bluuebunny/crossref_metadata_2025 huggingface dataset:
Dual MOSFET Hydrogen Sensors with Thermal Island Structure
Authors: Kim Bum Joon , Kim Jung Sik
Published: March 2013

A low powered hydrogen gas sensor of the FET (field-effect transistor) structure was designed, fabricated and characterized for self-compensation to outer environments. The dual-gate FET hydrogen sensor was integrated with a micro-heater and two Pt-gate FETs; a sensing device for hydrogen detection, and a reference device as an electrical compensator. The identical output between the sensitive-FET and reference-FET was stable at temperatures ranging from room temperature to 250°C due to the same temperature dependence of the currentvoltage (IV) characteristics. The Pt-FET sensor showed stable responses to hydrogen at a range of operation temperatures. The optimal point in the micro-heater operation for 5,000 ppm H2 gas injection was approximately 150°C. The highest sensitivity was 0.112 mA, and the response and recovery times were 18 sec and 19 sec, respectively. The low-power MOSFET gas sensor was found to be suitable for applications in portable gas monitoring units and automobiles.
Selective Optical Gas Sensors Using Butterfly Wing Scales Nanostructures
Authors: Kertész Krisztián , Piszter Gábor , Jakab Emma , Bálint Zsolt , Vértesy Zofia , Biró László Péter
Published: March 2013

Photonic crystals are periodic dielectric nanocomposites, which have photonic band gaps that forbid the propagation of light within certain frequency ranges. This property enables one to manipulate light with amazing facility. Such nanoarchitectures frequently occur in living organism like butterflies and beetles. Butterfly scales are particularly well suited to be used as optical gas sensors as their nanoarchitecture is an open sponge-like type, composed of chitin and air. The open nanoarchitecure allows fast gas exchange. The spectral change of the reflected light depends on the composition of the ambient atmosphere and also on the wing nanostructure. In this work we show the results of recent measurements on nine Polyommatine species with dorsal blue coloration. Their color is generated by similar pepper-pot type nanoarchitectures which exhibit species specific characteristics, associated with species specific color. Experiments were carried out changing the concentration and nature of test vapors while monitoring the spectral variations in time. Proper data processing results gas-selective and concentration dependent signals. Our work shows a way to a prospective integrated biological - optical sensor combining light-weight and low power consuming with environmental friendly production.
Grain Boundary Phase Analysis for Y2O3-Doped AlN Ceramics
Authors: Mao Fang Fang , Wang Xian Hao , Zheng Qiang , Zhang Fa Qiang , Zhang Zhao Quan , Gu Hui
Published: March 2013

Y2O3 is a common sintering additive of AlN ceramics to achieve densification and remove the oxygen impurity, resulting in a typically grain boundary phase (GBP) Y3Al5O12 (YAG). Two AlN ceramics with 3wt% and 5wt% Y2O3 intended for thermal conductivity study were sintered at 1800 °C for 4h. X-ray diffraction (XRD) indicates that GBP could either be YAG or YAP (YAlO3) phase, while the selected area electron diffraction (SAED) and energy dispersive X-ray (EDX) in TEM identifies it as YAP instead of YAG. The electron back-scattering diffraction (EBSD) in SEM further confirms the general presence of YAP phase in both samples. In meanwhile, two types of Al-rich GBPs were also detected by TEM, which could account for extra dopant in the microstructure. GBP contents in the both samples were quantified by K-value method (XRD) and from backscattered electron images. Such analyses of GBPs are helpful to understand the sintering mechanism and evaluate their contribution to the thermal conductivity of AlN.
Joining of C/SiC Composite and TC4 Alloy Using 70Ag28Cu2Ti Active Brazing Alloy
Authors: Li Jia Ke , Liu Xiu , Zhou Jian Er
Published: March 2013

C/SiC composite and TC4 alloy were successfully brazed using 70Ag28Cu2Ti (wt. %) as filler metal at 820 °C~920 °C for 5 min ~30 min. The effects of brazing parameters on the microstructures, phase composition, shear strength of the brazed joints were investigated by SEM, XRD. The mechanical performances of the brazed joints were measured by a universal mechanical testing machine. The results show that successful joining of C/SiC composite and TC4 alloy owes to interfacial reactions between the brazing alloy and the parent materials, and resultantly produce TiC, Ti5Si3 and Ti-Cu serial compounds at the interfaces; the interfacial structure of the brazed joint is C/SiC composite / TiC / Ti5Si3 /Ag (s.s) +Cu (s.s) / TiCu2 / Ti3Cu4 / TiCu / Ti2Cu / TC4 from C/SiC composite side to TC4 alloy side; the maximum shear strength of the brazed joint is 53.3 MPa at 860°C for 10min.
Influencing Factors of Macrosporous Ordering in TiO2 and ZrO2 Inverse Opals
Authors: Zhang Hui , Xu Xiao Long , Li Fan , Jin Bin Bin , Zhao Su Ling
Published: March 2013

TiO2 inverse opals, as well as used as photonic crystals, can be applied to the dye sensitized solar cells (DSSC), photocatalysis, and so on. In above applications, ordering of pore arrangement in TiO2 inverse opal is crucial as it determines the application effect of TiO2 inverse opal. In this paper, TiO2 inverse opals were prepared by infiltrating and removing of polystyrene (PS) colloidal crystal templates. Using scanning electron microscope (SEM), it is found that the pore structure of inverse opals can be tuned by using different heating temperature and different size of PS spheres, and ordering of pore arrangement is strongly affected by ordering of PS spheres alignment, heating temperature, and size of PS spheres.
Doping Effect of Alkali Ions on the Microstructural and Electrical Properties of ZnO-Pr6O11-Based Varistor Ceramics
Authors: Peng Zhi Jian , Jiang Feng , Feng Hai , Fu Xiu Li
Published: March 2013

The microstructural and electrical properties of ZnO-Pr6O11-based ceramics fabricated with 97.5mol% ZnO + 0.5mol% Pr6O11 + 1.0mol% Co3O4 + 0.5mol% Cr2O3 + 0.5mol% MNO3 (M=Li, Na, K, or Rb) were investigated. Scanning electron microscopy analysis revealed that the doping of alkali ions would inhibit the growth of ZnO grains in the as-prepared ZnO-Pr6O11-based ceramics, in which the addition of K+ ion showed the strongest effect. Through the analysis of electric field vs current density characteristics, it was found that the doping of Li+ ion into ZnO-Pr6O11-based ceramics would change the varistor into ohmic resistor, but the addition of Na+, K+ or Rb+ ion could improve the nonlinearity of the varistors, in which the addition of K+ ion resulted in the strongest improving effect.
A Review of the Influential Factors on the Ferroelectric Domain Structure in BiFeO3 Thin Films
Authors: Huang Yao Ting , Fu Xiu Li , Zhao Xiao Hong , Tang Wei Hua
Published: March 2013

BiFeO3 is a very promising multiferroic materials, which can present ferroelectric and antiferromagnetic properties at room temperature (Tn=643 K, Tc= 1103 K). Ferroelectric domains in BiFeO3 thin films have attracted much attention due to their potential applications in memory devices. The aim of this paper is to review the main factors which can influence the ferroelectric domain structure in BiFeO3 thin films, including substrate, doping and film thickness.
Effect of Ar Pressure on Properties of Polycrystalline CdZnTe Films
Authors: Yao Bei Ling , Huang Jian , Cai Liang Min , Tang Ke , Ren Bing , Zhou Jie , Le Jun , Shen Li Ya , Zhu Yue , Wang Lin Jun
Published: March 2013

Polycrystalline CdZnTe (CZT) films were grown by close-spaced sublimation method. The CdZnTe films were prepared on fluorine doped tin oxide (FTO) glass substrates at various argon (Ar) pressures from 200 Pa to 700 Pa. A comparative study of the films at different pressures was obtained by X-ray diffraction (XRD), scanning electron microscope (SEM) and Energy dispersive spectrometer (EDS) respectively. The XRD studies revealed that CdZnTe films had a preferential orientation along the (111) phase except the one at 500 pa. EDS analysis indicated that the increasing of Ar pressure decreased Zn content.
Theoretical and Experimental Studies on Strength and Stiffness of Vacuum Glazing
Authors: Liu Xiao Gen , Bao Yi Wang
Published: March 2013

In order to understand the carrying capacity and deformation characteristics of vacuum glazing, experimental and theoretical research were carried out on load bearing capacity of four sides supported vacuum glazing, the load-displacement and load-stress curves of the test samples under uniform load were obtained. The experimental result indicated that under the test samples have the same thickness, the capacity of resisting wind load of the vacuum glazing is not so strong as common glass plate. To design methods of the vacuum glazing plate, one of those is to calculate the stresses and the deflection with the equivalent thickness as an integral model. The equivalent thickness coefficient of the vacuum glazing is about 0.85~0.9, and the magnitudes of the equivalent thickness coefficient of the vacuum glazing is decreases with increasing of the glass thickness, but not been influenced by the length and width dimensions of the glass plate. Take into account the influence of long term tensile stresses in vacuum glazing due to atmospheric pressure on the glass strength, the calculation formula of resistance to wind load for the vacuum glazing was given.
Fabrication and Oxidation-Resistance Property of Coated ZrB2-YAG-Al2O3 Multi-Phase Ceramics
Authors: Song Jie Guang , Wang Fang , Xu Ming Han , Li Shi Bin , Ji Gang Chang
Published: March 2013

Zirconium diboride is widely applied because of some excellent performances. The results show the A1(OH)3-Y(OH)3/ZrB2 composite powders is prepared by a co-precipitation method, the shell-core structure A12O3-Y2O3/ZrB2 composite powders is prepared by sintering A1(OH)3-Y(OH)3/ZrB2 composite powders. The coating and density ZrB2-YAG-Al2O3 multi-phase ceramics is sintered at 1700°C, 20MPa for 4min by using Al2O3-Y2O3-80wt%ZrB2 composite powders, the oxidation weight is increased with increasing the oxidation temperature, however, the oxidation weight is decreased with increasing the YAG-Al2O3 content. ZrB2 reacted with O2 to form B2O3, and B2O3 is reacted with Al2O3 to form Al18B4O33, which is melted and coated on the surface of ceramics to form a protective layer for the oxidation resistance of ceramics at high temperature.
Preparation of High Performance SiCf/SiC Composites through PIP Process
Authors: Chen Ming Wei , Qiu Hai Peng , Jiao Jian , Li Xiu Qian , Wang Yu , Zou Hao
Published: March 2013

SiC fiber reinforced SiC matrix (SiCf-SiC) composites with and without pyrolytic carbon interphase were prepared by polymer impregnation pyrolysis (PIP) progress. The effect of pyrolytic carbon interphase on the fracture behavior and mechanical properties of SiCf/SiC composites was studied. The results show that pyrolytic carbon interphase weakened the bonding between the matrix and the fibers. The mechanical properties of SiCf-SiC composites with carbon coating were improved effectively via fiber debonding and pulling-out from matrix under external loads. The flexural strength and fracture toughness of the above composites reached up to 498.52MPa and 24.09MPa•m1/2, respectively.
Testing and Evaluation of Mechanical Properties for Anisotropic Engineering Materials with Varied Loads
Authors: Zhu Huai Liang , Yu Li Feng , Ni Jing , Wang Xue , Luo Ren An
Published: March 2013

This paper is aimed at investigating the influence of load-bearing style on the mechanical behavior of anisotropic engineering materials. The study on elastic constants and failure forms of materials will be presented under different loading condition. Firstly, the mechanical properties of unidirectional holey laminated materials are discussed based on the uniaxial tensile tests. The equivalent elastic modulus, Poisson’s ratio and shear modulus are obtained, and the pattern and mechanism of failure are analyzed. Then, the biaxial tensile tests are carried out for PVC orthotropic membrane materials with different stress ratio between the warp and weft direction. A comparison of limit strengths under biaxial loadings is given with that in uniaxial loading case. Finally, the dynamical behaviors of shape memory alloy (SMA), iron wire, and rubber composite as well as compound rubber are studied respectively by impact-tension tests. The failure forms, energy dissipation ratio and impact-tension toughness of materials are analyzed. It is shown that the mechanical properties and failure pattern of anisotropic materials have much to do with the load-bearing styles. It agrees well with actual properties of anisotropic material used in engineering structures.
Effect of Cerium Oxide on Sinterability, Microstructure and Properties of Anorthite-Based Glass/Ceramic Composites
Authors: Dong Wei Xia , Bao Qi Fu , Gu Xing Yong , Huang Yan Chun
Published: March 2013

The properties of anorthite-based glass/ceramic with different amounts of CeO2 addition had been investigated in this paper. The glass/ceramics with small amounts of CeO2 addition could be well sintered at 850~900°C. The water absorption was examined to evaluate the sintering behavior of the samples. The crystalline phase,microstructure, dielectric properties, thermal expansion and bending strength were characterized by X-Ray diffraction (XRD), scanning transmission electron microscope (SEM), impedance materials analyzer, thermal expansion analyzer and flexural strength analyzer. The results showed the 1wt % CeO2-doped glass/ceramics sintered at 900 °C have optimum properties of ε = 6.282, tanθ = 2.18×10-3 at 1 MHz and a thermal expansion coefficient of 3.32×10-6 °C-1 (25~500 oC) matched with silicon chip (3.4×10-6 °C -1). Obviously, CeO2 could be used as a suitable sintering aid that improves densification of the glass/ceramic composites.
Preparation and Characterization of Nb2O5-Al2O3 System Ceramics with Different Al2O3 Additions
Authors: Zhang Xiao Zhen , Zhou Jian Er , Jiang Yu Hua , Wu Chun Rong , Lin Chuan Ying
Published: March 2013

The Nb2O5-Al2O3 binary system ceramics were prepared by high temperature solid state reaction sintering, using Nb2O5 and Al2O3 micro powder as the raw materials. The samples were characterized by XRD, SEM, thermodilatometric analysis and mechanical strength measurement. The influences of Al2O3 content on the phase composition, microstructure, thermal expansion properties and bending strength were investigated. Results show the samples shows obvious changes in phase composition and microstructure with the addition of Al2O3 from 2.5% to 15%. The pure Nb2O5 ceramic is composed of monoclinic phase Nb2O5, while different monoclinic aluminum niobates were formed with different Al2O3 additions. Obvious microcracking can be observed for the samples without and with 2.5% and 7.5% Al2O3 additions. The addition of Al2O3 leads to significant increase of bending strength, and all the samples keep relatively low thermal expansion coefficient (TEC). The Nb2O5-Al2O3 binary system ceramics with ultra low TEC (0.55~0.86×10-6°C-1) and improved bending strength (50.4~70.6MPa) could be obtained with the addition of 7.5~15% Al2O3 when sintered at 1390°C for 2h.
A Review on Fabrication Methods of BiFeO3 Thin Films
Authors: Huang Yao Ting , Fu Xiu Li , Zhao Xiao Hong , Tang Wei Hua
Published: March 2013

BiFeO3is a very promising multiferroic materials, which can present ferroelectric and antiferromagnetic properties at room temperature (Tn=643 K, Tc= 1103 K). Because the fabrication methods of BiFeO3films play a significant role on their properties, various processing techniques have been developed in recent years for the preparation of such films. In this paper, the main fabrication processes on BiFeO3thin films were reviewed, including two important chemical processes, chemical solution deposition and metal-organic chemical vapor deposition, and two commonly applied physical processes, pulsed laser deposition and radio-frequency magnetron sputtering.
Syntheses and Characterizations of Supercapacitors Using Nano-Sized ZnO/Nanoporous Carbon Electrodes and PVA-Based Polymer-Hydrogel Electrolytes
Authors: Rosi Memoria , Iskandar Ferry , Mikrajuddin Abdullah , Khairurrijal Khairurrijal
Published: March 2013

Supercapacitors have been successfully fabricated using nano-sized ZnO/nanoporous carbon (nano-sized ZnO/NPC) electrodes and various hydrogel electrolytes. The nano-sized ZnO/NPC materials have been prepared from zinc acetate (Zn(CH3COO)2) and coconut shell using a simple heating method. Polyvinyl alcohol (PVA) hydrogel blended with phosphoric acid (H3PO4), lithium hydroxide (LiOH) and sodium sulfate (Na2SO4) electrolytes, respectively, has been located between the electrodes. Two of the nano-sized ZnO/NPC electrodes with area of 1 cm2 and those PVA hydrogel electrolytes were pressed together and annealed at 60 °C for 60 min. to construct the supercapacitors. It has been found that the supercapacitor with nano-sized ZnO/NPC electrodes and Na2SO4 electrolyte has the highest capacitance of 60.4 Fg-1.
Development of Phase Field Simulation for the Growth of Dendrite Structure of Al-Si Cast Alloy
Authors: Ramdan Raden Dadan , Takaki Tomohiro , Djuansjah Joy Rizki Pangestu , Sofyan Bondan Tiara , Hamzah Esah
Published: March 2013

Micro to nano scale study of dendrite structure is important in order to have better properties control of casting product. The present study concerns on the morphological study of dendrite structure by phase-field simulation, in order to obtain the morphological growth of this structure that close its real morphology. Focus was given on the morphological growth of dendrite structure of Al-Si cast alloys, therefore thermodynamic data were taken for this type of materials. Anisotropy noise, strength of anisotropy and different undercooled conditions were applied as the variable parameters in the present works. It was observed that by introducing higher anisotropy noise, higher degree fragmentation of dendrite structure was obtained. Similar condition was obtained by introducing higher strength of anisotropy value, that higher degree of fragmentation was obtained. Both of these phenomena was also supported by the heat flux rate features of these variations that higher heat flux rate to almost all direction was obtained with the higher value of anisotropy noise and strength of anisotropy. In addition it was also observed that higher degree fragmentation of dendrite only possible to occur if sufficient undercooled condition established.
Effect of Cold Rolling Treatment on the Formation of Titanium Oxide Layer on Ti6Al4V Alloys by Thermal-Electrochemical Anodizing Processes
Authors: Ramdan Raden Dadan , Djuansjah Joy Rizki Pangestu , Suratman Rochim , Hamzah Esah , Izman Sudin
Published: March 2013

The present work concerns on preparing suitable titanium alloy substrate that might induce better characteristic of titanium oxide layer on the substrate. Different degree of cold rolling treatments were applied on Ti6Al4V alloy before thermal-electrochemical anodizing processes. The later processes were performed to produce titanium oxide layer which combines thermal process by heat treatment and followed with electrochemical anodizing process. After thermal heat treatment process, it was observed more homogeneous titanium oxide layer for the samples given cold rolling treatment as compared with sample without the treatment. This condition is believed due to the finer substrate surface after cold rolling treatment as observed from surface roughness measurement. Similar situation was observed after anodizing process that irregular oxidized layer was observed for sample without cold rolling treatment, whereas more homogenous layer was observed for sample with cold rolling treatment. Except for sample without cold rolling treatment, anodizing treatment tends to create finer oxidized layer. Therefore, it can be concluded that cold rolling treatment on titanium substrate before oxidizing process induces the formation of homogeneous oxide layer, whereas additional anodizing process create finer titanium oxide layer.
Ethylene Glycol Route Synthesis of Nickel Oxide Nanoparticles as a Catalyst in Aquathermolysis
Authors: Noorlaily Prawistin , Nugraha Mohamad Insan , Khairurrijal Khairurrijal , Abdullah Mikrajuddin , Iskandar Ferry
Published: March 2013

NiO nanoparticles have been synthesized as catalyst in aquathermolysis for viscosity reduction of heavy oil. NiO nanoparticles were prepared by using NiCl2•6H2O as raw material via ethylene glycol route. In the process, NH4HCO3 and ethylene glycol were used as reductant and to prevent nanoparticles from agglomeration, respectively. The obtained NiO nanoparticles have crystallite size about 15.4 nm, nearly uniform particles size, well dispersion with diameter around 65 nm, spherical morphology, and the spesific surface area 158.4 m2/gram. In a catalytic activity test, it showed that the viscosity of heavy oil could be reduced up to 22% when NiO nanoparticles were added in aquathermolysis reaction. This result confirmed that NiO nanoparticles have good catalytic properties in the viscosity reduction of heavy oil.
Bipolar Conduction across a Wafer Bonded p-n Si/SiC Heterojunction
Authors: Gammon Peter Michael , Pérez-Tomás Amador , Jennings Michael R. , Sanchez Ana M. , Fisher Craig A. , Thomas Stephen M. , Donnellan Benedict T. , Mawby Philip  Andrew
Published: March 2013

This paper describes the physical and electrical properties of a p-n Si/on-axis SiC vertical heterojunction rectifier. A thin 400nm p-type silicon layer was wafer-bonded to a commercial on-axis SiC substrate by room temperature hydrophilic wafer bonding. Transmission electron microscopy was used to identify the crystallographic orientation as (0001)SiC//(001)Si and to reveal an amorphous interfacial layer. Electrical tests performed on the p-n heterodiodes revealed that, after an additional 1000oC anneal, the rectifier exhibit remarkably low leakage current (10nA/cm2 at an anode voltage of V=-6V), improved on-resistance due to bipolar injection and a turn-on voltage close to the p-n heterojunction theoretical value of 2.4V.
Selective 4H-SiC UV Detectors
Authors: Kalinina Evgenia V. , Konstantinov O. , Lebedev A.A. , Gol’dberg Yu.
Published: March 2013

Carcinogenic (bactericidal) radiation (λ = 200–300 nm with a peak at 254 nm) is present in natural (Sun) and artificial (lamps) source of UV radiation. Its intensity is very low as compared to other types of radiation, but it strongly affects the health of human beings. To prevent oncological diseases, it is important to monitor the carcinogenic radiation level; i.e., selective photodetectors are required. A UV photodetectors based on n-4H-SiC Schottly barriers and p+-n junctions are proposed. The quantum efficiency spectrum of such detectors is very close to the spectrum of relative action of carcinogenic radiation on human beings due to the direct optical transition at 4.9 eV in 4H-SiC. The quantum efficiency (at the spectral peak 254 nm) amounts to about 0.3 electrons/photon for virtually zero sensitivity in other spectral regions. Quantum efficiency in the wavelength range 247–254 nm is practically independent of temperature in the range from −100 to +300°C.
Fabrication of Broadband Antireflective Sub-Wavelength Structures on Fluorescent SiC
Authors: Ou Yi Yu , Jokubavicius Valdas , Kaiser Michl , Wellmann Peter J. , Linnarsson Margareta K. , Yakimova Rositza , Syväjärvi Mikael , Ou Hai Yan
Published: March 2013

Surface nanocones on 6H-SiC have been developed and demonstrated as an effective method of enhancing the light extraction efficiency from fluorescent SiC layers. The surface reflectance, measured from the opposite direction of light emission, over a broad bandwidth range is significantly suppressed from 20.5% to 1.0 % after introducing the sub-wavelength structures. An omnidirectional light harvesting enhancement (>91%), is also achieved which promotes fluorescent SiC as a good candidate of wavelength converter for white light-emitting diodes.
Investigation of Die Attach for SiC Power Device for 300°C Applications
Authors: Drevin-Bazin A. , Badawi F. , Lacroix F. , Barbot J.F.
Published: March 2013

The mechanical properties of die attach system SiC/Au-Ge/Au-Ni-Cu-Si3N4 using the eutectic Au-Ge solder (Teut = 356°C) were investigated in a temperature range up to 300°C. The as-resulting structure of the solder is observed to be lamellar with pockets of high concentration of Au close to the interfaces. The shear strength of joint decreases with temperature but, even at 300°C, its value is well higher than the IEC standard. The creep behavior of Au-Ge solder alloy was also investigated at 300°C for different strain levels. The creep curves show a high creep resistance even for high stress level.
4H-SiC Digital Logic Circuitry Based on P+ Implanted Isolation Walls MESFET Technology
Authors: Alexandru Mihaela , Banu Viorel , Godignon Philippe , Vellvehi Miguel , Millan José
Published: March 2013

The design and development of SiC integrated circuits (ICs) nowadays is a necessity due to the increasing demand for high temperature intelligent power applications and intelligent sensors. Due to the superior electrical, mechanical and chemical proprieties of 4H-SiC poly-type, 4H-SiC MESFET transistor is a good compromise for ICs on SiC able to work at higher temperatures (HT) than on Si. This paper presents new experimental results of approaching embedded logic gates with SiC MESFETs and resistors, built in junction-isolated tubs. The P+ implantation isolation technology offers important perspectives regarding the integration density of devices per unit area and wafer surface, being able to use far more complex design geometry for modeling ICs on SiC.
PWM Power Supply Using SiC RESURF JFETs with High Speed Switching
Authors: Hatsukawa Satoshi , Tsuno Takashi , Fujikawa Kazuhiro , Shiga Nobuo , Wuren Tuya , Wada Kazuyuki , Ohira Takashi
Published: March 2013

400V/2.5A 4H-SiC JFETs, having a reduced surface field (RESURF) structure have been fabricated. Measurements on the on-resistance, blocking, and switching characteristics were carried out. It was confirmed that the JFET has fast switching characteristics. A demonstration of a Pulse Width Modulation (PWM) decoder using JFETs was carried out. The input waveform, which is pulse width modulated 20.5MHz at 4.1MHz sine wave, as able to be decoded at 4.1MHz sine wave.
Silicon Carbide Multilevel Converters for Grid-Connected PV Applications
Authors: Mostaghimi Omid , Wright Nicholas G. , Horsfall Alton B.
Published: March 2013

To fulfill the space and weight requirements of the photovoltaic systems, an all-SiC transformer less dc-dc multilevel converter based on the Cockcroft-Walton voltage multiplier capable of providing high voltage conversion ratios without an extremely high duty cycle has been realised. The evaluation of converter performance utilising SiC devices have been detailed and presented. The converter offers self-balancing which maintains the same output at all output levels, reducing the complexity of the control strategy. SiC Schottky diodes were used to achive lowest reverse recovery and fast switching while evaluating the high voltage and high frequency performance of the SiC MOSFET in the multilevel boost converter.
40 kW/L High Switching Frequency Three-Phase AC 400 V All-SiC Inverter
Authors: Sasaki Kensuke , Sato Shinji , Matsui Kohei , Murakami Yoshinori , Tanimoto Satoshi , Tanisawa Hidekazu
Published: March 2013

We, the R&D Partnership for Future Power Electronics Technology (FUPET), have reported a forced-air-cooled DC 600 V three-phase AC 400 V inverter built with SiC-JFETs and SiC-SBDs and designed to attain an output power density (OPD) of 40 kW/L with a switching frequency (fSW) of 50 kHz. This paper reports the test results of this inverter attaining an OPD of 40 kW/L in operating a 3-phase motor with fSW = 50 kHz, and an OPD of more than 60 kW/L in operating an equivalent circuit with fSW = 20 kHz by adopting specialized high speed drive circuit boards.
On the Assessment of Temperature Dependence of 10 - 20 kV 4H-SiC IGBTs Using TCAD
Authors: Nawaz Muhammad , Chimento Filippo
Published: March 2013

This paper addresses and evaluates the temperature dependence performance of silicon carbide (4H-SiC) based insulated gate bipolar transistors (IGBTs) using two dimensional numerical computer aided design tool (i.e., Atlas TCAD from Silvaco). Using identical set of device physical parameters (doping, thicknesses), simulated structure was first caliberated with the experimental data. A minority carrier life time in the drift layer of 1.0 – 1.6 µs and contact resistivity of 0.5 - 1.0 x 10-4 Ω-cm2 produces a close match with the experimental device. A set of n type IGBT structures were then numerically simulated to extract the conduction losses for various blocking voltage classes. An on-resistance first decays with temperature (i.e., increased in ionization level, and increase in minority carrier life time), stays nearly constant with further increase in the temperature (may be all carriers are now fully ionized and increase in carrier life time is compensated with decrease in the carrier mobility) and finally increases linearly with temperature (>450 oC) due to decrease in the carrier mobility. Compared with Si based IGBTs, numerical simulation predicts lower VCEON and RON values for 4H-SiC based IGBTs for higher voltage classes and hence potential for achieving smaller conduction losses for SiC based IGBTs.
An Experimental Study on Compact Equivalent Circuit Modeling of SiC Schottky Barrier Didoes
Authors: Hirano Makiko , Funaki Tsuyoshi
Published: March 2013

Circuit simulation is of assistance to design and evaluate a power conversion circuit. A compact and accurate power device model is indispensable for obtaining appropriate circuit simulation results. This paper studies the compact equivalent circuit modeling of SiC Schottky Barrier diode (SiCSBD) and evaluates the developed model in turn-off switching operation. Two SiCSBDs having different specification are modeled and evaluated in this paper. The results show that the switching characteristics of SiCSBDs can be modeled with the equivalent circuit, whose configurations and parameters are identified from static I-V and C-V characteristics.
The Impact of the Surface Treatments on the Properties of Gan/3C-SiC/Si Based Schottky Barrier Diodes
Authors: Han Ji Sheng , Tanner Philip , Dimitrijev Sima , Shuang Qu , Shen Yan , Xu Xian Gang
Published: March 2013

In this work, we studied the effect of surface preparation and substrate temperature during sputter deposition of Schottky contacts on N-GaN/SiC/Si substrates, looking at parameters such as on-resistance, reverse leakage, and contact barrier height. Ti, Ni and Mo were sputtered to form the contacts, and we characterized the I-V curves with the different substrate temperatures during the sputtering as shown in Figure 1. For the Ti Schottky contact, the substrate temperature of 100oC during the sputtering demonstrates the minimum series resistance with Rs about 0.04cm2, while temperatures greater than 3000C increased reverse bias leakage. The Mott-Schottky plot reveals a barrier height of 1.2V for this contact. Results for sputtered Ni contacts using different substrate temperatures will also be presented, as well as the effect of Ar sputter cleaning before contact deposition.
SiC/Si Pseudosubstrates for AlGaN Nanoelectronic Devices
Authors: Hiller Lars , Tonisch Katja , Pezoldt Joerg
Published: March 2013

Heteroepitaxial AlGaN/GaN on SiC/Si pseudosubstrate was used to fabricate three-terminal junction devices. Narrow bar and wide bar type active regions were fabricated. The measurement at room temperature showed predicted nonlinear behavior (previously reported about as negative type rectification). Unusual, positive type rectification for two dimensional electron gases was also observed. The electrical characteristics depend on the geometrical configuration of the devices.
Graphene-on-Porous-Silicon Carbide Structures
Authors: Mynbaeva Marina G. , Sitnikova Alla A. , Lebedev Sergey P. , Petrov Vassili N. , Kirilenko Demid A. , Kotousova Irina S. , Smirnov Alexander , Lavrent'ev Alexander A.
Published: March 2013

3D–SiC/graphene structures were fabricated on the basis of SiC wafers by first producing micro–porous material by anodization, and then using two–step annealing to modify the porous matrix and cover it with a 2D carbon coating. Topological features of the obtained structures extend from macro– down to nano–scale. It is expected that such topology in combination with high resistance to corrosion, and bio–compatibility of both SiC and nano–carbon will make the 3D–SiC/graphene structures prospective for tissue–inducing matrixes.
Low-Temperature Transport Properties of Graphene and Multilayer Graphene on 6H-SiC
Authors: Lebedev Alexander A. , Agrinskaya Nina V. , Berezovets Viacheslav A. , Kozub Veniamin I. , Lebedev Sergey P. , Sitnikova Alla A. , Kirilenko Demid A.
Published: March 2013

Transport properties of multigraphene layers on 6H-SiC substrates was studied. It was found that the curves of magnetoresistance and Shubnikov- de Haas oscillations shown the features, typical for single-layred graphene. The low temperature resistance demonstrated an increase with temperature increase, which also corresponds to a behavior typical for single-layered graphene (antilocalization). However at higher temperatures the resistance decreased with an increase of temperature, which corresponds to a weak localization. We believe that the observed behavior can be explained by a parallel combination of contributions to the conductivity of single-layered graphene and of multigraphene.
Energy Gaps Induced by a Semiconducting Substrate in the Epitaxial Graphene Density of States
Authors: Davydov Sergey Yu. , Lebedev Alexander A. , Lebedev Sergey P.
Published: March 2013

The simple model for the one-layer graphene energy gaps induced by the substrate energy gap is pro-posed.
Fast Growth Rate Epitaxy by Chloride Precursors
Authors: La Via Francesco , Camarda Massimo , Canino Andrea , Severino Andrea , La Magna Antonino , Mauceri Marco , Vecchio Carmelo , Crippa Danilo
Published: March 2013

In this paper the epitaxial process with chloride precursors has been described. In particular it has been shown that the growth rate can be increased to about 100 μm/h but higher growth rate can be difficult to reach due to the limited surface diffusion at the usual temperature of SiC epitaxy. This process gives several advantages because it gives the opportunity to increase the throughput and consequently to reduce the cost of epitaxy, using new reactor structures, and to reduce several kind of defects (Basal Plane Dislocations, Stacking Faults, Threading Dislocations) and to decrease the surface roughness at the same time.
Reduction of Threading Screw Dislocation Utilizing Defect Conversion during Solution Growth of 4H-SiC
Authors: Harada Shunta , Yamamoto Yuji , Seki Kazuaki , Ujihara Toru
Published: March 2013

Reduction of threading screw dislocation without polytype transformation from 4H-SiC was performed by the combination of step-flow growth and spiral growth. On a vicinal 4H-SiC seed crystal, threading screw dislocations are converted to Frank-type stacking faults by step-flow during solution growth. As the growth proceeds, the defects are excluded to the crystal. Thus utilizing the conversion, high quality SiC crystal growth without threading screw dislocations is expected to achieve. However, at the same time, polytype transformation is caused by the occurrence of 2D nucleation. By using the special shape of seed crystal, we successfully grew high quality 4H-SiC crystal without threading screw dislocation and polytype transformation.
The Growth of 3-Inch 4H-SiC Si-Face Epitaxial Wafer with Vicinal Off-Angle
Authors: Masumoto Keiko , Kojima Kazutoshi , Okumura Hajime
Published: March 2013

We grew epitaxial layers on 3-inch epitaxial wafers with a vicinal off-angle, using a horizontal hot-wall chemical vapor deposition system that had a reactor capacity of 3 x 150 mm. Uniformity (σ/mean) of thickness and carrier concentration as small as 1.7% and 5.6%, respectively, were successfully obtained. We succeeded in decreasing triangular surface defects and polytype inclusions by increasing the growth temperature and lowering the C/Si ratio. In addition, I-V characteristics of Schottky barrier diodes on an epitaxial layer showed that a high blocking voltage of 960 V and a low leakage current of less than 1 x 10-6 A/cm2 were obtained with a yield of 78%.
Step-Bunching Free and 30 μm-Thick SiC Epitaxial Layer Growth on 150 mm SiC Substrate
Authors: Miyasaka Akira , Norimatsu Jun , Fukada Keisuke , Tajima Yutaka , Muto Daisuke , Kimura Yusuke , Odawara Michiya , Okano Taichi , Momose Kenji , Osawa Yuji , Osawa Hiroshi , Sato Takayuki
Published: March 2013

The production of 150 mm-diameter SiC epi-wafers is the key to the spread of SiC power devices. Besides, step-bunching free surface leads to high-performance devices. We have developed the production technology of the epitaxial growth with smooth surface morphology for 4º off Si-face 4H-SiC epitaxial layers on 150 mm diameter substrates. The various area observations of the surface by optical surface analyzer, confocal microscope and atomic force microscope revealed that there was no conventional step-bunching in whole wafer surface. While creating step-bunching free surface is more difficult for thicker epilayer growth, we have achieved step-bunching free surface for 30-μm thick epilayer on a 150 mm diameter substrate. The typical values of thickness uniformity of the 30μm-thick epilayer are 0.5% (σ/mean) and 1.7% (range/mean). A few interfacial dislocations (IDs) were detected for the 150 mm-diameter epi-wafer by reflection X-ray topography. We have succeeded in removal of IDs by the optimized growth condition.
Role of Cl/Si Ratio in the Low-Temperature Chloro-Carbon Epitaxial Growth of SiC
Authors: Melnychuk Galyna , Kotamraju Siva Prasad , Koshka Yaroslav
Published: March 2013

In order to understand the influence of the Cl/Si ratio on the morphology of the low-temperature chloro-carbon epitaxial growth, HCl was added during the SiCl4/CH3Cl growth at 1300°C. Use of higher Cl/Si ratio allowed only modest improvements of the growth rate without morphology degradation, which did not go far beyond what has been achieved previously by optimizing the value of the input C/Si ratio. On the other hand, when the epitaxial growth process operated at too low or too high values of the input C/Si ratio, i.e., outside of the window of good epilayer morphology, any additional increase of the Cl/Si ratio caused improvement of the epilayer morphology. It was established that this improvement was due to a change of the effective C/Si ratio towards its intermediate values, which corresponded to more favorable growth conditions.
Simulation of Gas-Phase Chemistry for Selected Carbon Precursors in Epitaxial Growth of SiC
Authors: Danielsson Örjan , Sukkaew Pitsiri , Yazdanfar Milan , Kordina Olof , Janzén Erik
Published: March 2013

Numerical simulations are one way to obtain a better and more detailed understanding of the chemical vapor deposition process of silicon carbide. Although several attempts have been made in this area during the past ten years, there is still no general model valid for any range of process parameters and choice of precursors, that can be used to control the growth process, and to optimize growth equipment design. In this paper a first step towards such a model is taken. Here, mainly the hydrocarbon chemistry is studied by a detailed gas-phase reaction model, and comparison is made between C3H8 and CH4 as carbon precursor. The results indicate that experimental differences, which previous models have been unable to predict, may be explained by the new model.
The Nucleation and Propagation of Threading Dislocations with C-Component of Burgers Vector in PVT-Grown 4H-SiC
Authors: Wu Fang Zhen , Dudley Michael , Wang Huan Huan , Byrapa Sha Yan , Sun Shun , Raghothamachar Balaji , Sanchez Edward , Chung Gil Yong , Hansen Darren M. , Mueller Stephan G. , Loboda Mark J.
Published: March 2013

Studies of threading dislocations with Burgers vector of c+a have been carried out using synchrotron white beam X-ray topography. The nucleation and propagation of pairs of opposite sign threading c+a dislocations is observed. Overgrowth of inclusions by growth steps leads to lattice closure failure and the stresses associated with this can be relaxed by the nucleation of opposite sign pairs of dislocations with Burgers vector c+a. Once these dislocations are nucleated they propagate along the c-axis growth direction, or can be deflected onto the basal plane by overgrowth of macrosteps. For the c+a dislocations, partial deflection can occasionally occur, e.g. the a-component deflects onto basal plane while the c-component continuously propagates along the growth direction. One factor controlling the details of these deflection processes is suggested to be related to the ratio between the height of the overgrowing macrostep and that of the surface spiral hillock associated with the threading growth dislocations with c-component of Burgers vector.
Uniformity and Morphology of 10 x 100mm 4° Off-Axis 4H-SiC Epitaxial Layers and their Effect on Device Performance
Authors: Das Hrishikesh , Sunkari Swapna , Oldham Timothy , Rodgers Josh , Casady Janna
Published: March 2013

Homoepitaxial layers with very good thickness and doping uniformity were grown on 4 inch 4˚ off-axis substrates in a 10x100mm planetary reactor. Process optimizations resulted in reduction of the size of the triangular defects. Aggressive pre-etching of the substrate prior to growth resulted in further suppression of the triangular defect concentration from 3-5cm-2 to 0.5cm-2 using the same growth processes. Even imperfect areas of the substrate with scratches show suppressed nucleation of triangular defects. JBS diodes with triangular defects show increased leakage depending on the size of the defects. This effect is more pronounced at higher voltages.
Low Temperature Homoepitaxial Growth of 4H-SiC on 4° Off-Axis Carbon-Face Substrate Using BTMSM Source
Authors: Lee Hun Hee , Seo Han Suk , Lee Do Hyun , Kim Chang Hyun , Kim Hyun Woo , Kim Hyeong Joon
Published: March 2013

Homoepitaxial 4H-SiC thin films were grown on (0 0 0 -1) C-face substrate by cold-wall chemical vapor deposition (CVD) using bis-trimethylsilylmethane (BTMSM, C7H20Si2) precursor. Because of the polarity difference of C-face and (0 0 0 1) Si-face, epitaxial growth conditions of C-face was quite different from those of Si-face. To improve the quality of C-face epitaxial films, effects of epitaxial growth conditions on surface morphology and crystallinity of epitaxial films were investigated.
Innovative 3C-SiC on SiC via Direct Wafer Bonding
Authors: Jennings Michael R. , Pérez-Tomás Amador , Severino Andrea , Ward Peter J. , Bashir Arif , Fisher Craig , Thomas Stephen M. , Gammon Peter Michael , Donnellan Benedict T. , Rong Hua , Hamilton D.P. , Mawby Philip  Andrew
Published: March 2013

In this paper, we report on a novel direct wafer bonding technique; Si (111) wafers to polycrystalline silicon carbide carrier wafers. The purpose of this work is to provide a platform for 3C-SiC epitaxial growth above the wafer bonded Si (111) wafers. We have demonstrated reduced wafer bow, confirmed by optical microscopy together with a digital camera. 3C-SiC epitaxial layers have been grown by conventional chemical vapor deposition techniques above Si/SiC structures. All of these 3C-SiC epitaxial layers are highly crystalline in nature. In the future, the realization of thick, bow-free 3C-SiC layers suitable for power device fabrication is achievable.
Towards Bulk-Like 3C-SiC Growth Using Low Off-Axis Substrates
Authors: Jokubavicius Valdas , Huang Ho Hsuan , Schimmel Saskia , Liljedahl Rickard , Yakimova Rositza , Syväjärvi Mikael
Published: March 2013

Bulk-like 3C-SiC was grown on 1.2 degrees low off-axis 6H-SiC substrates using a sublimation epitaxy technique. The effects of temperature ramp-up and increase in layer thickness on the 3C-SiC domain formation were explored. The temperature ramp-up had no significant effect on the domain size. The domain size was considerably increased and the crystal quality was significantly improved by increasing the thickness of the layer towards bulk-like material. Average full width at half maximum values of 149 arcsec and 65 arcsec were measured in samples with thicknesses of 305 µm and 1080 µm, respectively, at a footprint of 1x3 mm2. This result implies that heteropeitaxial growth of 3C-SiC on low off-axis 6H-SiC substrates by a sublimation method can be used to prepare 3C-SiC seeds or can be further developed for growth of bulk 3C-SiC material.
Color Chart for Thin SiC Films Grown on Si Substrates
Authors: Wang Li , Dimitrijev Sima , Walker Glenn , Han Ji Sheng , Iacopi Alan , Tanner Philip , Hold Leonie , Zhao Yu , Iacopi Francesca
Published: March 2013

In this paper, a color chart was defined for thin SiC films grown on Si substrates. For SiC films thinner than 500 nm, the surface color was observed using an optical microscope with the incident light normally illuminated on the SiC surface. An image of the surface was then taken by a camera attached to the optical microscope and the surface color was defined using RGB code. For SiC films thicker than 500 nm, the image taken by the camera did not represent the real color of the SiC film. Therefore, for these thicker SiC films, the colors were defined by observing the films under daylight fluorescent lighting by naked eyes. It was found that the colors of the SiC films vary periodically as the thickness increased. No color saturation was found for SiC films up to 1185 nm thick.
Defect Generation and Annihilation in 3C-SiC-(001) Homoepitaxial Growth by Sublimation
Authors: Hens Philip , Müller Julian , Wagner Günter , Liljedahl Rickard , Spiecker Erdmann , Syväjärvi Mikael
Published: March 2013

In this paper we present a concept on the defect generation and annihilation during the homoepitaxial growth step of cubic silicon carbide by sublimation epitaxy on templates grown by chemical vapor deposition on silicon substrates. Several structural defects like stacking faults, twins and star defects show opposite evolution from the template layer into the sublimation grown material. While single planar defects tend to annihilate with increasing layer thickness, the defect clusters assigned to the star defects are enlarging. These issues contribute to a balance of how to achieve the best possible quality on thick layers.
Post-Growth Process Effect on Hetero-Epitaxial 3C-SiC Wafer Bow and Residual Stress
Authors: Anzalone Ruggero , Camarda Massimo , Auditore Alessandro , Piluso Nicolò , Severino Andrea , La Magna Antonino , D'Arrigo Giuseppe , La Via Francesco
Published: March 2013

In this paper we study the influence two different post-growth processes on hetero-epitaxial 3C-SiC on Si substrate for 6 and 8 inches wafers. We studied the influence of wafer cutting process and the substrate partially etching. We find an increase of wafer curvature after each cut processes and every etching processes and a correspondent variation of the Raman shift. These result, confirmed by FEM, can be explained in term of the wafer symmetry breaking and the related relaxation under modified constrains due to the cutting and etching. The FEM analysis of the deformation state reveals a modification of the residual stress tensor which changes from a pure biaxial form to a more complicated one.