bluuebunny/crossref_metadata_2025 huggingface dataset:
A Novel Grinding Technique for 4H-SiC Single-Crystal Wafers Using Tribo-Catalytic Abrasives
Authors: Kido Takanori , Nagaya Masatake , Kawata Kenji , Kato Tomohisa
Published: February 2014

Diamond abrasives are generally used to machine silicon carbide (SiC) single crystals because of the high hardness of those crystals. Although Chemo-Mechanical Polishing (CMP) employs abrasives softer than the SiC single crystals together with oxidizing agents in order to avoid mechanical damage to the surface of SiC single-crystal wafers, none has reported so far the use of abrasive wheels other than diamond for grinding large SiC single-crystal wafers. The current study revealed that a novel grinding technique using non-diamond abrasives such as ceria (CeO2) can efficiently machine large SiC single-crystal wafers of 100 mm in diameter due hypothetically to the nature of newly named tribo-catalytic abrasives, and is promising to minimize the surface damage prior to the final CMP step.
Multi-Wire Electrical Discharge Slicing for Silicon Carbide Part 2: Improvement on Manufacturing Wafers by Forty-Wire EDS
Authors: Itokazu Atsushi , Miyake Hidetaka , Hashimoto Takashi , Fukushima Kazuhiko
Published: February 2014

In this paper, a machining energy control slicing method for cylindrical shaped ingots and forty-wire electrical discharge slicing (EDS) technology are investigated. Our recent study in [4], ten-wire EDS was applied to 100 mm-square polycrystalline SiC material. Applying this technology to ingot slicing, an appropriate process technology for cylindrical shaped SiC materials which are the same as an actual ingot is required. The slicing of cylindrical shaped SiC using conventional multi-wire EDS causes the increase of sori, or wire break with unstable machining process since wasteful machining power is not controlled as a function of machining length. To resolve this problem, we applied the machining energy control method which varies machining power with machining position. Using proposed method, ten-simultaneous slicing of cylindrical shaped SiC material is obtained with 80 μm/min in machining speed. The sori of machined surface is 34 μm, and TV5 is 28 μm as a result. Moreover, forty-wire EDS technology is applied to SiC slicing for improving wafer productivity. We successfully verified forty-simultaneous slicing of 100 mm-square poly-crystal SiC material without wire break. The sliced 39 thin plates are obtained 385 μm in average thickness, and 16 μm in maximum thickness variation.
Development of Multi-Wire Electric Discharge Machining for SiC Wafer Processing
Authors: Ogawa Masumi , Mine Kei , Fuchiyama Seiki , Tawa Yasuhiro , Kato Tomohisa
Published: February 2014

In order to slice the larger size ingot toward 6 inch of silicon carbide (SiC), we are developing Multi-wire Electric Discharge Machining (EDM). To prevent wire break during slicing, we have developed the electric discharge pulse control system. So far, with 10 multi-wires, we have succeeded in slicing of 4 inch SiC balk single crystal without wire break. High quality slicing surface (e.g. small value of around 10 μm of SORI for 3 inchi wafer) was also achieved. By polishing methode, EDM-sliced wafer was estimated to have the uniform thickness of damaged layer over the entire surface. We confirmed that the wafer sliced by EDM can be processed in the later process, by grinding the 3 inch wafer. And it was confirmed that 6 inch ingot can be sliced with 10 multi-wire EDM, by slicing the boule of SiC poly crystal. For the larger diameter ingot than 4 inch, Multi-wire EDM will be practically used by the effective removal of machining chips from the machining clearance between the wire and work.
Fabrication of Electrostatically Actuated 4H-SiC Microcantilever Resonators by Using n/p/n Epitaxial Structures and Doping-Selective Electrochemical Etching
Authors: Sato Kosuke , Adachi Kohei , Okamoto Hajime , Yamaguchi Hiroshi , Kimoto Tsunenobu , Suda Jun
Published: February 2014

We fabricated electrostatically actuated single-crystalline 4H-SiC microcantilever resonators. To realize a narrow gap between cantilevers and substrate, we etched a thin p-type SiC layer in n/p/n multilayer structure by doping-selective electrochemical etching. The resonant characteristics of the fabricated 4H-SiC microcantilevers were investigated under a vacuum condition. Electrostatic actuation of microcantilevers was successfully performed by applying 10 mVrms ac voltage with 20 mV dc bias. The quality factor of 4H-SiC microcantilevers was above 100,000, which is about ten times higher than the quality factor of Si cantilevers with the same structure. Resonant characteristics were almost identical for mechanical actuation and electrostatic actuation.
Designing and Fabrication of the VLD Edge Termination for 3.3 kV SiC SBD
Authors: Ebihara Kohei , Yamamoto Yasuki , Nakaki Yoshiyuki , Aya Sunao , Nakata Shuhei , Imaizumi Masayuki , Toyoda Yoshihiko , Yamakawa Satoshi
Published: February 2014

Edge termination guaranteeing high breakdown voltage and robustness in its fabrication are required in SiC power devices. We newly employed the VLD edge termination for 3.3 kV-rated SiC SBDs, which was formed by Al ion implantation using a resist mask having a varying thickness. The breakdown voltage is recorded to be over 96% of the parallel-plane breakdown voltage, and the reverse bias characteristics are well accorded with the result of TCAD simulation.
Study of 4H-SiC Schottky Diode Designs for 3.3kV Applications
Authors: Bartolf Holger , Sundaramoorthy Vinoth , Mihaila Andrei , Berthou Maxime , Godignon Philippe , Millan José
Published: February 2014

The static performance of different active and termination area designs for SiC-based Schottky diodes, suitable for 3.3kV applications, were investigated by means of extensive numerical simulations. We found quantitatively that the high electric field of SiC close to avalanche-breakdown is shielded most effectively from the Schottky interface by a trench-based design. Moreover, we conclude that the edge termination design with junction termination extension and four implanted p+ guard rings is most robust against oxide interfacial charge.
Simulation, Fabrication and Characterization of 4500V 4H-SiC JBS Diode
Authors: Huang Run Hua , Chen Gang , Bai Song , Li Rui , Li Yun , Tao Yong Hong
Published: February 2014

4H-SiC JBS diode with breakdown voltage higher than 4.5 kV, has been successfully fabricated on 4H-SiC wafers with epitaxial layer. In this paper we report the design, the fabrication, and the electrical characteristics of 4H-SiC JBS diode. Numerical simulations have been performed to select the doping level and thickness of the drift layer and the effectiveness of the edge termination technique. The epilayer properties of the N-type are 55 μm with a doping of 9×1014 cm−3. The diodes were fabricated with a floating guard rings edge termination. The on-state voltage was 4V at JF =80 A/cm2
Properties of a SiC Schottky Barrier Diode Fabricated with a Thin Substrate
Authors: Nakanishi Yosuke , Tominaga Takaaki , Okabe Hiroaki , Suehiro Yoshiyuki , Sugahara Kazuyuki , Kuroiwa Takeharu , Toyoda Yoshihiko , Yamakawa Satoshi , Murasaki Hiroyuki , Kobayashi Kazuo , Sumitani Hiroaki
Published: February 2014

One of the attractive methods to reduce the differential resistance of SiC devices is to make the thickness of a SiC substrate thinner [1]. Therefore, we fabricated SiC Schottky barrier diode (SBD) chips with a thickness below 150 μm and the properties of the SiC-SBD chips were measured. It was confirmed that the junction temperature of the thin SiC-SBD chips was decreased by the combination of the reduction in a thickness of the chip and the back side bonding of the chip using a material with high thermal conductivity. Moreover, it was confirmed that the potential of the thin SiC-SBD chip for the surge current capacity could be enhanced to combine the thin SiC-SBD chip with the back side bonding which has high thermal conductivity.
4H-SiC Diode Avalanche Breakdown Voltage Estimation by Simulation and Junction Termination Extension Analysis
Authors: Rong Hua , Sharma Yogesh K. , Li Fan , Jennings Michael R. , Mawby Philip  Andrew
Published: February 2014

This paper presents and compares different avalanche breakdown voltage estimation methods in 4H-SiC (silicon carbide) using finite element simulation results on Schottky diode. 4H-SiC avalanche breakdown voltage and depletion width estimated with Baligas equations have shown to be higher than other estimation techniques and simulation results, especially for voltages higher than 5kV. This paper discusses the impact of choosing different junction termination extension (JTE) structures on two-dimensional junction curvature effects and electric field crowding for Schottky diodes Space-Modulated JTE (SMJTE) structure with optimum JTE dose and dimension could achieve up to 90% of the parallel plane breakdown voltage. For ultra high voltage devices (>15 kV) the SMJTE has significant improvement in terms of breakdown voltage. It also has a wider optimum JTE dose window. For 1 kV device there is not a significant difference in breakdown voltage between JTE and SMJTE structures.
Ultrahigh-Voltage (> 20 kV) SiC PiN Diodes with a Space-Modulated JTE and Lifetime Enhancement Process via Thermal Oxidation
Authors: Kaji Naoki , Niwa Hiroki , Suda Jun , Kimoto Tsunenobu
Published: February 2014

Ultrahigh-voltage SiC PiN diodes with an original junction termination extension (JTE) structure and improved forward characteristics are presented. A space-modulated JTE (SM-JTE) structure was designed by device simulation, and a high breakdown voltage of 26.9 kV was achieved by using a 270 μm-thick epilayer and 1050 μm-long JTE. In addition, lifetime enhancement process via thermal oxidation was performed to improve the forward characteristics. The on-resistance of the SiC PiN diodes was remarkably reduced by lifetime enhancement process. The temperature dependence of the on-resistance was also discussed.
VF Degradation of 4H-SiC PiN Diodes Using Low-BPD Wafers
Authors: Ota Chiharu , Nishio Johji , Takao Kazuto , Shinohe Takashi
Published: February 2014

In this paper, we found origin of VF degradation of SiC bipolar devices other than a basal plane dislocation (BPD) in the SiC substrate. A VF degradation of the 4H-SiC PiN diodes with low-BPD wafers was evaluated and its origins were discussed. Some diodes suffered VF degradation, even though they were fabricated on BPD-free area. PL mapping, TEM image, and optical observation after KOH etching showed that there were Shockley stacking faults and combined etch-pits arrays, which were presumed to be caused by the device process.
13-kV, 20-A 4H-SiC PiN Diodes for Power System Applications
Authors: Okamoto Dai , Tanaka Yasunori , Mizushima Tomonori , Yoshikawa Mitsuru , Fujisawa Hiroyuki , Takenaka Kensuke , Harada Shinsuke , Ogata Shuji , Hayashi Toshihiko , Izumi Toru , Hemmi Tetsuro , Tanaka Atsushi , Nakayama Koji , Asano Katsunori , Matsumoto Kazushi , Ohse Naoyuki , Ryo Mina , Ota Chiharu , Takao Kazuto , Mizukami Makoto , Kato Tomohisa , Takei Manabu , Yonezawa Yoshiyuki , Fukuda Kenji , Okumura Hajime
Published: February 2014

We successfully fabricated 13-kV, 20-A, 8 mm × 8 mm, drift-free 4H-SiC PiN diodes. The fabricated diodes exhibited breakdown voltages that exceeded 13 kV, a forward voltage drop of 4.9–5.3 V, and an on-resistance (RonAactive) of 12 mW·cm2. The blocking yield at 10 kV on a 3-in wafer exceeded 90%. We investigated failed devices using Candela defect maps and light-emission images and found that a few devices failed because of large defects on the chip. We also demonstrated that the fabricated diodes can be used in conducting high-voltage and high-current switching tests.
Comparison of 5kV SiC JBS and PiN Diodes
Authors: Berthou Maxime , Godignon Philippe , Calvo Jose , Mihaila Andrei , Bianda E. , Nistor Iulian
Published: February 2014

Recent availability of large SiC wafer with reduced density of defects and maturity of our fabrication process permitted to fabricate 15A-5kV W-JBS (25 mm2) and 15A-5kV PiN (10 mm2) diodes on 4 wafers. We will present and compare their static characteristics. Several W-JBS diodes have been packaged and switched at 2.5kV to study their reverse recovery and demonstrate the major advantages of the SIC-JBS devices at high voltage.
650V SiC JFET for High Efficiency Applications
Authors: Bergner Wolfgang , Rupp Roland , Kirchner Uwe , Kueck Daniel
Published: February 2014

This paper presents for the first time a 650V SiC JFET switch. Although this application class is highly competitive and occupied by Silicon devices the characterization data show unique features which make the SiC switch an outstanding option for future system integration.
Gate-Drive Voltage Design for 600-V Vertical-Trench Normally-Off SiC JFETs toward 94% Efficiency Server Power Supply
Authors: Akiyama Satoru , Katoh Kaoru , Shimizu Haruka , Hatanaka Ayumu , Ogawa Takashi , Yokoyama Natsuki , Ishikawa Katsumi
Published: February 2014

A gate-drive voltage for a normally-off silicon-carbide vertical-trench junction-gate field-effect transistor (JFET) was designed for a server power supply with 94% efficiency. Since the on-state resistance of the JFET is strongly depends on the gate voltage and a large gate-leakage current between the gate electrode and source flows by applying an excessively high-gate voltage, we therefore must set an adequate turn-on gate-drive voltage to suppress the increase in power loss. The optimum gate-drive voltage design was estimated to be 2.1 V, resulting in a high efficiency of 94% even with a gate-drive voltage variation of ±0.3 V.
Evaluation of SiC Stack Cascode for 200°C Operations
Authors: Li Xue Qing , Alexandrov Peter , Hostetler John , Bhalla Anup
Published: February 2014

This paper evaluates the static and dynamic characteristics of a 1.2kV SiC stack-cascode at junction temperatures (Tj) up to 200°C. The experimental results show that, at Tj = 200°C, the SiC stack-cascode can be switched stably under a 600V-17A inductive load condition and can withstand an avalanche current of 13A for 9μs (Eav = 116mJ) for a 1.5mH load inductor. The SiC stack-cascode has no degradation in on-resistance, threshold voltage and blocking characteristics after 80 hours HTRB reliability test at 200°C ambient. These promising experimental results indicate the possibility of the SiC stack-cascode for reliable 200°C operations.
Beam Acceleration Experiment with SiC Based Power Supply and the Next Generation SiC-JFET Package
Authors: Okamura Katsuya , Osawa Yutaka , Wake Masayoshi , Yoshimoto Takashi , Sasaki Ryosuke , Takaki Koichi , Takayama Ken
Published: February 2014

Utilizing a high power discrete SiC-JFET developed by KEK, a switching power supply (SPS) that had a circuit topology of H-bridge was designed and constructed to drive the induction acceleration system for the KEK digital accelerator. Following the hopeful result with a resistive dummy load, the SPS was installed in the actual KEK Digital Accelerator system. Consequently, heavy ion beam acceleration was successfully demonstrated. Moreover, we have started to develop a next generation package for a high voltage SiC-JFET, which has the voltage rating of 2.4 kV. Two in one module construction, bonding wire free connection, and bidirectional thermal flowing are included in the design concept of the new package.
The Role of Substrate Compensation on DC Characteristics of 4H-SiC MESFET with Buffer Layer: A Combined Two-Dimensional Simulations and Analytical Study
Authors: Rao M. Hema Lata , Murty Neti.V.L. Narasimha
Published: February 2014

An analytical model of 4H-SiC metal semiconductor field effect transistor (MESFET) is proposed with buffer layer on high purity semi-insulating (HPSI) 4H-SiC substrate compensated by multiple deep level traps. The contribution of deep level traps (DLT) is projected and verified using two-dimensional simulations (Silvaco®). The modeled DC characteristics are compared with two-dimensional simulations performed on the same device as considered in the analytical model.The 4H-SiC MESFET is simulated with and without the effect of buffer layer and the electron concentration profiles in different regions are observed from two-dimensional simulations.The electron concentration profiles obtained at channel-substrate interface clearly shows that when the buffer layer is not present, the channel electrons get trapped by the deep level traps used for substrate compensation. It is also observed that the inclusion of buffer layer minimizes the extent of electron trapping by screening out the active channel from the substrate. However, the trapping phenomena take place in both the cases.We believe that the proposed model of 4H-SiC MESFET which includes the substrate compensation through multiple deep level traps may be useful for realizing SiC based monolithic circuits (MMICs) on HPSI substrates.
Monolithic Integration of Power MESFET for High Temperature SiC Integrated Circuits
Authors: Banu Viorel , Montserrat Josep , Alexandru Mihaela , Jordá Xavier , Millan José , Godignon Philippe
Published: February 2014

This work provides experimental result on fabricated 4H-SiC lateral power MESFET intended to be used in further development of high temperature integrated circuits for power application. The power SiC MESFET device was developed using a planar technology on silicon carbide and P implant isolation technique. Its destination to monolithic integration demands a lateral layout connection topology. The use of quite high doped N type epitaxial layer (1017cm-3) typical for the integrated circuits raises difficulties to keep the leakage current of the Schottky gate in a decent range. Therefore, a hexagonal close loop gate in conjunction with three metal interconnection levels was adopted, thus obtaining a compact lateral MESFET device and avoiding any drain to source parasitic leakage path. Using the tungsten gate MESFETS, the first generation of monolithic integrated lateral power MESFET device was integrated on the same wafer with digital circuits and a voltage reference analog circuit able to operate up to 250C. The temperature range can be next improved by using higher barrier for the gate contact.
3 kV Normally-Off 4H-SiC Buried Gate Static Induction Transistors (SiC-BGSITs)
Authors: Takatsuka Akio , Tanaka Yasunori , Yano Koji , Matsumoto Norio , Yatsuo Tsutomu , Arai Kazuo
Published: February 2014

3 kV normally-off SiC-buried gate static induction transistors (SiC-BGSITs) were fabricated by using an innovative fabrication process that was used by us previously to fabricate 0.7–1.2 kV SiC-BGSITs. The fabricated device shows the lowest specific on-resistance of 9.16 mΩ·cm2, compared to all other devices of the same class. The threshold voltage of this device was 1.4 V at room temperature and was maintained at values more than 1 V with normally-off characteristics at 200 °C. The device can block drain voltage of 3 kV with a leakage current density of 6.9 mA/cm2.
Real-Time Measurement of the Evolution of Growth Facets during SiC PVT Bulk Growth Using 3-D X-Ray Computed Tomography
Authors: Neubauer Georg , Salamon Michael , Uhlmann Norman , Wellmann Peter J.
Published: February 2014

In this paper, we present our new setup and technique for obtaining a real-time 3-D volume shape of the SiC crystal using X-ray computed tomography (CT). Hence, it is possible to determine in-situ the shape of the growth interface with high precision at growth temperatures above 2000 °C in a conventional 3" physical vapor transport (PVT) growth system. We show that the size and shape of a facet can be monitored at different stages during growth and furthermore the crystals face boundary can be determined with high precision throughout the whole growth process.
1700V, 5.5mOhm-cm2 4H-SiC DMOSFET with Stable 225°C Operation
Authors: Matocha Kevin , Chatty Kiran , Banerjee Sujit , Rowland Larry B.
Published: February 2014

We report a 1700V, 5.5mΩ-cm2 4H-SiC DMOSFET capable of 225°C operation. The specific on-resistance of the DMOSFET designed for 1200V applications is 8.8mΩ-cm2 at 225°C, an increase of only 60% compared to the room temperature value. The low specific on-resistance at high temperatures enables a smaller die size for high temperature operation. Under a negative gate bias temperature stress (BTS) at VGS=-15 V at 225°C for 20 minutes, the devices show a threshold voltage shift of ΔVTH=-0.25 V demonstrating one of the key device reliability requirements for high temperature operation.
Demonstration of High Quality 4H-SiC Epitaxial Growth with Extremely Low Basal Plane Dislocation Density
Authors: Tanaka Takanori , Kawabata Naoyuki , Mitani Yoichiro , Tomita Nobuyuki , Tarutani Masayoshi , Kuroiwa Takeharu , Toyoda Yoshihiko , Imaizumi Masayuki , Sumitani Hiroaki , Yamakawa Satoshi
Published: February 2014

SiC epitaxial layer with low basal plane dislocation (BPD) density of 0.2/cm2 was successfully grown under higher C/Si ratio, which is found on the investigation about growth conditions. In order to study conversion mechanism of BPDs to threading edge dislocations (TEDs), angles between directions of BPD lines on a substrate and that of moving edges of steps ([11-2) during growth were examined. Consequently, it was revealed that almost 98% of BPDs are converted to TEDs for the case of the absolute angles above 45°. This high conversion ratio is considered to be induced by enhanced lateral growth under the higher C/Si ratio condition.
40mΩ / 1700V DioMOS (Diode in SiC MOSFET) for High Power Switching Applications
Authors: Ohoka Atsushi , Horikawa Nobuyuki , Kiyosawa Tsutomu , Sorada Haruyuki , Uchida Masao , Kanzawa Yoshihiko , Sawada Kazuyuki , Ueda Tetsuzo , Fujii Eiji
Published: February 2014

Device technologies of SiC MOSFETs have nearly matured to the level of mass production and one of the remaining tasks is to serve better solutions in view of both costs and performances for practical systems. Elimination of external reverse diodes in inverter circuits is one of the solutions, by which total area of the SiC chips is greatly reduced leading to lower material cost. A DioMOS (Diode in SiC MOSFET) successfully integrates the reverse diode without any increase of the chip size from the original MOS transistor by utilizing an n-type epitaxial channel under the MOS gate for the reverse conduction path of the diode. The basic concept of the DioMOS has been proposed [1]; meanwhile, further reduction of the on-state resistance together with confirmation of high-speed switching is necessary for its application in power switching systems. In this paper, low on-state resistance (Ron) of 40mΩ and blocking voltage (BVds) of 1700V as well as improved switching performances of DioMOS are demonstrated. The measured results suggest DioMOS to be satisfactory for practical use.
SiC Epi-Channel Lateral MOSFETs
Authors: Yen Cheng Tyng , Bakowski Mietek , Hung Chien Chung , Reshanov Sergey A. , Schöner Adolf , Lee Chwan Ying , Lee Lurng Shehng , Wei Jeng Hua , Chiu Ting Yu , Huang Chih Fang
Published: February 2014

SiC lateral MOSFETs with multi-layers epi-channels were studied in this work. The epi-channel with a high concentration n-type epilayer sandwiched by two lightly doped p-type layers showed a maximum field effect mobility of 17 cm2/V.s, improved from 1.53 cm2/V.s of devices without epi-channels. These devices are normally-off with an average threshold voltage of 1.34V.
Designing of Quasi-Modulated Region in 4H-SiC Lateral RESURF MOSFETs
Authors: Nanen Yuichiro , Suda Jun , Kimoto Tsunenobu
Published: February 2014

Characteristics of high-voltage lateral silicon carbide metal-oxide-semiconductor field-effect transistors (MOSFETs) with various reduced surface field (RESURF) structures were simulated. Breakdown voltage was enhanced from 5300 V for single-zone RESURF to 7400 V for two-zone, and to 7600 V for quasi-modulated RESURF MOSFETs.
Utilization of SiC MOSFET Body Diode in Hard Switching Applications
Authors: Bolotnikov Alexander , Glaser John , Nasadoski Jeff , Losee Peter , Klopman Steven , Permuy Alfred , Stevanovic Ljubisa
Published: February 2014

This work discusses the possibility of using SiC MOSFET body diode in switching power conversion applications, focusing on performance and reliability aspects.
Development of 3.3 kV SiC-MOSFET: Suppression of Forward Voltage Degradation of the Body Diode
Authors: Yamamoto Shigehisa , Nakao Yukiyasu , Tomita Nobuyuki , Nakata Shuhei , Yamakawa Satoshi
Published: February 2014

In order to achieve cost reduction or shrinkage of power devices, an internal body diode, which forms in a MOSFET parasitically, can be designed as a free-wheeling diode in substitution for an external Schottky barrier diode (SBD). However, in a SiC p-i-n diode, forward current stress causes reliability degradation due to expansion of the electron-hole recombination-induced stacking faults. Applying the process optimization of the epitaxial layer for the reduction of recombination-induced stacking faults and the body diode screening method to 3.3 kV SiC-MOSFETs, we obtained more stable devices under forward current operation.
Investigation on Internally Unbalanced Switching Behavior for Realization of 1-cm2 SiC-MOSFET
Authors: Hino Shiro , Ito Masanao , Miura Naruhisa , Imaizumi Masayuki , Yamakawa Satoshi
Published: February 2014

The influences of internally unbalanced switching behavior on the switching characteristics and RBSOA were investigated in order to realize a large-size SiC-MOSFET. Specially designed small-size MOSFETs in which the unbalanced behavior is enhanced by adjusting the geometrical gate structures were fabricated, and their switching characteristics were evaluated. It was found that the same switching characteristics can be obtained by regarding them as MOSFETs with high inner gate resistances. A 1-cm2 SiC-MOSFET was fabricated, and high dV/dt switching and high turn-off endurance were demonstrated.
Reliability Performance of 1200 V and 1700 V 4H-SiC DMOSFETs for Next Generation Power Conversion Applications
Authors: Gajewski Donald A. , Ryu Sei Hyung , Das Mrinal , Hull Brett , Young Jonathan , Palmour John W.
Published: February 2014

We present new reliability results on the Cree, Inc., 4H-SiC, DMOSFET devices. The Cree DMOSFETs were developed to meet the demand of next-generation, high-frequency power switching applications, such as: dc-ac inversion, dc-dc conversion, and ac-dc rectification, with continually improving energy efficiency. The Cree Generation 2 DMOSFET process technology is now commercially available with 1200 V and 1700 V ratings. We have performed intrinsic reliability studies to ensure excellent wear-out performance and long field lifetime of the products. We have also performed large sample size qualification reliability acceptance tests to ensure the quality of the manufacturing and packaging processes. These comprehensive reliability studies establish new benchmarks for wide bandgap transistors and demonstrate that Crees MOSFETs meet or exceed all industrial reliability requirements. This achievement facilitates broad market adoption of this disruptive power switch technology.
Characterization of SiO2/4H-SiC Interface by Device Simulation and Temperature Dependence of On-Resistance of SiC MOSFET
Authors: Ohtsuka Kenichi , Hino Shiro , Nagae Akemi , Tanaka Rina , Kagawa Yasuhiro , Miura Naruhisa , Nakata Shuhei
Published: February 2014

MOS interface traps are characterized by device simulation on the basis of temperature dependence of lateral MOS-TEG devices on the same Al-implanted p-type region as vertical device. The simulation shows fairly large Dit in SiO2/4H-SiC interface, corresponding to the suggested trap density inside the conduction band. Temperature dependence of on-resistance is explained by application of evaluated interface properties to calculation of current voltage properties of vertical DMOSFET.
An Synergistic Dynamic 2D FEM Model of an Active Magnetic Bearing with Three Electromagnets
Authors: Pilat Adam Krzysztof
Published: February 2014

This elaboration presents a dynamic model of an Active Magnetic Bearing (AMB) developed in COMSOL Multiphysics. The electromagnetic field is calculated on the basis of Partial Differential Equations (PDEs). The calculated electromagnetic force is applied to the rotor, which is free to move. The Arbitrary Lagrangian-Eulerian (ALE) method for mesh deformation is applied to achieve rotor motion on the bearing plane. The planar rotor motion is described by a set of Ordinary Differential Equations (ODEs) solved in parallel to the electromagnetic field calculations. To enable rotor levitation, three local PD controllers are applied. The mathematical formulas of the control action are coded in the form of COMSOL equations and embedded into the rotor motion ODEs.
Analysis of a Position Control Extension on the Model of a Servo-Screw-Press
Authors: Münster Rico , Schönherr Ruben , Schlegel Holger , Drossel Welf Guntram
Published: February 2014

Currently, the achievable feedback control performance for servo-screw-presses is limited by its elastic structure. A possible approach to compensate this limitation is the extension of the velocity controller. This structural extension has the potential to improve the controller performance significantly due to a better damping of low frequencies. In this paper, the extension of the control structure by a state space feedback in the velocity control loop is examined. Considering that, the velocity control extension is investigated at a test rig which consists of a servo axis and a two mass system. Furthermore, a simulation model for the test rig is designed. The results of the simulated and experimentally obtained results of the test rig are presented and evaluated in order to make a prediction for the transferability to the simplified model of the servo-screw-press.
Influence of Anisotropy on Specific Loss Components in Grain Oriented Electrical Steel
Authors: Pluta Wojciech A.
Published: February 2014

Electrical steel sheets play an important role in magnetic circuit core design of electrical machines. Electrical steel are graded depending on value of specific total loss (PS). According to the present knowledge thePSloss consists of three components: hysteresis loss and both classical and additional eddy current loss components. Magnetic properties depend on direction of magnetization i.e. magnetocrystalline anisotropy. The determination of the specific power loss separation of electrical steel sheets in different direction to rolling direction have been performed using non-standard single sheet tester. Specific total loss was separated into hysteresis, eddy current and excess loss components. The relationship between the hysteresis and additional loss components and the magnetic anisotropy was analyzed. The aim of this paper is to provide a contribution to the better understanding of specific total loss in electrical steel with Goss texture.
Identification of Static Unbalance Wheel of Passenger Car Carried out on a Road
Authors: Prażnowski Krzysztof , Brol Sebastian , Augustynowicz Andrzej
Published: February 2014

This paper presents a method of identification of non-homogeneity or static unbalance of the structure of a car wheel based on a simple road test. In particular a method the detection of single wheel unbalance is proposed which applies an acceleration sensor fixed on windscreen. It measures accelerations cause by wheel unbalance among other parameters. The location of the sensor is convenient for handling an autonomous device used for diagnostic purposes. Unfortunately, its mounting point is located away from wheels. Moreover, the unbalance forces created by wheels spin are dumped by suspension elements as well as the chassis itself. It indicates that unbalance acceleration will be weak in comparison to other signals coming from engine vibrations, road roughness and environmental effects. Therefore, the static unbalance detection in the standard way is considered problematic and difficult. The goal of the undertaken research is to select appropriate transformations and procedures in order to determine wheel unbalance in these conditions. In this investigation regular and short time Fourier transform were used as well as wavelet transform. It was found that the use of Fourier transforms is appropriate for static condition (constant velocity) but the results proves that the wavelet transform is more suitable for diagnostic purposes because of its ability of producing clearer output even if car is in the state of acceleration or deceleration. Moreover it was proved that in the acceleration spectrum of acceleration measured on the windscreen a significant peak can be found when car runs with an unbalanced wheel. Moreover its frequency depends on wheel rotational frequency. For that reason the diagnostic of single wheel unbalance can be made by applying this method.
Mechatronic Design of an Integrated Vehicle Dynamics Control for an Energetic Optimized Battery Electric Vehicle
Authors: Buchta Robert , Liu-Henke Xiao Bo
Published: February 2014

Focus of this contribution is the constructive and functional design of an entire energetic optimized battery electric vehicle. This vehicle called M(echatronic)-Mobile was designed at the university Ostfalia using a holistic model based design approach in a continuous verification-orientated process from Model-in-the-Loop (MiL) over Software-in-the-Loop (SiL) to Hardware-in-the-Loop (HiL).
Long-Term B Cell Depletion in Murine Lupus Eliminates Autoantibody-Secreting Cells and Is Associated with Alterations in the Kidney Plasma Cell Niche
Authors: Wang Wensheng , Rangel-Moreno Javier , Owen Teresa , Barnard Jennifer , Nevarez Sarah , Ichikawa H. Travis , Anolik Jennifer H.
Published: February 2014

Autoantibodies to dsDNA, produced by autoreactive plasma cells (PCs), are a hallmark of systemic lupus erythematosus and play a key role in disease pathogenesis. Recent data suggest that autoreactive PCs accumulate not only in lymphoid tissues, but also in the inflamed kidney in lupus nephritis. We hypothesized that the variable efficacy of anti-CD20 (rituximab)–mediated B cell depletion in systemic lupus erythematosus may be related to the absence of an effect on autoreactive PCs in the kidney. In this article, we report that an enrichment of autoreactive dsDNA Ab-secreting cells (ASCs) in the kidney of lupus-prone mice (up to 40% of the ASCs) coincided with a progressive increase in splenic germinal centers and PCs, and an increase in renal expression for PC survival factors (BAFF, a proliferation-inducing ligand, and IL-6) and PC attracting chemokines (CXCL12). Short-term treatment with anti-CD20 (4 wk) neither decreased anti-dsDNA nor IgG ASCs in different anatomical locations. However, long-term treatment (12 wk) significantly reduced both IgG- and dsDNA-specific ASCs. In addition, long-term treatment substantially decreased splenic germinal center and PC generation, and unexpectedly reduced the expression for PC survival factors in the kidney. These results suggest that prolonged B cell depletion may alter the PC survival niche in the kidney, regulating the accumulation and maintenance of autoreactive PCs.
Interaction of Mesenchymal Stem Cells with Fibroblast-like Synoviocytes via Cadherin-11 Promotes Angiogenesis by Enhanced Secretion of Placental Growth Factor
Authors: Park Su-Jung , Kim Ki-Jo , Kim Wan-Uk , Cho Chul-Soo
Published: February 2014

Bone marrow–derived mesenchymal stem cells (MSC) exist in the synovium of patients with rheumatoid arthritis (RA), yet the role of MSC in RA is elusive. Placental growth factor (PlGF) expression is increased in RA synovial fluids, and blocking of PlGF attenuates progression of arthritis in mice. In this study, we observed that PlGF induced chemotaxis of MSC in a dose-dependent manner, which was blocked by anti–vascular endothelial growth factor receptor-1 peptide. MSC exposed to PlGF elicited increased phosphorylation of Akt and p38 MAPK. PlGF-mediated chemotaxis was inhibited by PI3K inhibitor (LY294002) and p38 MAPK inhibitor (SB203580), but not by ERK1/2 inhibitor (PD98059). Fibroblast-like synoviocytes (FLS) constitutively produced PlGF, but MSC released negligible amounts of PlGF. Of note, when FLS of RA patients and MSC were cocultured, PlGF production by FLS was significantly increased; such an increase was dependent on the number of added MSC. Moreover, coculture conditioned medium promoted chemotaxis of MSC and increased angiogenesis in Matrigel plugs assay, and these were suppressed by preincubation of the medium with anti-PlGF Ab. Transwell experiments revealed that MSC to FLS contact was required for the increase in PlGF production by coculture. Cadherin-11 was expressed both in FLS and MSC, and small interfering RNA knockdown of cadherin-11 in FLS significantly abrogated the enhanced PlGF production under coculture conditions. These data indicate that increased levels of PlGF in RA joints could induce the migration of MSC to the synovium, and interaction of migrated MSC with FLS via cadherin-11 may contribute to angiogenesis and chronic synovitis by enhancing the secretion of PlGF.
Perceived Outcomes of Web-Based Modules Designed to Enhance Athletic Trainers' Knowledge of Evidence-Based Practice
Authors: Welch Cailee E. , Van Lunen Bonnie L. , Hankemeier Dorice A. , Wyant Aimee L. , Mutchler Jessica M. , Pitney William A. , Hays Danica G.
Published: February 2014

Context:

The release of evidence-based practice (EBP) Web-based learning modules to the membership of the National Athletic Trainers' Association has provided athletic trainers (ATs) the opportunity to enhance their knowledge of the various EBP concepts. Whereas increasing the knowledge of EBP among ATs is important, assessing whether this newfound knowledge is being translated into clinical practice and didactic education is crucial.

Objective:

To explore the effectiveness of an educational intervention regarding EBP on the didactic instruction patterns of athletic training educators and the clinical practice behaviors of clinicians.

Design:

Qualitative study.

Setting:

Individual telephone interviews.

Patients or Other Participants:

A total of 25 ATs (12 educators, 13 clinicians; experience as an AT = 16.00 ± 9.41 years) were interviewed.

Data Collection and Analysis:

We conducted 1 individual telephone interview with each participant. After transcription, the data were analyzed and coded into common themes and categories. Triangulation of the data occurred via the use of multiple researchers and member checking to confirm the accuracy of the data.

Results:

Participants perceived the EBP Web-based modules to produce numerous outcomes regarding education and clinical practice. These outcomes included perceived knowledge gain among participants, an increase in the importance and scope of EBP, a positive effect on educators' didactic instruction patterns and on instilling value and practice of EBP among students, and an enhanced ability among clinicians to implement EBP within clinical practice. However, some clinicians reported the Web-based modules had no current effect on clinical practice.

Conclusions:

Although the EBP Web-based modules were successful at enhancing knowledge among ATs, translation of knowledge into the classroom and clinical practice remains limited. Researchers should aim to identify effective strategies to help ATs implement EBP concepts into didactic education and clinical practice.
A Mixed-Methods Study of Young Adults' Receptivity to Using Facebook for Smoking Cessation: If You Build It, Will They Come?
Authors: Ramo Danielle E. , Liu Howard , Prochaska Judith J.
Published: February 2014

Purpose.

To determine whether young adults are interested in a Facebook intervention for smoking cessation and to inform the design of such an intervention.

Design.

Mixed-methods.

Setting.

Participants throughout the United States were recruited through Facebook.

Participants.

Young adults aged 18 to 25 years who had smoked at least once in the past month.

Method.

Participants (N = 570) completed an online survey of tobacco and social media use. A subset of 30 survey completers, stratified by motivation to quit smoking, agreed to participate in a structured interview over online chat. Themes were identified by using grounded theory.

Results.

Approximately a third of the full sample (31%) reported they would want to get help to quit smoking by using Facebook. Interest in using Facebook to quit was greater among those who were more motivated to quit (χ2 = 75.2, p < .001), had made a quit attempt in the past year (χ2 = 16.0, p < .001), and had previously used the Internet for assistance with a quit attempt (χ2 = 6.2, p = .013). In qualitative interviews, social support and convenience were identified as strengths of a Facebook intervention, while privacy was the main issue of concern.

Conclusion.

Nearly one in three young adult smokers on Facebook expressed interest in using Facebook for quitting smoking. Social media approaches that respect privacy and tailor to readiness to quit are likely to maximize participation.
Interventions for Alleviating Loneliness among Older Persons: A Critical Review
Authors: Cohen-Mansfield Jiska , Perach Rotem
Published: February 2014

Objectives.

Loneliness is common among older persons and has been associated with health and mental health risks. This systematic review examines the utility of loneliness interventions among older persons.

Data Source.

Thirty-four intervention studies were used.

Study Inclusion Criteria.

The study was conducted between 1996 and 2011, included a sample of older adults, implemented an intervention affecting loneliness or identified a situation that directly affected loneliness, included in its outcome measures the effects of the intervention or situation on loneliness levels or on loneliness-related measures (e.g., social interaction), and included in its analysis pretest-posttest comparisons.

Data Extraction.

Studies were accessed using the databases PsycINFO, MEDLINE, ScienceDirect, AgeLine, PsycBOOKS, and Google Scholar for the years 1996–2011.

Data Synthesis.

Interventions were classified based on population, format, and content and were evaluated for quality of design and efficacy.

Results.

Twelve studies were effective in reducing loneliness according to the review criteria, and 15 were evaluated as potentially effective. The findings suggest that it is possible to reduce loneliness by using educational interventions focused on social networks maintenance and enhancement.

Conclusions.

Multiple approaches show promise, although flawed design often prevents proper evaluation of efficacy. The value of specific therapy techniques in reducing loneliness is highlighted and warrants a wider investigation. Studies of special populations, such as the cognitively impaired, are also needed.
Menu Labels Displaying the Kilocalorie Content or the Exercise Equivalent: Effects on Energy Ordered and Consumed in Young Adults
Authors: James Ashlei , Adams-Huet Beverley , Shah Meena
Published: February 2014

Purpose.

Determine the effect of menu labels displaying the energy content of food items or the exercise equivalent on energy ordered and consumed at lunch and energy intake for the remainder of the day in young adults.

Design.

Subjects were randomized to a menu with no labels (no-labels), menu with kilocalorie labels displaying the energy content of the food items (kcal-labels), or menu with exercise labels displaying the minutes of brisk walking needed to burn the food energy (exercise-labels).

Setting.

The study was conducted in one dining area located in a metabolic kitchen at the Texas Christian University and another located in a residence occupied by graduate students.

Subjects.

Of the 300 subjects, 55.7% were female, 77.3% were college students, 88% were white, and 88% were non-Hispanic. Mean body mass index and age were 24.2 ± 4.5 kg/m2 and 21.9 ± 2.3 years, respectively.

Intervention.

All menus contained the same food/beverage choices. Subjects ordered and consumed foods/beverages for lunch from the menu to which they were assigned. Subjects were blinded to study purpose.

Measures.

Energy ordered and consumed at lunch were assessed from the weight of the food ordered and consumed, respectively, and the energy content of the same foods available on the restaurant Web site. Postlunch energy intake was assessed by food recall.

Analysis.

Analysis of covariance, adjusted for premeal hunger levels and gender, determined the effect of menu type on energy ordered and consumed and postlunch energy intake.

Results.

Significant menu effect was observed for energy ordered (p = .008) and consumed (p = .04) at lunch. The exercise-labels group ordered significantly (p = .002) less energy (adjusted mean [confidence intervals]: 763 [703, 824] kcal) at lunch, compared to the no-labels group (902 [840, 963] kcal) but not compared to the kcal-labels group (827 [766, 888] kcal). The exercise-labels group also consumed significantly (p = .01) less energy (673 [620, 725] kcal) at lunch, compared to the no-labels group (770 (717, 823) kcal) but not compared to the kcal-labels group (722 [669, 776] kcal). Energy ordered and consumed were not different between kcal-labels and no-labels groups. There was no difference in postlunch energy intake by menu type.

Conclusion.

The menu with exercise-labels resulted in less energy ordered and consumed and this did not lead to greater energy consumption post lunch, compared to the menu with no-labels in young adults largely made up of normal-weight, non-Hispanic white college students.
Aerosols and nucleation in eastern China: first insights from the new SORPES-NJU station
Authors: Herrmann E. , Ding A. J. , Kerminen V.-M. , Petäjä T. , Yang X. Q. , Sun J. N. , Qi X. M. , Manninen H. , Hakala J. , Nieminen T. , Aalto P. P. , Kulmala M. , Fu C. B.
Published: February 2014

Abstract. Aerosols and new particle formation were studied in the western part of the Yangtze River Delta (YRD) at the Station for Observing Regional Processes of the Earth System, Nanjing University (SORPES-NJU). Air ions in the diameter range 0.8–42 nm were measured using an air ion spectrometer, and a differential mobility particle sizer (DMPS) provided particle number size distributions between 6 and 800 nm. Additionally, meteorological data, trace gas concentrations, and PM2.5 values were recorded. During the measurement period from 18 November 2011 to 31 March 2012, the mean total particle concentration was found to be 23 000 cm−3 and the mean PM2.5 value was 90 μg m−3, well above national limits. We observed 26 new particle formation events occurred during the measurement period, producing 6 nm particles at a rate of about 1 cm−3 s−1. Typical particle growth rates were between 6 and 7 nm h−1. On average, new particle formation and growth were estimated to enhance cloud condensation nuclei concentration by about a factor of two during these event days. Ion measurements showed the typical cluster band below 2 nm, with total ion concentrations between about 600 and 1000 cm−3. A peculiar feature of the ion measurements were heightened ion cluster concentrations during the nights before the event days. At 2 nm, the formation rate of charged particles was only about 0.2% of the total rate, pointing towards an only marginal role of ion-induced nucleation. Based on observations, a simple empirical criterion was deducted to estimate particle formation probability. Dominated by radiation and relative humidity, the criterion can predict the occurrence of particle formation with a 90% accuracy. In a similar fashion, a reasonably accurate estimate of particle formation rates was derived. Combined, these parameters allow for a description of particle formation based on a few basic measured variables.