bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Anti-Rut Agents on Properties of Asphalt Mixture
Authors: Wang Yan Hua , Liu Kuang Yi , Zhang Hai Xia , Li Shan
Published: February 2014

Anti-rut agent, named RPS-3000,was added into AC-25 asphalt mixture and its effects on high temperature stability, low temperature cracking resistance, water damage resistance and fatigue life were investigated in this paper. Results showed that the high temperature stability and low temperature crack resistance of the asphalt mixture improved significantly, the water damage stability increase slightly due to the introduction of anti-rut agents. Besides, the result of fatigue life test presented that excess amount of anti-rut agent may lead a deterioration of fatigue life. Keywords: Anti-rut agent; High temperature stability; Asphalt mixture
Effects of Diffusible Rejuvenator on Properties of Recycled Asphalt Mixture
Authors: Qin De Feng , Yu Jian Ying , Huang Xin
Published: February 2014

The diffusible rejuvenator containing dissolving-diffusing agent was prepared. Effects of the diffusible rejuvenator on properties of recycled asphalt mixture were investigated in comparison with those of common rejuvenator. The results show that the properties of recycled asphalt mixture were significantly improved with the addition of the diffusible rejuvenator due to its good diffusibility. Water stability, low-temperature cracking resistance and fatigue resistance of recycled asphalt mixture are closest to virgin mixture when increasing the diffusible rejuvenator content up to 15 wt%.
Influence of VOC Emission on Asphalt Components
Authors: Zhang Hong Hua , Cui Pei Qiang , Qiu Liu Jing Zi , Wu Shao Peng
Published: February 2014

Volatile organic compounds (VOC) emission from different asphalts not only causes the change in the performances of the bitumen, but also its chemical compositions. This paper carried out four-component analysis to study the influence of VOC emission from different asphalts on bitumens chemical compositions under different conditions. Results show that four-component of asphalts from different places is different. Also as the time of VOC emission increases, the total contents of resins and asphaltenes increase, but the total contents of saturates and aromatics decrease. VOC emission under different temperatures also has a great impact on the asphalt chemical components; Saturates and aromatics decrease in high temperature is larger than in low temperature, and there exists big differences in the asphalt surface layer and the internal of chemical components.
Molecular Simulations of Anti-Aging Mechanisms on Nano-LDHs Modified Asphalt
Authors: Zhou Xin Xing , Zhang Guo Fei , Liu Rong Mao , Zheng Liang
Published: February 2014

Abstract. Aging of asphalt is a serious problem of asphalt damage and occurs throughout its service life. In general, a common method is to use different additives or modifiers for anti-aging. The objective of this study was to investigate the effects of layered double hydroxides(LDHs) additives on anti-aging mechanism using molecular simulations. Molecular dynamic simulations were used to simulate the changes of physical properties and structure before and after aging. Results showed that the degradation of asphalt was dominant reaction and modified asphalts had a high-temperature stability at thermal aging without oxygen. Owing to the difference of polarity between LDHs and asphalt components, phase separation phenomenon would occur at thermal oxidative aging. LDHs also increased the orderliness of asphalt binder.
Performance Evaluation of SBS Modified Bituminous Roofing Membrane Containing Layered Double Hydroxides
Authors: Xu Song , Dan Wei , Li Wen Zu , Yu Jian Ying
Published: February 2014

Layered double hydroxides (LDHs)/SBS modified bitumens used for waterproofing membrane were prepared by melt blending using various contents of SBS and LDHs. Effects of the LDHs on physical properties and thermal oxidative aging performance of modified bitumen were investigated. The results show that softening point and low temperature flexibility of LDHs/SBS modified bitumen are increased simultaneously with the rise of SBS content, while they are little affected by the change of LDHs content. The thermal oxidative aging resistance of SBS modified bitumen is gradually improved with increasing LDHs content. In addition, the aging rate of SBS modified bitumen with LDHs are evidently lower than that without LDHs over time, which indicates that LDHs improve the ability of SBS modified bitumen to resist the thermal oxidative aging effectively.
Research of Coarse Grading Asphalt Mixtures Based on Grey Relational Analysis
Authors: Tu Liang Liang , Zheng Jun , Wu Shao Peng
Published: February 2014

Grey relational analysis (GRA) is an important data handling techniques. In this paper, combining the characteristics of asphalt mixture, the method of GRA is applied to the study of coarse grading. The high temperature stability, low temperature cracking resistance and water stability of asphalt mixture with different grading were evaluated in the laboratory. The results showed that OGFC-25 gradation apply to asphalt mixture that demand high temperature stability. Similarly, ATB-25 gradation benefit low temperature performance and SUP-25 benefit water stability.
Study on Performance of Rubber Powder Modified Asphalt Mixture
Authors: Zhang Yan Shuang , Li Quan Liang , Dong Jian Zhong , Zhang Qing Hu
Published: February 2014

Through the asphalt performance experiment, obtains the best proportion of rubber powder. Through the contrast test of asphalt mixture, the water sensibility, high temperature stability and low temperature stability of asphalt mixture have been studied. Key words: rubber powder modified asphalt asphalt mixture performance study
Effect of Ag Nanoparticles Doped in Polymethyl Methacrylate Matrix for Luminescent Solar Concentrator
Authors: Zhou Wei , He Zhi Qiang , Zhao Xiu Jian
Published: February 2014

Metal-enhanced fluorescence (MEF) of Ag nanoparticles (NPs) in the presence of dye molecules has been studied for application in luminescent solar concentrator (LSC) devices. The LSC was prepared from bulk polymerization reaction of methyl methacrylate (MMA), which was the matrix for the LSC devices. The polymethyl methacrylate (PMMA) sheets doped by different dye concentrations were produced. The optical properties were characterized by absorption, emission and transmission spectroscopy measurements. Effects of dye concentrations on the photovoltaic performance of LSCs were investigated and discussed. Moreover, different concentrations of Ag nanoparticles were dispersed in the matrix in the presence of dye molecules in order to study the metal-enhanced fluorescence in material. The optimal concentration of Ag NPs resulting in a maximum fluorescence emission enhancement (almost 90 %) has been obtained which induced by the particular dye/Ag NPs composite materials. It depends on the coupling and spacing between neighboring dyes and Ag NPs. The result showed that the continuous transition from fluorescence enhancement to quenching, depending on Ag NPs concentration in the LSC device. The highest efficiency (1.96%) was achieved in solar cells which were assembled by the side of the PMMA sheets with dye concentration at 20 ppm.
Environment Impact Analysis of Hollow Brick Produced by Waste in Life Cycle
Authors: Liu Xiao , Gong Xian Zheng , Wang Zhi Hong , Fang Ming Hui
Published: February 2014

This paper uses LCA(Life Cycle Assessment) to make a quantificational analyse for theenvironment impact of hollow brick produced by the waste， the environment impacts come from themining of raw materials to the product process. The results show that the greatest impact on theenvironment is the greenhouse effect in the life cycle of the hollow brick produced by the waste,which possess 24% of the total environmental impact, while the largest environmental impact in thewhole process is sintering the brick, accounting for 73% of the total environmental impact
Life Cycle Assessment of Silicate Cementitious Material Production Using Calcium Carbide Sludge
Authors: Cui Jia Ping , Liu Yu , Wang Zhi Hong , Zhao Li Li , Shi Fei Fei , Hao Li Wei
Published: February 2014

The environmental impacts of cement production using two pre-drying processes, i.e., coal-fired pre-drying process and pre-drying process by waste heat from kiln tail process were analyzed and compared through life cycle assessment (LCA). The results show that the energy consumption, GWP, AP, POCP, HT and EP of pre-drying process by waste heat from kiln tail are about 1%, 2%, 5.2%, 5% ,3.5% and 3.8% lower than coal-fired process; therefore the application of pre-drying process by waste heat from kiln tail has obvious environmental benefits.
Preparation of Core-Shell Structured Ceramsite Containing Soda Residue and its Chloride Ion Release Behavior
Authors: Yan Jian Hua , Zhang Cheng Hao , Cui Su Ping , Rong Gou Hua , Yang Ren Hai , Zhou Peng
Published: February 2014

In this paper, a kind of core-shell structured ceramsite was proposed to reuse the soda residue and to control the chloride ion release, wherein the ceramsite has a core having a high content of soda residue and a vitrified shell. Experimental results showed that the amount of free chloride ions in the mixture containing 58%(by weight) of fly ash, 2%(by weight) of glass powder and 40%(by weight) of soda residue, after being mixed with water at the water/powder ratio of 0.5 and cured at 90% RH, 25°C for 7 days, was found to decrease from 5.92% to 2.84%. That is, the chloride ion was immobilized by the alkali activated fly ash in the mixture and the immobilization rate was as high as 52%. The core-shell structured ceramsite was prepared successfully with the above mixture as the core and the mixture of waste glass powder and shale as the shell and fired at 1120°C for 8 min. No chloride ion was detected in the eluent after the as-prepared ceramsite was soaked in deionized water at 25°C for 24h.
Study on Factors Affecting Dust Removal Efficiency of Asphalt Mixing Plant
Authors: Li Bao Quan , Zhang Qing Hu , Wang Ya Jun , Chen Ju Yong
Published: February 2014

In this paper, LB4000 intermittent asphalt mixing plant was taken as an example to analyze the factors effecting mineral aggregate gradation and mixing quality of batch type asphalt mixing station during production process. And effective measures were put forward to ensure dust removal efficiency, mixture quality and high productivity of mixing station under different working conditions.
Study on Preparation and Application Performance of P-Type Conducting SnO2 Ceramic Target
Authors: Ni Jia Miao , Zhao Xiu Jian , Li Bin Bin , Zheng Min Dong , Peng Ting
Published: February 2014

To obtain high quality SnO2 film, high conductivity and high quality SnO2 target should be obtained first. In this paper, high-conductivity Sb: SnO2 (ATO) ceramic targets were fabricated using SnO2, Sb2O3 powder as raw material. The chemical composition and morphology of SnO2 targets were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). The effect of different forming pressure on the morphology and electrical properties of targets were studied in our paper. The results show that molding pressure has a significant impact on the density of ATO targets and performance during sintering process. When molding pressure is 15 Mpa, the target has the minimum resistivity for 2.38 Ωcm. XRD results show that ATO target possess tetragonal rutile structure with the preferred orientation of (101). XPS indicate that the chemical state of Sn element in the target is Sn4+ and that of Sb is Sb3+. In addition, the shrinkage rate of conductive SnO2 target is 10.34% so that target can be used to sputtering in the magnetron sputter. The preparation process is simple and cost of SnO2 target is low. The transparent conductive SnO2 thin film was successfully deposited on glass substrate with good performance of high hole concentration and low resistivity of 3.334×1019 cm-3 and 3.588 Ω·cm, respectively. The average transmission of p-type SnO2 films was above 80% in the visible light range.
Based on Maturity of Concrete Chloride Ion Diffusion Model and Life Prediction
Authors: Wu Fu Fei , Shi Ke Bin , Dong Shuang Kuai , Wang Guo Wei
Published: February 2014

As chloride ion diffusion in concrete theoretical model without considering the shortcomings of the concrete maturity,the improved maturity model is used to establish the relationship between the diffusion coefficient of concrete maturity. With the mathematical derivation, getting new chloride ion diffusion theoretically, which considers the maturity of the concrete, the chloride ion binding capacity, the degradation effects of chlorine ion diffusion equation,and consequently broadens the scope of the fick's second law of diffusion, besides, its form and solution completely consistent with the one in the second law of fick equation. By the calculation example,it can be found that the model is more accurate than the traditional ones, and it also applies to the high content of high-performance concrete.
Properties and Microstructure of HPC with Lithium-Slag and Fly Ash
Authors: Wu Fu Fei , Shi Ke Bin , Dong Shuang Kuai
Published: February 2014

High performance concrete (HPC) was prepared using lithium-slag and fly ash,which are the industrial waste in Xinjiang Province,China,and its mechanical properties,crack resistance impermeability of concrete. The results showed that: lithium slag can well improve the mechanical properties of concrete, after adding fly ash, in the total dosage of 20%, the improving effect on the mechanical properties is the best; in the total dosage of 50%, its performance improvement of cracking resistance and impermeability is particularly evident, and can significantly improve the interface of concrete structures and products. At early hydration, admixture involved secondary hydration reaction generated in the interface area silicon ratio of calcium silicate hydrate and dense structure,which reduces the crystal content of loose AFt and Ca(OH)2, improving the performance of concrete mechanical and impermeability, particularly, the formation of needle AFt compensate the shrinkage of concrete and improve the performance of concrete early cracking.
Study on Mechanical and Thermal Properties of Graphite Modified Cement Concrete
Authors: Wu Shao Peng , Wang Peng , Li Bo , Pang Ling , Guo Fei
Published: February 2014

The comprehensive survey on the thermal conductive cement concrete consists of graphite is obtained in this paper. The effects of graphite on mechanical properties and thermal properties were investigated to determine the optimum materials design. Additionally, scanning electron microscopy (SEM) was used to elucidate micrographs of the fracture graphite modified cement concrete. Result indicated that graphite could greatly improve the thermal conductivity properties of cement concrete, but degrade the related compressive strength simultaneously. When the graphite content is 15%, the increment of the thermal conductivity was 50% while the reduction of the compressive strength was almost 90%. Furthermore, SEM images illustrated that the reason for the degradation of mechanical strength maybe depend on the flake structure of graphite.
Modeling of High Performance 4H-SiC Emitter Coupled Logic Circuits
Authors: Singh Shakti , El Sayed Nourhan , Elgabra Hazem , ElBoshra Tamador , Wahbah Maisam , Al Zaabi Mariam
Published: February 2014

SiC, a wide band gap semiconductor, is capable of robust operation at temperatures well above 600°C. SiC bipolar transistors are well suited for applications at high temperatures as, unlike MOSFET, it does not have a critical gate oxide, and hence oxide reliability at high temperatures is not an issue. In this paper, the design of optimized emitter coupled logic technology circuits using 4H-SiC bipolar transistors is presented. The circuits work over a wide range of temperatures and power supply voltages at high speeds, demonstrating the potential of robust high speed ECL integrated circuits in SiC for small-scale logic applications.
Characterization of 4H-SiC Bipolar Junction Transistor at High Temperatures
Authors: Zhang Nuo , Rao Yi , Xu Nuo , Maralani Ayden , Pisano Albert P.
Published: February 2014

In this work, a 4H-Silicon Carbide (SiC) Bipolar Junction Transistor (BJT) capable of operating at high temperatures up to 673 K is demonstrated. Comprehensive characterization including current gain, early voltage, and intrinsic voltage gain was performed. At elevated temperatures, although the current gain of the device is reduced, the intrinsic voltage gain increases to 5900 at 673 K, suggesting 4H-SiC BJT has the potential to be used as a voltage amplifier at extremely high temperatures.
Stability of Current Gain in SiC BJTs
Authors: Buono Benedetto , Allerstam Fredrik , Domeij Martin , Konstantinov Andrei , Gumaelius Krister , Das Hrishikesh , Neyer Thomas
Published: February 2014

In this work, large area SiC BJTs with good long-term stability in 1000 hrs DC stress tests are demonstrated. It is also illustrated how wafer scanning techniques can be used to reject BJT dies with basal plane dislocations, thereby eliminating the risk for bipolar degradation.
Optical Triggering of High Current (1300 A), High-Voltage (12 kV) 4H-SiC Thyristor
Authors: Rumyantsev Sergey , Levinshtein Michael E. , Shur Michael , Cheng Lin , Agarwal Anant K. , Palmour John W.
Published: February 2014

A 12 kV class 4H-SiC thyristor with a pilot thyristor (an amplification step) has been triggered to a current Imax = 1310 A in a mixed resistive-inductive load circuit. In order to further increase the Imax, the homogeneity of the initially turned-on region should be improved and/or additional amplification steps introduced
20 kV 4H-SiC N-IGBTs
Authors: Ryu Sei Hyung , Capell Craig , Jonas Charlotte , O'Loughlin Michael  J. , Clayton Jack , van Brunt Edward , Lam Khiem , Richmond Jim , Kadavelugu Arun , Bhattacharya Subhashish , Burk Albert A. , Agarwal Anant , Grider Dave , Allen Scott T. , Palmour John W.
Published: February 2014

A 1 cm x 1 cm 4H-SiC N-IGBT exhibited a blocking voltage of 20.7 kV with a leakage current of 140 μA, which represents the highest blocking voltage reported from a semiconductor power switching device to this date. The device used a 160 μm thick drift layer and a 1 μm thick Field-Stop buffer layer, and showed a VF of 6.4 V at an IC of 20 A, and a differential Ron,sp of 28 mΩ-cm2. Switching measurements with a supply voltage of 8 kV were performed, and a turn-off time of 1.1 μs and turn-off losses of 10.9 mJ were measured at 25°C, for a 8.4 mm x 8.4 mm device with 140 μm drift layer and 2 μm F-S buffer layer. The turn-off losses were reduced by approximately 50% by using a 5 μm F-S buffer layer. A 55 kW, 1.7 kV to 7 kV boost converter operating at 5 kHz was demonstrated using the 4H-SiC N-IGBT, and an efficiency value of 97.8% was reported.
On the TCAD Based Design Diagnostic Study of 4H-SiC Based IGBTs
Authors: Nawaz Muhammad , Chimento Filippo
Published: February 2014

This paper addresses the design diagnostic study of 4H-SiC based IGBTs using two dimensional numerical computer simulations. Using identical set of physical device parameters (doping, thicknesses), simulated structure was first calibrated 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 decay in the device transconductance and threshold voltage is observed with increasing temperature. The 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 K) due to decrease in the carrier mobility. The design of buffer layer is investigated that shows lower on-state losses with thin high doped buffers. For the design of devices over 15 20 kV, the design of drift layer demands a doping of < 2.0 x 1014 cm-3 with epitaxial layer quality giving a carrier life time over 2.0 μs.
Radiation-Induced Currents in 4H-SiC Dosimeters for Real-Time Gamma-Ray Dose Rate Monitoring
Authors: Fujita Natsuko , Iwamoto Naoya , Onoda Shinobu , Makino Takahiro , Ohshima Takeshi
Published: February 2014

In order to test the response of radiation-induced current with wide range of dose rate, a Silicon Carbide (SiC) dosimeter is exposed to gamma-rays emitted from a 60Co source. The SiC dosimeter in this study is made of a high purity semi-insulating 4H-SiC with nickel and aluminum electrodes. We have successfully demonstrated that the radiation-induced currents in the dosimeter show a linear relationship with the dose rate, and are repeatable and stable.
Optical and Electrical Simulations of Solar Cell Based on Silicon and Silicon Carbide
Authors: Biondo Stéphane , Vervisch Wilfried , Ottaviani Laurent
Published: February 2014

Among the different ways to improve the performances of light harvesting inside solar cells, multilayer configuration can be used. The bandgap of each single layer will contribute to absorption in a well defined wave-lengths range, enhancing the overall performances. Here, we investigate such performances in the case of solar cells made by two layers: a silicon one, and a SiC-based layer, and show the increasing of electrical working by means of computer simulations. These simulations are based on Finite Difference Time Domain (FDTD) for the optical calculations, on one side, and the Finite Element Method (FEM) for the electrical ones, on the other. The main goal is to show the enhancement of the electrical performances in heterostructure solar cells. In this paper, we investigate the influence of each different structure on the optical and electrical response. Our results show the influence of the device structures, in particular, the enhancement of the UV-ligth absorption inside the solar cell. Moreover, the difference structures allow us to show an improvement in the harvesting charge carrier by the heterojunction.
High Temperature Hydrogen Sensor Based on Silicon Carbide (SiC) MOS Capacitor Structure
Authors: Ofrim Bogdan , Brezeanu Gheorghe , Draghici Florin , Rusu Ion
Published: February 2014

MOS capacitor devices based on silicon carbide (SiC) are largely used as hydrogen detectors in high temperature and chemically reactive environments. A SiC MOS capacitor structure used as hydrogen sensor is analyzed by extensive simulations. The sensitivity to hydrogen detection, stability to temperature variation and dependence on interface states concentration are evaluated. The effects of structure parameters on sensors performance are also investigated. Results show that the oxide layer type and thickness and the SiC polytype have a significant influence on the detectors performance. The proposed optimum structure for high temperature hydrogen detection is based on 3C-SiC substrate and 10nm TiO2 layer. In accordance with the simulations results, three types of masks are designed for the fabrication of SiC MOS capacitor structures.
Progress in High Voltage SiC and GaN Power Switching Devices
Authors: Chow T. Paul
Published: February 2014

The present status of the development and commercialization of SiC and GaN power devices for power electronics applications is presented. The technology obstacles and needs as well as future trend in these power devices are also discussed.
Strategic Overview of High-Voltage SiC Power Device Development Aiming at Global Energy Savings
Authors: Cheng Lin , Palmour John W. , Agarwal Anant K. , Allen Scott T. , Brunt Edward V. , Wang Gang Yao , Pala Vipindas , Sung Woong Je , Huang Alex Q. , O'Loughlin Michael  J. , Burk Albert A. , Grider David E. , Scozzie Charles
Published: February 2014

Advanced high-voltage (≥10 kV) silicon carbide (SiC) devices described in this paper have the potential to significantly impact the system size, weight, high-temperature reliability, and cost of modern variable-speed medium-voltage (MV) systems such as variable speed (VSD) drives for electric motors, integration of renewable energy including energy storage, micro-grids, traction control, and compact pulsed power systems. In this paper, we review the current status of the development of 10 kV-20 kV class power devices in SiC, including MOSFETs, JBS diodes, IGBTs, GTO thyristors, and PiN diodes at Cree. Advantages and weakness of each device are discussed and compared. A strategy for high-voltage SiC power device development is proposed.
SiC Power Module for Compact Power Conversion Equipment
Authors: Yamashita Kenya , Kato Keishi , Ikeuchi Hiroki , Tanaka Junya , Toyota Kei , Nakamura Taichi , Takahashi Keiko , Arakawa Ryutaro , Sasaoka Tatsuo
Published: February 2014

In order for wide bandgap semiconductor power devices to be practical use in various power electronics applications, a 2in1 600V75A power package with a 200 degree Celsius heat resistance was newly developed on the premise of mass production. This package designed to specify a low inductance of less than 24nH enables SiC and GaN-based devices to be driven with a high slew rate up to 5kA/us under hard-switching condition. Furthermore, this package encapsulated by a epoxy resin of a high heat resistance and equipped with thick Cu heat spreader allow these power devices to be driven up to 200 degree Celsius and dissipate heat in large quantities (thermal resistance Rth,jc: 0.6K/W), which is found to make cooling heat sink simplified. We introduced 50ASiC-MOSFET in this package, and verified the operation on a power conditioner for Solar Photovoltaic cells up to 4kW output. A high power conversion efficiency of 97.7% was measured by our SiC power packages on downsized cooling heat sink in 1/4 volume, which was more efficient than Si-IGBT module by 1.5%.
SiC Power Devices as Enabler for High Power Density - Aspects and Prospects
Authors: Friedrichs Peter
Published: February 2014

Comparable to silicon the main way to improve the cost performance of SiC power devices is to go up with current density since the main selling point of a power device is its current handling capability. To follow this path successfully a couple of application and system relevant aspects should be taken into account beside the pure focus on reducing nominal or absolute losses at chip level. This paper will address some of those topics in combination with discussing state of the art device technologies on SiC. Also some considerations regarding the operation of SiC devices at elevated temperatures will be given, mainly targeting for increased power density and reduced losses in power electronic systems.
Research of Silver Sintering Process and Reliability for High Temperature Operation of SiC Power Devices
Authors: Zhang Zhe , Nakamura Takashi , Hanada Toshio
Published: February 2014

In order to take full advantage of the high power density available by the packaging of SiC devices, this group has been exploring die attachment methods based on the sintering of silver particles between the device and Silver-plated Cu substrates with void free results. We have also extended this capability from not only attaching single chips assembled in TO-247 packages but also to multiple chips attached at once on a copper substrate. This multi-chip processing capability will aid in further development of SiC power modules.
Carrier Mobility as a Function of Temperature in as-Grown and H-Intercalated Epitaxial Graphenes on 4H-SiC
Authors: Winters Michael , Thorsteinsson E.B. , Sveinbjörnsson E.Ö. , Gislason H.P. , Hassan Jawad , Janzén Erik , Rorsman Niklas
Published: February 2014

The carrier velocity is measured as a function of electric field in as-grown and H-intercalaed epitaxial graphene grown on semi-insulating 4H-SiC in order to estimate the low field carrier mobility as a function of temperature. The mobility is also measured on the same samples as a function of temperature in a liquid Helium (He) cooled cryostat. The two temperature dependent measurements are compared in order to deduce the dominant carrier scattering mechanisms in both materials. In as-grown material, acoustic phonon scattering and impurity scattering both contribute, while impurity scattering dominates in H-intercalated material.
Formation of Graphene onto Atomically Flat 6H-SiC
Authors: Rius Gemma , Mestres Narcis , Tanaka Yayoi , Miyazaki Hidetoshi , Eryu Osamu , Godignon Philippe
Published: February 2014

SiC crystal is a wide band gap material of high hardness and chemical inertness. Graphene is nowadays a ubiquitous 2D material that would revolutionize many applications. Combining the characteristics of SiC and graphene higher performance and efficiency are expected, e.g. for high frequency electronic devices. The obtaining of graphene directly on SiC substrates by a single step thermal decomposition process is promising, but optimal standardized conditions are not established. We present the use of chemical-mechanical polishing (CMP) as a pre-graphene growth SiC conditioning to enable deep comprehension of the mechanisms of SiC decomposition and control towards selective formation of graphene.
Planarization of the Gallium Nitride Substrate Grown by the Na Flux Method Applying Catalyst-Referred Etching
Authors: Yamaguchi Wataru , Sadakuni Shun , Isohashi Ai , Asano Hiroya , Sano Yasuhisa , Imade Mamoru , Maruyama Mihoko , Yoshimura Masashi , Mori Yusuke , Yamauchi Kazuto
Published: February 2014

In this study, a gallium nitride (GaN) substrate grown by the Na flux method was processed by catalyst-referred etching (CARE). CARE process for GaN involves two-step: the first step uses the photoelectrochemical process (PEC-CARE) and the second step applies a platinum (Pt) catalyst (Pt-CARE). PEC-CARE can produce a highly ordered GaN (0001) surface. The surface roughness was 0.638 nm root-mean-square (rms). Pt-CARE can produce an atomically flat surface with a step-terrace structure on the entire surface. The surface roughness was 0.113 nm rms. The removal rates of PEC-CARE and Pt-CARE were found to be 45.5 and 5.5 nm/h, respectively.
4H-SiC Epitaxial Layer Grown on 150 mm Automatic Horizontal Hot Wall Reactor PE106
Authors: Mauceri Marco , Pecora Antonino , Litrico Grazia , Vecchio Carmelo , Puglisi Marco , Crippa Danilo , Piluso Nicolo’ , Camarda Massimo , La Via Francesco
Published: February 2014

Preliminary results of 150mm SiC 4H 4°off have been obtained with the new 150mm automatic horizontal hot wall reactor PE1O6, using chlorinated chemistry (SiHCl3 + C2H4). A new injection system has been tested in two configurations and results will be shown in this paper. AFM surface roughness measurements and epi defect density have been reported.
Homo-Epitaxial Growth on Low-Angle Off Cut 4H-SiC Substrate
Authors: Li Xun , Janzén Erik , Henry Anne
Published: February 2014

The growth of 4H-SiC epilayers on 1.28o off-cut substrates is reported in this study and comparison when using standard 4o and 8o off-cut substrates is added. Growth at high temperature is needed for the polytype stability, whereas low C/Si is requested to decrease both triangular defects density and roughness of the grown surface. An in-situ etching with Si rich ambient allows the growth of epilayers with specular surface. The formation of Si droplets can be observed on the grown surfaces when lowering the growth temperature and appears first for the high off-cut angle.
Epitaxial Growth of Thick Multi-Layer 4H-SiC for the Fabrication of Very High-Voltage C-Face n-Channel IGBT
Authors: Miyazawa Tetsuya , Ji Shi Yang , Kojima Kazutoshi , Ishida Yuuki , Nakayama Koji , Tanaka Atsushi , Asano Katsunori , Tsuchida Hidekazu
Published: February 2014

The epitaxial growth of thick multi-layer 4H-SiC to fabricate very high-voltage C-face n-channel IGBTs is demonstrated using 3-inch diameter wafers. We employ an inverted-growth process, which enables the on-state voltage of resultant IGBTs to be reduced. Furthermore a long minority carrier lifetime (> 10 μs) and a low-resistance p+ epilayer can reduce the forward voltage drop of the IGBTs. The small forward voltage drop is demonstrated particularly at high temperatures by fabricating and characterizing simple pin diodes using the epi-wafer.
An Approach to Trace Defects Propagation during SiC Epitaxy
Authors: Fan Ya Ming , Zhang Li Guo , Wang Jie , Zhang Xue Min , Zhang Ze Hong , Zhang Bao Shun , Sudarshan Tangali S.
Published: February 2014

In this work, the generation of in-grown SFs, half-moon defects, and carrot defects in SiC epilayer is studied by using epitaxy-etch-epitaxy approach. It is found that under our growth conditions, most of these defects have a similar origin, and they nucleate at obstacles to step flow at the SiC substrate/epilayer interface. These obstacles may be micropipes, scratches, or foreign particles on the substrate surface.
Characterization of the Defect Evolution in Thick Heavily Al-Doped 4H-SiC Epilayers
Authors: Ji Shi Yang , Kojima Kazutoshi , Ishida Yuuki , Yamaguchi Hirotaka , Saito Shingo , Kato Tomohisa , Tsuchida Hidekazu , Yoshida Sadafumi , Okumura Hajime
Published: February 2014

The defect evolution on 90 μm-thick heavily Al-doped 4H-SiC epilayers with Al doping level higher than 1020 cm-3 was studied by tracing back to initial growth stage to monitor major dislocations and their propagations in each growth stage. Results from X-ray topography and KOH etching demonstrate that all existing dislocations on the surface of 90 μm-thick epilayer can be identified as the defects originating from substrate. In other words, there seems no new dislocation generated after a long-term growth. Nevertheless, a high density of misfit dislocation was found appearing near the substrate/epilayer interface for epilayer with Al doping level of 3.5×1020 cm-3, while misfit dislocation cannot be seen on epilayer with Al doping level of 1.5×1020 cm-3.
Crystal Growth of Highly Oriented Silicon Carbide by Chemical Vapor Deposition with Alternating Gas Supply
Authors: Nagano Takayuki , Sato Koji
Published: February 2014

Silicon carbide (SiC) film on silicon (Si) was synthesized by chemical vapor deposition (CVD) with concurrent gas supply and alternative gas supply. The alternative gas supply method was very effective to improve the crystallinity of silicon carbide at the same experimental condition. The crystallinity was sensitive for source gas concentration and background pressure.
Effect of Process Parameters on Dislocation Density in Thick 4H-SiC Epitaxial Layers Grown by Chloride-Based CVD on 4° Off-Axis Substrates
Authors: Yazdanfar Milan , Pedersen Henrik , Kordina Olof , Janzén Erik
Published: February 2014

The effect of process parameters such as growth temperature, C/Si ratio, etching time, and Si/H2 ratio on dislocation density was investigated by performing KOH etching on 100 μm thick epitaxial layers grown on 4° off axis 4H-SiC substrates at various growth conditions by a chemical vapor deposition (CVD) process using a chloride-based chemistry to achieve growth rates exceeding 100 μm/h. We observe that the growth temperature and the growth rate have no significant influence on the dislocation density in the grown epitaxial layers. A low C/Si ratio increases the density of threading screw dislocations (TSD) markedly. The basal plane dislocation (BPD) density was reduced by using a proper in-situ etch prior to growth.
Demonstration of High Quality 4H-SiC Epitaxy by Using the Two-Step Growth Method
Authors: Mitani Yoichiro , Tomita Nobuyuki , Hamano Kenichi , Tarutani Masayoshi , Tanaka Takanori , Ohno Akihito , Kuroiwa Takeharu , Toyoda Yoshihiko , Imaizumi Masayuki , Sumitani Hiroaki , Yamakawa Satoshi
Published: February 2014

A new growth method for considerably suppressing generation of carrot and triangle defects is presented. Based on the investigation for the surfaces before and after the epitaxial growth, it becomes clear that those defects were results from micrometer-scale SiC particles. For removing the particles, pre-flow of H2 at high temperature before the growth was very effective. The density of those defects strongly depends on the condition of the pre-flow and especially decreased at Tp=1575°C and tp=180 sec.
Development of RAF Quality 150mm 4H-SiC Wafer
Authors: Kondo Hiroyuki , Takaba Hidetaka , Yamada Masanori , Urakami Yasushi , Okamoto Takeshi , Kobayashi Masakazu , Masuda Takashi , Gunjishima I. , Shigeto K. , Ooya Nobuyuki , Sugiyama Naohiro , Matsuse Akihiro , Kozawa T. , Sato Takayuki , Hirose Fusao , Yamauchi Shoichi , Onda Shoichi
Published: February 2014

We have developed RAF (Repeated a-face) growth method which is high quality bulk crystal growth technology [1, 2]. A block crystal more than 150 mm square size was produced by the RAF growth method. Since c-face growth crystal was produced on the seed obtained from the block crystal, high quality 150mm 4H-SiC wafer was achieved. This paper reports the results of the quality evaluation.
Ge Assisted SiC Epitaxial Growth by CVD on SiC Substrate
Authors: Alassaad Kassem , Soulière Véronique , Doisneau Beatrice , Cauwet François , Peyre Hervé , Carole Davy , Chaussende Didier , Ferro Gabriel
Published: February 2014

This paper presents the results obtained after chemical vapor deposition of SiC with the addition of GeH4 gas to the classical SiH4+C3H8 precursor system. Epitaxial growth was performed either on 8°off-axis or on-axis 4H-SiC substrate in the temperature range 1500-1600°C. In the off-axis case, the layer quality (surface morphology and defect density) does not change though accompanied with Ge droplets accumulation at the surface. The Ge incorporation level was found to increase with temperature in the 1017 1018 cm-3 ranges. It was observed that adding GeH4 leads to the increase of the n type doping level by a factor from 2 to 5 depending on the C/Si ratio. In the on-axis case, GeH4 was only added to the gas phase before starting the SiC growth. It was found that there is a conditions window (temperature and GeH4 flux) for which 3C-SiC twin free layers can be grown. Adding this foreign element before SiC growth clearly modifies SiC nucleation on on-axis substrate.
4H-SiC Epitaxial Growth on C-Face 150 mm SiC Substrate
Authors: Miyasaka Akira , Norimatsu Jun , Fukada Keisuke , Tajima Yutaka , Kageshima Yoshiaki , Muto Daisuke , Odawara Michiya , Okano Taichi , Momose Kenji , Osawa Yuji , Osawa Hiroshi , Sato Takayuki
Published: February 2014

The production of 150 mm-diameter SiC epitaxial wafers is the key to the spread of SiC power devices. We have developed production technology of the epitaxial growth for 4° off Carbon face (C-face) 4H-SiC epitaxial layers on 150 mm diameter substrates. Several growth parameters and hardware were optimized to obtain high uniformity wafers. We have succeeded in fabricating high quality C-face wafers with smooth surface and high uniformity.
First-Principles Study of Nanofacet Formation on 4H-SiC(0001) Surface
Authors: Sawada Keisuke , Iwata Jun Ichi , Oshiyama Atsushi
Published: February 2014

We perform the first-principles calculations on the 4H-SiC(0001) surface and clarify the
mechanism of the facet formation. We first identify atomic structures of single-, double- and quadribilayer
steps and find that the single-bilayer (SB) step has the lowest total energy among these three
step structures. Then, we reveal that the nanofacet consisting of SB steps is more energetically stable
than the equally spaced SB step and the surface-energy variation caused by the difference of stacking
sequences of the bi-atomic layer near the surface is an important factor of the facet formation.
HCl Assisted Growth of Thick 4H-SiC Epilayers for Bipolar Devices
Authors: Kallinger Birgit , Ehlers Christian , Berwian Patrick , Rommel Mathias , Friedrich Jochen
Published: February 2014

The addition of hydrogen chloride (HCl) to our conventional CVD process allows for high growth rates up to 50 μm/h while maintaining the step-flow growth mode. Such epilayers exhibit quite low total concentrations of point defects less than 2 x 1013 cm-3. But, the HCl addition shows an ambivalent influence on the concentration of the lifetime killer defect Z1/2. For low growth rates, the Z1/2 concentration slightly decreases with increasing HCl addition. For higher growth rates, the Z1/2 concentration increases with increasing HCl addition.
Homo-Epitaxial Growth on 2° Off-Cut 4H-SiC(0001) Si-Face Substrates Using H2-SiH4-C3H8 CVD System
Authors: Tamura Kentaro , Kudou Chiaki , Masumoto Keiko , Nishio Johji , Kojima Kazutoshi
Published: February 2014

We have grown epitaxial layers on 2° off-cut 4H-SiC(0001) Si-face substrates. The epitaxial layer surfaces on 2° off-cut substrates are more prone to generate step-bunching than on 4° off-cut substrates, which are observed by confocal microscopy with differential interference contrast. We have speculated that the step-bunching is generated at the beginning of an epitaxial growth. Triangular defect density of epitaxial layers on 2° off-cut substrates is as low as 0.7 cm–2 for the size corresponding to 150 mm. We have firstly reported distribution of 2° off-cut epitaxial layers for the 150-mm size using two 76.2-mm wafers: σ/mean = 3.3% for thickness, σ/mean = 7.3% for carrier concentration.
Heteroepitaxial CVD Growth of 3C-SiC on Diamond Substrate
Authors: Soulière Véronique , Vo-Ha Arthur , Carole Davy , Tallaire Alexandre , Brinza Ovidiu , Pinero Jose Carlos , Araujo Daniel , Ferro Gabriel
Published: February 2014

This work presents the successful CVD heteroepitaxial growth of 3C-SiC on diamond (100) substrates. When performing a direct SiC growth at 1500°C on such substrate, it leads to polycrystalline deposit. The use of a substrate pretreatment involving silicon deposition allows forming a more continuous and smoother layer. Electron BackScatter Diffraction and Transmission Electron Microscopy all revealed that the 3C-SiC layer grown on the (100) diamond substrate is monocrystalline and well oriented.
Optical Investigation of 3C-SiC Hetero-Epitaxial Layers Grown by Sublimation Epitaxy under Gas Atmosphere
Authors: Kwasnicki P. , Jokubavicius V. , Sun J.W. , Peyre Hervé , Yakimova R. , Syväjärvi Mikael , Camassel Jean , Juillaguet Sandrine
Published: February 2014

We investigated three 3C-SiC samples grown on 6H SiC substrate by sublimation epitaxy under gas atmosphere. We focus on the low temperature photoluminescence and Raman measurements to show that compare to a growth process under vacuum atmosphere, the gas atmosphere favor the incorporation of impurities at already existing and/or newly created defect sites.
Formation of an Interfacial Buffer Layer for 3C-SiC Heteroepitaxy on AlN/Si Substrates
Authors: Meguro Kazuki , Narita Tsugutada , Noto Kaon , Nakazawa Hideki
Published: February 2014

We have formed a SiC interfacial buffer layer on AlN/Si substrates at a low temperature by low-pressure chemical vapor deposition (LPCVD) using monomethylsilane (CH3SiH3; MMS), and grew 3C-SiC films on the low-temperature buffer layer by LPCVD using MMS. We investigated the surface morphology and crystallinity of the grown SiC films. It was found that the formation of the SiC buffer layer suppressed the outdiffusion of Al and N atoms from the AlN intermediate layer to the SiC films and further improved the surface morphology and crystallinity of the films.
Annealing of Electron Irradiated, Thick, Ultrapure 4H SiC between 1100°C and 1500°C and Measurements of Lifetime and Photoluminescence
Authors: Klahold Walter M. , Devaty Robert P. , Choyke Wolfgang J. , Kawahara Koutarou , Kimoto Tsunenobu , Ohshima Takeshi
Published: February 2014

Ultra-pure n-type (8×1013 cm-3), 99 μm thick epitaxial films of 4H SiC were electron irradiated at 170 keV with a fluence of 5×1016 cm-2 or at 1 MeV with a fluence of 1×1015 cm-2 in various geometries. Low temperature photoluminescence (LTPL) spectra and microwave photoconductance (μPCD) lifetime measurements were obtained on all samples prior to annealing and after annealing in Argon in free standing mode or on a POCO carbon platform, every 50°C from 1100°C to 1500°C. No improvement in carrier lifetime was obtained. Spurious lines attributable to the use of a Genesis CX 3550Å laser are also reported.
Identification of Structures of the Deep Levels in 4H-SiC
Authors: Nakane Hiroki , Kato Masashi , Ichimura Masaya , Ohshima Takeshi
Published: February 2014

We investigated annealing behavior of the carrier lifetime and the deep levels in electron irradiated n-type and semi-insulating 4H-SiCs. We observed two peaks for each sample by photo induced current transient spectroscopy (PICTS) measurements, and their heights depended on annealing temperature. By comparing the annealing behavior of the peak height with reported temperature dependence of concentrations of various defects, we speculated that the observed peaks originate from either VSiVC, CSiVC or EI4.
Defect Levels in High Purity Semi-Insulating 4H-SiC Studied by Alpha Particle Induced Charge Transient Spectroscopy
Authors: Iwamoto Naoya , Onoda Shinobu , Fujita Natsuko , Makino Takahiro , Ohshima Takeshi
Published: February 2014

Defect levels in high purity semi-insulating 4H silicon carbide substrates are studied by charge transient spectroscopy using 5.5 MeV alpha particles. A shallow defect level with the activation energy around 0.3 eV is found in all samples annealed at temperatures from 1400 to 1600 °C. Some other defect levels lying at deeper in the bandgap are found in samples annealed at 1400 and 1500 °C. As these deep levels are annealed out by 1600 °C, the series resistance of samples is decreased.
Comparison of Carrier Lifetime Measurements and Mapping in 4H SiC Using Time Resolved Photoluminscence and μ-PCD
Authors: Kallinger Birgit , Rommel Mathias , Lilja Louise , Hassan Jawad , Booker Ian D. , Janzén Erik , Bergman J. Peder
Published: February 2014

Carrier lifetime measurements and wafer mappings have been done on several different 4H SiC wafers to compare two different measurement techniques, time-resolved photoluminescence and microwave induced photoconductivity decay. The absolute values of the decay time differ with a factor of two, as expected from recombination and measurement theory. Variations within each wafer are comparable with the two techniques. Both techniques are shown to be sensitive for substrate quality and distribution of extended defects.
Interaction between Vapor Species and Graphite Crucible during the Growth of SiC by PVT
Authors: Ariyawong Kanaparin , Tsavdaris Nikolaos , Dedulle Jean Marc , Sarigiannidou Eirini , Ouisse Thierry , Chaussende Didier
Published: February 2014

Graphite crucible in seeded sublimation growth of Silicon Carbide (SiC) single crystal does not only act as a container but also as an additional carbon source. The modeling of the growth process integrated with the etching phenomenon caused by the interaction between vapor species and the graphite crucible is shown to be able to predict the shape of the crystal front during the growth. The additional fluxes produced at the graphite part are delivered to the growing crystal mainly at the crystal periphery. The results obtained from the modeling are in good agreement with the experimental ones.
Photoluminescence Imaging and Discrimination of Threading Dislocations in 4H-SiC Epilayers
Authors: Nagano Masahiro , Kamata Isaho , Tsuchida Hidekazu
Published: February 2014

This paper demonstrates high-resolution photoluminescence (PL) imaging and discrimination of threading dislocations in 4H-SiC epilayers. Threading screw dislocations (TSDs) and TEDs are distinguished by differences in PL spot size and spectrum. We found that TEDs are further discriminated into six types according to their Burgers vector directions by the appearance of PL imaging. Cross-sectional PL imaging reveals inclination angles of threading dislocations across a thick epilayer.