo Hyunwoong , Wang Yuting , Ichida Daiki , Uchida Giichiro , Itagaki Naho , Koga Kazunori , Shiratani Masaharu , Nam Sang-Hun , Boo Jin-Hyo
Published: November 2013

In dye-sensitized solar cells, nanoporous structure of TiO2 is very important for efficient cell because lots of dye molecules are adsorbable and they are the source of the photocurrent. However, the internal impedance of TiO2 is relatively large and it limits the performance. For better performance, vanadium was doped into TiO2 in this work. Doping different material generally improves the characteristics and functions of original materials. Vanadium doping has some advantages such as the reduction of internal resistance, the improvement of chemical stability and high absorption. Especially, reduced internal resistance is so helpful for better electron transfer in TiO2 network. Various amounts of vanadium were applied and photovoltaic performance, internal impedance and absorbance were measured in order to verify the effect of vanadium doping. As a result, vanadium doping improved the overall performance from 6.01 to 6.81% with decreased internal resistance although adsorbed dye amount was reduced by decreased surface area and open circuit voltage was also decreased by the change of band-gap energy.
Hybrid Silicon Nanocrystal/Poly(3-hexylthiophene-2,5-diyl) Solar Cells from a Chlorinated Silicon Precursor
Authors: Ding Yi , Gresback Ryan , Yamada Riku , Okazaki Ken , Nozaki Tomohiro
Published: November 2013

Freestanding silicon nanocrystals (Si NCs) synthesized by a nonthermal plasma from silicon tetrachloride (SiCl4) were successfully employed in hybrid Si NC/poly(3-hexylthiophene-2,5-diyl) (P3HT) bulk-hetrojunction (BHJ) solar cells. The weight fraction of Si NCs in P3HT greatly influences device performance. As the weight fraction increases up to 50 wt %, short-circuit current dramatically increases, while open-circuit voltage (V
oc) and fill factor (FF) do not change significantly. The improvement in device performance is attributed to both increased probability of exciton dissociation in P3HT and an enhancement in the light conversion of wavelengths where P3HT is a poor absorber. These results demonstrate an alternative approach to synthesizing Si NCs from SiCl4 instead of silane (SiH4) for optoelectronic devices.
Epitaxial Growth of ZnInON Films with Tunable Band Gap from 1.7 to 3.3 eV on ZnO Templates
Authors: Matsushima Koichi , Hirose Tadafumi , Kuwahara Kazunari , Yamashita Daisuke , Uchida Giichiro , Seo Hyunwoong , Kamataki Kunihiro , Koga Kazunori , Shiratani Masaharu , Itagaki Naho
Published: November 2013

Epitaxial ZnInON (ZION) films with a tunable band gap have been successfully fabricated by RF magnetron sputtering on ZnO templates prepared via nitrogen mediated crystallization (NMC). X-ray diffraction (XRD) measurements show that the full widths at half maximum of the rocking curves from (002) and (101) planes are small at 0.10 and 0.08°, respectively, indicating a high crystallinity with good in-plane and out-of-plane alignments. Since the coherent growth of 35-nm-thick ZION films on NMC-ZnO templates is deduced from the reciprocal space mapping around the (105) diffraction, there is little lattice relaxation at the interface between the films and templates, which is significant in terms of the suppression of carrier recombination. The band gap of the ZION films has been tuned in a wide range of 1.7–3.3 eV by changing the Zn:In ratio. These results indicate that ZION is a potential absorption layer material of solar cells.
Tailoring Surface Properties of Polymeric Separators for Lithium-Ion Batteries by 13.56 MHz Radio-Frequency Plasma Glow Discharge
Authors: Liang Chia-Han , Juang Ruey-Shin , Tsai Ching-Yuan , Huang Chun
Published: November 2013

The hydrophilic surface modification of the polymeric separator is achieved by low-pressure 13.56 MHz radio-frequency Ar and He gas plasma treatments. The changes in surface hydrophilicity and surface free energy were examined by static contact angle analysis. The static water contact angle of the plasma-modified polymeric separator particularly decreased with the increase in treatment time. An obvious increase in the surface energy of polymeric separators owing to the crosslinking by activated species of inert gases effect of monatomic-gas-plasma treatments was also observed. Optical emission spectroscopy was carried out to analyze the chemical species generated after Ar and He gas plasma treatments. The variations in the surface morphology and chemical structure of the polymeric separators were confirmed by scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy (XPS) measurements. XPS analysis showed significantly higher surface concentrations of oxygen functional groups for monatomic-gas-plasma-modified polymeric separator surfaces than for the unmodified polymeric separator surface. The experimental results show the important role of chemical species in the interaction between Ar and He gas plasmas and the polymeric separator surface, which can be controlled by surface modification to tailor the hydrophilicity of the polymeric separator.
Analyses of Nematic Liquid Crystal Molecule Motion and Response Characteristics in Microstripline-Type Microwave Phase Shifter
Authors: Nguyen Thanh , Nguyen Bach Thanh , Ozaki Ryotaro , Moritake Hiroshi
Published: November 2013

In this paper, we propose an improved calculation method for analyzing the three-dimensional motion of nematic liquid crystal molecules in studies of all types of microwave transmission line loaded with a nematic liquid crystal. This method is applied to the analysis of motion of nematic liquid crystal molecules under a nonuniformly distributed electric field generated by asymmetric electrodes in a microstripline structure as a comprehensive example. Then, the dielectric constant distribution of the nematic liquid crystal layer, the effective dielectric constant in a microwave electric field, and the phase shift of a microwave in the microstripline loaded with a nematic liquid crystal are calculated. The rise time, decay time, and phase shift of a microwave phase shifter using a microstripline loaded with a nematic liquid crystal are also calculated. The differences in these response characteristics and their dependences on the width of the center conductor of the microstripline are determined by calculation and confirmed by performing experiments on the microwave phase shifters and an optical experiment on the retardation of the microstripline loaded with a nematic liquid crystal structure.
Surface Plasmon Resonance and Dielectric Core Effects on Two-Dimensional Periodic Arrays of Silver Nanospheres in a Square Lattice Embedded at Different Depths in a Silica Substrate
Authors: Sun Yuh-Sien , Jheng Ci-Yao
Published: November 2013

The dielectric core effects and surface plasmon resonance (SPR) modes of a two-dimensional (2D) periodic array of silver nanospheres (PASNSs) in a square lattice embedded at different depths in a silica substrate normally illuminated with thex-polarization plane wave are numerically investigated by using the finite element method with three-dimensional calculations. The unit cell of the 2D PASNSs examined is a unique structure, which is composed of a metallic nanoshell and a dielectric core (DC). Results show that the near-field optical properties and SPR modes obtained from the embedding cases of 2D PASNS are quite different from those of the solid cases of their counterpart, resulting in a field intensity increase and a redshift due to the plasmon hybridization of metallic nanoshells and their DCs. The strength of the hybridization depends on the geometry of the composite metallic nanoparticles and the surrounding media. On the basis of our simulations, we find two important parameters, i.e., the permittivity of the media filling DCs and the depth of the 2D PASNSs embedded in a silica substrate, which can affect the transmittance spectra and the position of SPR wavelengths. The intensity of transmittance spectra is reduced and the peak resonance is redshifted as the depth of the embedded 2D PASNSs is increased.
Mixing Effect of Gold and Silver Nanoparticles on Enhancement in Performance of Organic Thin-Film Solar Cells
Authors: Akiyama Tsuyoshi , Yamamoto Tomoki , Oku Takeo , Yahiro Masayuki , Kurihara Takashi , Adachi Chihaya , Yamada Sunao
Published: November 2013

Bulk-heterojunction organic thin-film solar cells incorporating gold and silver nanoparticles were fabricated and evaluated. These nanoparticles were embedded in the hole-transport layer of the solar cells. Plasmonic absorption peaks of isolated gold and silver nanoparticles were confirmed from extinction spectra even in the hole-transport material. The incorporation of gold and silver nanoparticles increased the photoelectric conversion efficiency of organic thin-film solar cells, whose enhancement ratio was further increased by mixing gold and silver nanoparticles.
Sub-Bandgap External Quantum Efficiency in Ti Implanted Si Heterojunction with Intrinsic Thin Layer Cells
Authors: Silvestre Santiago , Boronat Alfredo , Colina Mónica , Castañer Luis , Olea Javier , Pastor David , Prado Alvaro del , Mártil Ignacio , González-Díaz Germán , Luque Antonio , Antolín Elisa , Hernández Estela , Ramiro Iñigo , Artacho Irene , López Esther , Martí Antonio
Published: November 2013

In this work we present the manufacturing processes and results obtained from the characterization of heterojunction with intrinsic thin layer solar cells that include a heavily Ti ion implanted Si absorbing layer. The cells exhibit external circuit photocurrent at photon energies well below the Si bandgap. We discuss the origin of this below-bandgap photocurrent and the modifications in the hydrogenated amorphous intrinsic Si layer thickness to increase the open-circuit voltage.
Structure Analyses of Room Temperature Deposited AlOx Passivation Films for Crystalline Silicon Solar Cells
Authors: Sakai Chikako , Yamamoto Shunsuke , Urushibata Ko , Miki Shohei , Arafune Koji , Yoshida Haruhiko , Lee Hyun Ju , Ogura Atsushi , Ohshita Yoshio , Satoh Shin-ichi
Published: November 2013

We studied the structure of ozone-based atomic layer deposited aluminium oxide (AlO
x
) films as a passivation layer for p-type crystalline silicon (c-Si) solar cells and focused on the differences in the structure by the production conditions of AlO
x
films. Carbon (C)-related groups such as methyl, hydroxyl, and carboxyl groups which originate from the aluminium source, trimethylaluminium, were only found in the AlO
x
film deposited at room temperature (RT-sample). By post-deposition thermal annealing (PDA), the C-related groups were desorbed from the film and a part of their space remained as voids. The C-related groups were not found in the films deposited at 200 or 300 °C (heated-samples) since they were desorbed during the deposition. Even though C-related groups did not exist in the both RT- and heated-samples after PDA, the structure of the AlO
x
film of the RT-sample was different from that of the heated-sample.
Gain Spectral Filtering for Spectral Enhancement of Mode-Locked Fiber Oscillators
Authors: Hwang SungIn , Furuse Hiroaki , Haik Chosrowjan , Lim Changhwan , Kawanaka Junji , Miyanaga Noriaki
Published: November 2013

Spectral enhancement of a mode-locked fiber oscillator has been proposed by using gain spectral filtering technique. A wide spectral width of 83 nm at 1030 nm, with 5.2 nJ pulse energy was achieved with positive net cavity dispersion. Fiber oscillator output spectrum was analyzed numerically, showing larger gain spectral filtering effect in longer gain medium systems. We show that the gain spectral filtering plays the same role as spectral filter element inside the resonator, hence could replace it in dispersion managed lasers improving the output spectrum and simplifying fiber oscillator designs.
Novel Bulk Silicon Lateral Double-Diffused Metal–Oxide–Semiconductor Field-Effect Transistors Using Step Thickness Technology in Drift Region
Authors: Huang Shi , Guo Yufeng , Yao Jiafei , Hua Tingting , Zhang Jun , Zhang Changchun , Ji Xincun
Published: November 2013

In this paper, a novel bulk silicon lateral double-diffused metal–oxide–semiconductor field-effect transistors (LDMOS) using step thickness technology in drift region is proposed. The drift region is divided into several zones with different thicknesses increasing from source to drain. Owing to modulation effect of the step thickness drift region, new additional electric field peaks are introduced in the drift region, thus leading to the reduction of the surface electric fields and the increase of the breakdown voltage. The influences of device parameters on breakdown voltage and specific on-resistance are investigated using semiconductor device simulator, MEDICI. The simulation results indicate that an 18.4% increase in the breakdown voltage and a 42.5% increase in the figure of merit (FOM) are obtained in the novel device in comparison with the conventional LDMOS. Furthermore, single step can lead to approximately ideal FOM in comparison with the multiple steps, so that can obtain a suitable trade-off between fabrication costs and performance.
Enhancement of Valence Band Mixing in Individual InAs/GaAs Quantum Dots by Rapid Thermal Annealing
Authors: Harbord Edmund , Ota Yasutomo , Igarashi Yuichi , Shirane Masayuki , Kumagai Naoto , Ohkouchi Shunsuke , Iwamoto Satoshi , Yorozu Shinichi , Arakawa Yasuhiko
Published: November 2013

We measure polarization resolved photoluminescence from excitonic complexes in tens of single InAs/GaAs quantum dots (QDs) over a wide range of energies in two samples: one as-grown, the other subjected to rapid thermal annealing (RTA). Using the linear polarization of the X+emission as a probe of the valence band mixing (VBM), we find that RTA enhances QD VBM, attributed to the increase in QD height. We complement our measurements with 8-bandk·pcalculations, which suggest the increase in height on annealing is responsible for this enhancement.
Nondegradative Dielectric Coating on Graphene by Thermal Evaporation of SiO
Authors: Suzuki Seiya , Lee Chien-Chung , Nagamori Takashi , Schibli Thomas R. , Yoshimura Masamichi
Published: November 2013

The deposition of dielectric materials onto graphene without introducing atomic defects is challenging owing to the unavoidable exposure of carbon–carbon bonds to plasma, energetic ions, or high-energy photons that are present during deposition. Here, we report a simple and nondegradative method of depositing a silicon oxide layer on graphene based on the thermal evaporation of silicon monoxide (SiO). Raman spectroscopy and mapping showed that this method does not form defects in graphene, whereas depositing silicon oxide by e-beam evaporation severely damages graphene. The SiO-coated graphene also showed excellent resistance to ozone and hot air. Since SiO is transparent to visible light and infrared light, the coating may serve as a protective layer for graphene optical devices such as photodetectors and electro-optic modulators. Also noted that the present method is much simpler than atomic layer deposition, which requires additional functionalization of graphene.
Effect of MeV Electron Beam Irradiation on Graphene Grown by Thermal Chemical Vapor Deposition
Authors: Song Wooseok , Lee Su Il , Kim Yooseok , Jung Dae Sung , Jung Min Wook , An Ki-Seok , Park Chong-Yun
Published: November 2013

We explored the effect of MeV electron beam irradiation (MEBI) under ambient conditions on the growth of graphene by thermal chemical vapor deposition. X-ray photoelectron spectroscopy and Raman spectroscopy clearly revealed that the propagation of irradiation mediated-defects and oxidation on graphene transferred onto SiO2(300 nm)/Si(001) occurred simultaneously after MEBI. In addition, a positive shift in the charge-neutral Dirac point (CNDP) and suppression of electrical conductivity near the CNDP were observed by electrical transport measurements, indicating p-type doping and the opening of a band-gap of graphene after MEBI.
Theoretical Study on a Stable Structure and Hydrogen Adsorption of Hexagonal Boron Phosphide based on Density Functional Theory
Authors: Sato Kota , Sasaki Masakazu , Asano Haruka
Published: November 2013

A stable structure of hexagonal boron phosphide (BP) is theoretically studied using density functional theory and compared with that of hexagonal boron nitride (BN). In the case of BN, the stable structure is planar and the electron density of N is much higher than that of B, while in the case of BP, the stable structure is nonplanar and the electric charge is small. In the case of BP, the energy level of the lowest unoccupied molecular orbital (LUMO) is very low. Hydrogen adsorption on the boron and phosphine of BP is very exothermic. Stabilization is larger on boron than on phosphine. The second hydrogen adsorption is more exothermic than the first hydrogen adsorption. A nonplanar stable structure and high reactivity are considered to make hexagonal BP unstable.
Simulation of Fine Resist Profile Formation by Electron Beam Drawing and Development with Solubility Rate Based on Energy Deposition Distribution
Authors: Zhang Hui , Komori Takuya , Zhang Yulong , Yin You , Hosaka Sumio
Published: November 2013

We proposed a model for calculating the resist profile in electron beam drawing. The model predicts the solubility rate on the basis of the energy deposition distribution (EDD) for the development of latent patterns in the resist. By unifying the exposure doseD(via experiments) and EDDs (via calculations), we roughly determined solubility rates for three-dimensional EDDs, and established the proposed model. The development simulation was achieved by the sequential calculation method for solubility rates based on EDD which was calculated by Monte Carlo simulation. By determining a suitable EDD region to achieve good patterning, we obtained a sharp nanodot pattern of the resist. This simulation results are in good agreement with the experimental results obtained using a combination of 2.3 wt % tetramethylammonium hydroxide (TMAH) and 4 wt % NaCl as the developer. The model was demonstrated to be useful for predicting resist profiles with different experimental solubility rates of developers.
Oxynitride Formation Processes on Si(001) Studied by Means of Reflectance Difference Spectroscopy
Authors: Ohno Shin-ya , Mitobe Fumitake , Ochiai Toshiyuki , Suzuki Takanori , Tanaka Masatoshi
Published: November 2013

We investigated nitric oxide (NO) adsorption processes on Si(001) at temperatures of 110–873 K at a pressure of 1.0×10-5Pa by reflectance difference spectroscopy (RDS). The transition of the growth modes between Langmuir-type adsorption and two-dimensional oxide island growth was identified from the spectral line shape obtained with RDS, and from Arrhenius plots of the time constant for reaction in the growth of a monolayer oxynitride film. The decrease in the time constant at temperatures below 300 K compared to that at temperatures above 573 K suggested that trapping-mediated adsorption takes place at temperatures below 300 K.
Study of Temperature Behaviors for a Pellicle in Extreme-Ultraviolet Lithography: Mesh Structure
Authors: Kim In-Seon , Kim Ji-Won , Oh Hye-Keun
Published: November 2013

We report a theoretical study of the temperature behavior for a mesh structure of a pellicle in extreme-ultraviolet (EUV) lithography. Based on our modified heat transfer model, we calculate the temperature dependence of the pellicle mesh on the mesh materials and the structural parameters. The calculated results show that temperature change of the mesh is much slower than the thin film due to its high heat capacity and its saturation temperature has strong dependence on the material and the ratio of the cross-sectional area of the line to the side-cooling surface area of the mesh. Thermal damage is again minimal for the mesh support as is the case of a thin pellicle film.