bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of Gas Atomized Ti-6Al-4V Powders for Additive Manufacturing
Authors: Tshabalala Lerato Criselda , Mathe-Maleboho Ntombizodwa , Chikwanda Hilda
Published: June 2018

In this paper, titanium powders from various sources were characterized to compare powder intergrity for additive manufacturing by selective laser melting process. Selective laser melting by powder-bed based Additive Manufacturing (AM) is an advanced manufacturing process that bonds successive layers of powder by laser melting to facilitate the creation of engineering components. This manufacturing approach facilitates the production of components with high geometrical complexity that would otherwise be impossible to create through conventional manufacturing processes. Although the use of powder in AM is quite common, powder production and optimization of powder properties to yield desired performance characteristics has posed a serious challenge to researchers. It is therefore critical that powder properties be studied and controlled to ensure reliability and repeatability of the components that are produced. Typically, the desired feature of high quality titanium metal powders for AM are a combination of high sphericity, density and flowability. Scanning electron microscopy, EDS, particle size distribution and powder rheology were extensively performed to investigate the properties of gas-atomized Ti-6Al-4V powders.
The Effect of Heat Treatments on Microstructure and Mechanical Properties of As-Extruded Ti-6Al-4V Alloy Rod from Blended Elemental Powders
Authors: Romero Villarreal Carlos , Yang Fei , Raynova Stiliana , Bolzoni Leandro
Published: June 2018

In this study, Ti-6Al-4V bars were first prepared by extrusion of powder compacts from blended powder mixtures in the beta phase region, then the as-extruded bars were heat-treated following four different conditions: beta quenching and aging (βQA), broken up structure (BUS) treatment, solution treatment and aging (STA) and recrystallization annealing (RA). The effect of the heat treatments on microstructure and mechanical properties was studied using optical microscopy, scanning electron microscopy, and mechanical test to determine which heat-treatment condition has the greatest impact on the mechanical properties of the as-extruded Ti-6Al-4V alloy. The results show that the as-extruded condition has the best balance of strength (1120 MPa of UTS) and ductility (11% of elongation to failure). βQA and STA lead to a slight increase in strength but ductility decreases considerably. After BUS and RA treatments, both strength and ductility are reduced. The relationship between processing, microstructure and properties was studied, and their implications towards fatigue behaviour and fracture toughness were discussed.
Development of Bio-Compatible Beta Ti Alloy Powders for Additive Manufacturing for Application in Patient-Specific Orthopedic Implants
Authors: Ivanov Eugene , del Rio Eduardo , Kapchemnko Igor , Nyström Maija , Kotila Juha
Published: June 2018

The use and application of alloys as biomedical alloys have increased over the past few years owing to their excellent biocompatibility, corrosion resistance, high mechanical and fatigue resistance, low density, adequate wear resistance, and low elastic modulus. Orthopedic implant materials are exposed to high mechanical loading. Conventional materials based on Ti-6Al-4V, stainless steel or cobalt-chromium alloys demonstrate good mechanical strength, but also some toxicological concerns due to release of toxic elements which may result in inflammatory reactions. Metal alloys based on titanium, zirconium, tantalum and niobium represent higher biocompatibility with appropriate mechanical properties for avoiding stress-shielding and consecutive implant loosening. Application of specifically designed spherical β-titanium alloy powders in additive manufacturing, such as selective laser melting (SLM) or electron beam melting (EBM); enable the production of components with a high degree in freedom of design. Accordingly, SLM or EBM of Ti/Nb (/Ta) alloys offer the possibility to fabricate patient-specific orthopedic implants. The present paper describes development of β-titanium alloys powders designed for application in additive manufacturing technologies. TiNbZrTa (TNZT)-based 3D structures were successfully manufactured and mechanically tested.
Influence of Constant Magnetic Fields on Defect Formation under Conditions of Heat Shock in Surface Layers of Silicon
Authors: Skvortsov Arkady A. , Pshonkin Danila E. , Luk'yanov Mikhail N.
Published: June 2018

The work is devoted to the study of defect formation processes in the near-surface layers of silicon under thermal shock conditions and to the effect of preliminary exposure in a constant magnetic field on this process. As a result of investigations it was established that dislocation half-loops near the local heat source are formed in the near-surface layers of Si (with a depth of up to 30 μm) after a current pulse of density j> 5.1010 A / m2 passing through the metallized film on the silicon surface. In addition, it was found that preliminary exposure of samples in a constant magnetic field leads to an increase in the dislocation density compared to samples not exposed in a magnetic field.
On the Parallel Implementation of BIM-Technologies in Construction and Operation of Buildings
Authors: Bai Vladimir , Maltsev Vladimir
Published: June 2018

The article reveals the main reasons for the failure of the schedule for implementing BIM-technologies in the construction industry in Russia. The state and level of use of BIM-technologies in various sectors of the construction industry is considered. The issue of implementing BIM-technologies in documentation of cadastral registration of capital construction objects is considered in more detail, since this issue has not been covered in the press yet. The integration of capital facilities and plots of land into a unified real estate register is declared, which is natural. But in view of the fact that land plots and capital facilities were previously accounted for in different registries by different departments, combining them into a unified register presents notable difficulties from the point of view of automating the production processes of creating, maintaining and storing registry documents. To determine the technical feasibility of combining two differently structured document registers, the macro-composition and data assignment in each of them were analyzed, common features and differences were revealed, and a method of combining documents of the same name from two registries into one was offered. A way to accelerate the implementation of BIM-technologies in the construction industry of Russia was offered. The possibility and necessity of parallel implementation of BIM-technologies in all sectors of the construction industry at the same time was justified.
Hydrophobic Modifiers for Restoration of Old Wooden Buildings in Western Siberia
Authors: Krutasov Boris V. , Ylesin Mikhail A. , Mashin Nikolay A. , Dubrov Dmitry V.
Published: June 2018

The paper deals with the issues of restoration of the wooden architecture monuments in Western Siberia by using the technology of wood modification. In order to modify the elements of the wooden buildings under restoration the authors studied hydrophobisators based on organic-silicone compounds. We have also defined the compositions and technologies of wood modification at the restoration of the wooden architecture monuments. Thermally modified wood may be used for restoration and replacement of the base courses of the wooden buildings.
Possibilities of New Information Technologies in the System of Urban Planning and Construction
Authors: Klyukin Aleksei A. , Kulachkovsky Valerii N. , Evseev Valerii N. , Klyukina Anna I.
Published: June 2018

The management quality of the process of territorial and urban planning and construction significantly affects the prospects for successful development of the city. A common problem in this case is objectively conditioned opposition of interests of municipal administrations, developers, designers and townspeople. Among the whole complex of problems generated by such confrontation in this paper, the problem of information support of urban development is highlighted. The main requirements are formulated, which should be met by information systems accompanying the urban development, and it is also shown that the present existing and traditional architecture does not fully meet the requirements for the majority of information systems such as "data storage – information consumer". A new approach to the construction of information systems for the provision of city planning activity based on the recently emerged protocols of interaction in the information field and information technologies is proposed. It is shown that the optimal solution of the problem can be found in a bundle of technologies of the mediated interaction "supplier-receiver" of the Uber type, blockchain and smart contracts on the blocking platform. The place and boundaries of applicability of each of these protocols are determined and the possible results of the joint work of these technologies in the sphere of town planning are shown.
The Effect of Support Pretreatment with Ammonia on Pd/SiO2 Catalyst
Authors: Kwon Ji Soo , Baek Jae Ho , Lee Hak Sung , Lee Man Sig
Published: June 2018

We have reported the effect of support pretreatment with ammonia on Pd/SiO2 catalyst in this study. SiO2 was pretreated with ammonia water to increase the Pd dispersion before the preparation of Pd/SiO2 catalysts. The effect of support pretreatment with ammonia on Pd/SiO2 catalyst was investigated by XRD, FT-IR, N2-adsorption and FE-TEM. The Pd supported on pretreated SiO2 were characterized by XRD, CO-chemisorption and FE-TEM. The pretreatment of SiO2 with ammonia water lead to decrease of silanol groups (Si-OH) up to temperature 200 °C. This decline of silanol groups on the SiO2 affects highly dispersed Pd/SiO2 as 6.52 %. The result showed that the decrease of silanol group on the SiO2 was favorable for the Pd dispersion. It is reason that absence of the silanol groups contribute to the high metal reducibility.
Influence of the Morphology of Alumina Filler on Electrical and Thermal Properties of Epoxy Resin Composites
Authors: Ma Jia Wei , Gao Nai Kui , Ren Teng Yue , Pan Ze Hua , Jin Hai Yun
Published: June 2018

Epoxy resin composites filled with alumina (Al2O3) particles of different morphology and content were fabricated by vacuum casting method. Electric and thermal properties of the composites were tested at room temperature to investigate the influence of Al2O3 morphology on epoxy resin composites. Electrical tests demonstrated that, volume resistivity of epoxy resin composites filled with spherical Al2O3 was bigger than with spherical-like Al2O3, relative permittivity and dielectric loss of epoxy resin composites increased with increasing of Al2O3 content, the effect on dielectric properties of spherical-like Al2O3, which had larger specific surface areas, was larger than spherical Al2O3 for the same content of filler. Thermal conductivity tests proved that, at the same content, thermal conductivity of epoxy resin composites filled with spherical-like Al2O3 was higher than with spherical Al2O3. According to the Agari model, spherical-like Al2O3 particles were easier to form conducting pathways in epoxy resin composites than spherical Al2O3 particles, considering their matte edges.
Relationship between Deep Donors and Current-Voltage Properties in Au/CdZnTe/Au Device
Authors: Zhang Yu Qian , Fu Li
Published: June 2018

Comprehending the current-voltage properties of CdZnTe device is an essential step toward improving its spectroscopic performance. Thus an in-depth analysis of I-V characteristics on Au/Cd0.9Zn0.1Te/Au device is carried out in this work. Typical non-linear transitions observed in I-V curve are found to be closely correlated with deep donor in CdZnTe. Profile of deep donor ionization probability is calculated under various biases. Afterwards the distribution of space charge and electric field is obtained. Based on these results, reasons for transitions in I-V curve are revealed. Also, related carrier transport mechanisms are confirmed.
Preparation of Siliconized Graphite by Liquid Silicon Infiltration of Porous Carbon Materials
Authors: Zhao Ying Ying , Wang Wei Min , Xia Hong Yan , Wang Ji Ping
Published: June 2018

Siliconized graphite was prepared by liquid silicon infiltration (LSI) of carbon preforms composed of mesocarbon microbeads (MCMBs), petroleum coke and graphite powder as the carbon source with binder of phenolic resin. Effects of the carbon source, binder contents, ball-milling time and moulding pressure on the properties of the porous carbon preforms and the siliconized graphite were investigated. The results showed that the moulding pressure was the main factor influencing the open porosity of the carbon preforms. The carbon preforms with porosity of above 45% could be infiltrated completely with Si, and maximum open porosity of 56% could be reached for the carbon preforms. For the siliconized graphite, high MCMBs contents contributed to high density, while high graphite content led to increased carbon remaining. The densities, open porosities, and the highest bending strength of the siliconized graphite were ranged between 2.90-3.01g·cm-3, less than 1.5%, and 317 MPa, respectively.
Effect of AlF3 Content on Microstructure and Properties of Mullite/Al2O3 Composite Ceramics
Authors: Sang Ke Zheng , Wang Fan , Zeng De Jun , Li Hong Wei
Published: June 2018

To reinforce the mullite/Al2O3 composite ceramics through formation of mullite whiskers, the composite ceramics were prepared by pressureless sintering using different AlF3 content. The microstructure, porosity, fracture toughness and thermal shock resistance of the composite ceramics were investigated. The results show that the addition of AlF3 can promote the mullite whisker formations, and the whiskers with the size of 3～10μm in diameter and a length-diameter ratio of 10～15 are obtained by sintering at 1600°C with the AlF3 content of 5wt%. Fracture toughness and thermal shock resistance of the composite ceramics are improved by the formation of mullite whisker. The fracture toughness of 4.79MPa•m1/2 can be obtained, and the 95.18% flexural strength remained after thermal shock.
Solvothermal Synthesis of TiO2-Modified Hydroxyapatite Using Water-Isopropanol Solution
Authors: Goto Tomoyo , Cho Sung Hun , Ohtsuki Chikara , Sekino Tohru
Published: June 2018

We synthesized TiO2 nanoparticles dispersed hydroxyapatite (TiO2-modifed HAp) by solvothermal treatment of α-tricalcium phosphate (α-TCP) using water-isopropanol solution including tetraisopropyl orthotitanate (TTIP). Rod-shaped HAp with TiO2 nanoparticles were formed by solvothermal treatment. HAp formation decreased with increasing the isopropanol fraction in the solution with TTIP. With increasing the treatment period, the rate of HAp formation in sample increased. The aspect ratio of HAp decreased with increasing the isopropanol fraction in the solution. Synthesized TiO2-modifed HAp samples shows the photocatalytic decoloration of methylene blue under UV irradiation.
Synthesis of Silicon Nitride Ceramic Fibers and the Effect of Nitrogen Atmosphere on their Morphology
Authors: Baba Sotaro , Goto Tomoyo , Cho Sung Hun , Sekino Tohru
Published: June 2018

The effect of nitrogen gas flow rate on the morphology of silicon nitride fibers obtained via carbothermal nitridation heat treatment method was investigated. A precursor containing silicon, oxygen and carbon was obtained by a sol-gel method from a mixture of tetraethyl orthosilicate, polyvinyl alcohol, H2O and ethanol. A white wool-like product was obtained by heat treating the precursor placed in an alumina crucible under a 0.5 MPa nitrogen gas pressure at 1500oC with different nitrogen gas flow rates. The mass-based production rates of the samples obtained from the precursor powder were 20-30% for the different nitrogen gas flow rates. X-ray diffraction analysis revealed that the samples contained α-Si3N4 as the major phase along with β-Si3N4, Si2N2O and a small amount of amorphous product as minor phases. Unique twisted fibers with diameters of several hundreds of nanometers were found among the straight fibers by SEM observation. Elemental analysis using energy dispersive X-ray spectroscopy indicated that silicon and nitrogen were contained in the twisted fibers along with approximately 68 at.% of oxygen and several at.% of aluminum, which might have come from the crucible material. The SiAlON-like structures might have been formed by the partial dissolution of Al and O in the Si3N4 fibers. It was considered that the twisted morphology of some fibers might be formed by co-existing of β-SiAlON and/or amorphous phase regions in the Si3N4 fiber and resultant distortion of the fibers.
Fire Condition Effects on the Mechanical Behaviour of Composite Structures
Authors: Saputo Salvatore , Russo Angela , Raimondo Antonio , Iodice Barbara , Zarrelli Mauro
Published: June 2018

The fire behaviour of Polymeric composite structures is one of the most critical aerospace research topics. Indeed, the exposure of Polymeric composite structures to high temperatures leads to material decomposition, associated to thermal and mechanical properties degradation. This degradation causes a reduction of the mechanical performances, which can be of main concern for safety reasons. In this paper, the tensile behaviour of Carbon Fibre Composite Polymer specimens, subjected to fire, has been experimentally and numerically investigated. The material properties degradation has been estimated according to an Arrhenius shape function, which relates the mechanical properties of the composite to the temperature. At first, static structural analyses have been carried out to assess the mechanical behaviour of the investigated specimen without fire effects. Then, a coupled thermo-structural analysis allowed evaluating the fire effect on the specimens’ mechanical and the thermal behaviour. In order to preliminary validate the proposed degradation model, the numerical results, in terms of Load versus Displacements curves, have been compared against data obtained from an ad-hoc experimental campaign where fire condition have been suitably replicated during the mechanical tests.
Life Cycle Assessment on the Effects of Parameter Setting in Direct Recycling Hot Press Forging of Aluminum
Authors: Lajis Mohd Amri , Yusuf Nur Kamilah , Ahmad Azlan
Published: June 2018

Metallic material processing plays a significant role in terms of global environmental impact which contributes to the climate change phenomena that is a serious international environmental concern and the subject of much research and debate. Thus, energy-and resource-efficient strategies in the metal shaping technology domain need to be identified urgently. A frequent theme in the debates that surround waste and resources management is the extent to which the recycling of metallic materials offers genuine benefits to the environment. Solid state recycling techniques allow the manufacture of high density aluminum alloy parts directly from production scrap. In this paper the environmental impacts associated with ‘meltless’ scrap processing routes through hot press forging process with varying parameter has been studied. A comparative analysis has been performed, with different operating temperature and holding time of direct recycling hot press forging process AA6061 aluminum chip. The importance of an environmental performance analysis that included both parameter setting was discussed and highlighted throughout the paper. Finally, the application of the proposed parameter setup has resulted in the setting up of an eco-process. Indeed, LCA study on recycling (solid-state) are recommended as well it gives a noteworthy benefit to the environment and to fill the knowledge gap.
An Alteration of the Time-Temperature Superposition Principle to Account for Environmental Degradation in Fibre Reinforced Plastics
Authors: Ngoy Etienne Kolomoni
Published: June 2018

The approach suggested in this analysis stems from basic material science laws and considers that any environmental degradation of polymer composites ultimately consists in chemical link and cohesion force alteration. Such alteration leads to the modification of material viscoelastic characteristics that can be measured through stress relaxation or creep. Then the analysis deals with the applicability of the time-temperature shift principle for prediction test in cases involving environmental degradation. It is demonstrated that the shift factor as determined from Arrhenius Law needs to incorporate an additional term to account for the variation of the activation energy of the chemical and physical degradation. The method leads to excellent prediction of the time and environment dependent material strength.
Change in Crystalline Structure of Cellulose Caused by Wood Preservation
Authors: Stepina Irina Vasilevna
Published: June 2018

Сhemical interaction of cellulose with reactive groups of four-coordinate boron-nitrogen compounds is an intercrystalline process proceeding without destruction of cellulose crystalline structure; probably, the modifier molecules react with easier accessible hydroxyl groups of the amorphous cellulose regions. The formation of B-O-C ether bonds between OH groups of modifiers and more reactive hydroxyl groups of amorphous parts of cellulose results in redistribution of hydrogen bonds and, as a consequence, to rectification of cellulose macromolecules. Thus, when cellulose is treated with compositions based on four-coordinate boron-nitrogen compounds, crystalline structure of cellulose is not disrupted, hence this process can be called a "mild" modification. Such modification does not lead to accelerated aging of cellulose materials, rapid loss of strength and increases durability of wooden structures.
Influence and Mutual Interaction of Process Parameters on the Z1/2 Defect Concentration during Epitaxy of 4H-SiC
Authors: Erlekampf Jürgen , Kaminzky Daniel , Rosshirt Katharina , Kallinger Birgit , Rommel Mathias , Berwian Patrick , Friedrich Jochen , Frey Lothar
Published: June 2018

The development of bipolar 4H-SiC devices for high blocking voltages requires the growth of high carrier lifetime epitaxial layers with low Z1/2 concentrations. This paper shows a comprehensive investigation of the influence of epitaxial growth parameters (C/Si ratio and growth temperature) on Z1/2 concentration and minority carrier lifetime. On the basis of a discovered exponential correlation of Z1/2 with the C/Si ratio and growth temperature, a competitive low Z1/2 concentration of 1.9∙1012 cm-3 could be achieved by lowering the growth temperature and switching to higher C/Si ratio. Thermodynamic considerations by an Arrhenius approach reveal a dependency of the formation enthalpy of Z1/2 on the thermal process and process conditions of the epitaxial growth. Furthermore, the correlation between Z1/2 and the effective minority carrier lifetime confirms the occurrence of a necessary second recombination mechanism beside the common recombination at deep levels by Shockley-Read-Hall for low Z1/2 concentration.
Stacking Faults Defects on 3C-SiC Homo-Epitaxial Films
Authors: Litrico Grazia , Anzalone Ruggero , Alberti Alessandra , Bongiorno Corrado , Nicotra Giuseppe , Zimbone Massimo , Mauceri Marco , Coffa Salvo , La Via Francesco
Published: June 2018

Stacking Faults (SFs) are the main defect of 3C-SiC material and in this work a detailed study of this typology of defect is presented. We studied the behavior of SFs with High Resolution XRD and STEM analysis. The homo-epitaxial growth was proposed as a solution for the reduction of SFs density in 3C-SiC material and the influence of the growth condition on the SFs density was studied. The knowledge of the mechanism of SFs reduction is crucial for the development of a high quality material for devices fabrication.
Structural Characterization of the Growth Front of 4H-SiC Boules Grown Using the Physical Vapor Transport Growth Method
Authors: Sonoda Masashi , Shioura Kentaro , Nakano Takahiro , Ohtani Noboru , Katsuno Masakazu , Tsuge Hiroshi , Sato Shinya , Fujimoto Tatsuo
Published: June 2018

The defect structure at the growth front of 4H-SiC boules grown using the physical vapor transport (PVT) method has been investigated using high resolution x-ray diffraction and x-ray topography. The crystal parameters such as the c-lattice constant exhibited characteristic variations across the growth front, which appeared to be caused by variation in surface morphology of the as-grown surface of the boules rather than the defect structure underneath the surface. X-ray topography also revealed that basal plane dislocations are hardly nucleated at the growth front during PVT growth of 4H-SiC crystals.
Expansion of Basal Plane Dislocation in 4H-SiC Epitaxial Layer on A-Plane by Electron Beam Irradiation
Authors: Sudo Masaki , Ishikawa Yukari , Yao Yong Zhao , Sugawara Yoshihiro , Kato Masashi
Published: June 2018

The expansion behavior of basal plane dislocations (BPDs) in a 4H-SiC epitaxial layer on the (110) A-plane under electron beam (EB) (//[110]) irradiation was observed. BPD expanded and formed a single Shockley stacking fault (SSSF) between a partial dislocation (PD) pair. The width of the SSSF was proportional to the EB current. The dependence of the expansion velocity on the irradiation position was observed with a fixed EB spot. It was found that the electron-hole pair migration to the PD and/or SSSF can expand the SSSF. The velocity of SSSF expansion by direct SSSF excitation with an EB was much smaller than that by the preferential excitation of a PD with migrated electron-hole pairs.
Optical Stressing of 4H-SiC Material and Devices
Authors: Kallinger Birgit , Kaminzky Daniel , Berwian Patrick , Friedrich Jochen , Oppel Steffen
Published: June 2018

Electrical testing with regard to bipolar degradation of high voltage SiC devices cannot be done on wafer level, but only expensively after module assembly. We show that 4H-SiC material can be optically stressed by applying high UV laser intensities, i.e. bipolar degradation as in electrical stress tests can be provoked on wafer level. Therefore, optical stressing can be used for control measurements and reliability testing. Different injection (=stress) levels have been used similar to the typical doping level of the base material and similar to the established electrical stress test. The analysis of degradation is done by photoluminescence imaging which is a well-established technique for revealing structural defects such as Basal Plane Dislocations (BPDs) and stacking faults (SFs) in 4H-SiC epiwafers and partially processed devices.
Optical and Microstructural Investigation of Heavy B-Doping Effects in Sublimation-Grown 3C-SiC
Authors: Galeckas Augustinas , Carvalho Patricia Almeida , Ma Quan Bao , Azarov Alexander , Hovden Sigurd , Thøgersen Annett , Wright Daniel N. , Diplas Spyros , Løvvik Ole Martin , Jokubavicius Valdas , Sun Jian Wu , Syväjärvi Mikael , Svensson Bengt Gunnar
Published: June 2018

In this work, a complementary microstructural and optical approach is used to define processing conditions favorable for the formation of deep boron-related acceptor centers that may provide a pathway for achieving an intermediate band behavior in highly B-doped 3C-SiC. The crystallinity, boron solubility and precipitation mechanisms in sublimation-grown 3C-SiC crystals implanted to 1-3 at.% B concentrations were investigated by STEM. The revealed defect formation and boron precipitation trends upon thermal treatment in the range 1100-2000°C have been cross-correlated with the optical characterization results provided by imaging PL spectroscopy. We discuss optical activity of the implanted B ions in terms of both shallow acceptors and deep D-centers, a complex formed by a boron atom and a carbon vacancy, and associate the observed spectral developments upon annealing with the strong temperature dependence of the D-center formation efficiency, which is further enhanced by the presence of implantation-induced defects.
Rearrangement of Surface Structure of 4o Off-Axis 4H-SiC (0001) Epitaxial Wafer by High Temperature Annealing in Si/Ar Ambient
Authors: Ashida Koji , Dojima Daichi , Torimi Satoshi , Yabuki Norihito , Sudo Yusuke , Sakaguchi Takuya , Nogami Satoru , Kitabatake Makoto , Kaneko Tadaaki
Published: June 2018

Mechanism of surface roughening caused by the polishing induced subsurface damage on 4o off-cut 4H-SiC (0001) substrate during thermal etching, CVD epitaxial growth, and the subsequent high temperature annealing was investigated in the wide temperature range of 1000-1800°C. Different from the previous study based on a macroscopic characterization by optical microscopy, microscopic characterization based on a scanning electron microscopy (SEM) was employed in this study. By utilizing the SEM operated under various conditions, disordered step arrangements as well as stacking faults and dislocations were imaged. The obtained results revealed that the SFs cause the fluctuation in the step kinetics, resulting in the step bunching formation during the thermal process.
Determination of Performance-Relevant Trapped Charge in 4H Silicon Carbide MOSFETs
Authors: Rasinger Fabian , Pobegen Gregor , Aichinger Thomas , Weber Heiko B. , Krieger Michael
Published: June 2018

Current-voltage characterization and thermal dielectric relaxation current (TDRC) measurements are carried out on 4H silicon carbide (SiC) n-channel MOSFETs processed with different post oxidation anneals (POAs) in O2, N2O, and NO atmospheres at high temperature. In all samples we observe a distinct peak at a temperature of 70 K in the TDRC spectra due to a defect close to the conduction band of 4H-SiC having a high density of states (>1013 cm-2eV-1). We show that this defect is related to the degradation of the device performance such as the MOSFET conductivity. Comparing the different POAs, NO strongly reduces the density of states close to the conduction band and thus increases the amount of free channel electrons. Based on TDRC measurements we want to suggest a method for more accurate estimation of the true channel mobility accounting for the reduced channel electron density due to trapping.
Simulations of Heterostructures Based on 3C-4H and 6H-4H Silicon Carbide Polytypes
Authors: Rashid Muhammad Haroon , Koel Ants , Rang Toomas
Published: June 2018

In the last decade, silicon carbide (SiC) has gained a remarkable position among wide bandgap semiconductors due to its high temperature, high frequency, and high power electronics applications. SiC heterostructures, based on the most prominent polytypes like 3C-SiC, 4H-SiC and 6H-SiC, exhibit distinctive electrical and physical properties that make them promising candidates for high performance optoelectronic applications. The results of simulations of nn-junction 3C-4H/SiC and 6H-4H/SiC heterostructures, at the nanoscale and microscale, are presented in this paper. Nanoscale devices are simulated with QuantumWise Atomistix Toolkit (ATK) software, and microscale devices are simulated with Silvaco TCAD software. Current-voltage (IV) characteristics of nanoscale and microscale simulated devices are compared and discussed. The effects of non-ideal bonding at the heterojunction interface due to lattice misplacements (axial displacement of bonded wafers) are studied using the ATK simulator. These simulations lay the groundwork for the experiments, which are targeted to produce either a photovoltaic device or a light-emitting diode (working in the ultraviolet or terahertz spectra), by direct bonding of SiC polytypes.
Influence of Aluminum Incorporation on Mechanical Properties of 3C-SiC Epilayers
Authors: Michaud Jean François , Zielinski Marcin , Messaoud Jaweb Ben , Chassagne Thierry , Portail Marc , Alquier Daniel
Published: June 2018

The silicon carbide cubic polytype (3C-SiC) is perfectly appropriate to fabricate microelectromechanical systems. However, for such applications, the stress can largely influence both the fabrication of 3C‑SiC‑based microsystems and their related mechanical properties. Accordingly, in this study, we investigated the influence of strong aluminum incorporation towards the mechanical properties of 3C-SiC epilayers grown on silicon substrates.
Double Step Annealing for the Recovering of Ion Implantation Defectiveness in 4H-SiC DIMOSFET
Authors: Zimbone Massimo , Piluso Nicolo , Litrico Grazia , Nipoti Roberta , Reitano Riccardo , Canino Mariaconcetta , di Stefano Maria Ausilia , Lorenti Simona , La Via Francesco
Published: June 2018

Thermal annealing plays a crucial role for healing the defectiveness in the ion implanted regions of DIMOSFETs (Double Implanted MOSFETs) devices. In this work, we have studied the effect of a double step annealing on the body (Al implanted) and the source (P implanted) regions of such devices. We found that a high temperature annealing (1750°C, 1h) followed by a lower temperature one (1500°C, 4h) is mandatory to achieve low defects concentration and good crystal quality in both the n-and p-type zones of the device.
Influence of Al Doping Concentration and Annealing Parameters on TiAl Based Ohmic Contacts on 4H-SiC
Authors: Kocher Matthias , Rommel Mathias , Erlbacher Tobias , Bauer Anton J.
Published: June 2018

TLM structures on Al-implanted regions with different implanted Al concentrations and different annealing temperatures were processed and characterized by electrical measurements in order to determine the influence of these parameters on the ohmic resistivity. Based on these results, a TCAD model was developed that considers the carrier concentration of the implanted region, the effective density of states for holes and the hole tunneling mass at the Ti3SiC2-SiC interface. It could be shown that Ti3SiC2 allows to form ohmic contacts on Al implanted samples with an effective doping concentration down to 3·1017 cm-3. Furthermore the effective density of states for holes in Ti3SiC2 was determined to 8.5·1018 cm-3 and the hole tunneling mass in SiC and Ti3SiC2 in the range of 2·10-34 kg to 6·10-33 kg depending on the sample.
Low Resistance Ti5Si3/TiC Ohmic contact on Ion-Implanted n-Type 4H-SiC C Face
Authors: De Silva Wijemuni , Kawasaki Teruhisa , Kuroki Shin Ichiro
Published: June 2018

Low-resistance Ohmic contact on n+ 4H-SiC C-face with Titanium was demonstrated. In a conventional NiSi Ohmic contat on n-type 4H-SiC, a carbon agglomeration at the silicide/SiC interface occurs, and contact resistance becomes larger. For suppressing the carbon agglomeration, laser annealing and Ti metal were introduced to form both silicide and carbide. Ti (75 nm)/SiC and Ni (75 nm)/SiC Ohmic contacts were formed on backside C-face of high concentration impurity doped 4H-SiC substrates with and without activation annealing. Electrical properties were investigated after 40 nanoseconds pulse laser annealing in Ar ambient. As the result, the lowest specific contact resistance of 7.9×10-5 Ωcm2 was obtained in Ti (75 nm)/SiC sample in the case of ion implanted sample at 500°C and with activation annealing at a laser power of 2.2 J/cm2.
Study on NO Passivation on the Near Interface Electron and Hole Traps of n-Type 4H-SiC MOS Capacitors by Ultraviolet Light
Authors: Jia Yi Fan , Lv Hong Liang , Tang Xiao Yan , Song Qing Wen , Zhang Yi Men , Zhang Yu Ming
Published: June 2018

The characteristics of near interface electron and hole traps in n-type 4H-SiC MOS capacitors with and without nitric oxide (NO) passivation have been systematically investigated. The hysteresis of the bidirectional capacitance-voltage (C-V) and the shift of flat band voltage (Vfb) caused by bias stress (BS) with and without ultraviolet light (UVL) irradiation are used for studying the influence of near interface electron traps (NIETs) and near interface hole traps (NIHTs). Compared with Ar annealed process, NO passivation can effectively reduce the density of NIETs, but induce excess NIHTs in the SiC MOS devices. What’s worse is that part of the trapped hole cannot be released easily from the NIHTs in the NO annealed sample, which may act as the positive fixed charge and induce the negative shift of threshold voltage.
Modification of Crucible Shape in Top Seeded Solution Growth of SiC Crystal
Authors: Kim Young Gon , Choi Su Hun , Shin Yun Ji , Jeong Seong Min , Lee Myung Hyun , Lee Chae Young , Choi Jeong Min , Park Mi Seon , Jang Yeon Suk , Lee Won Jae
Published: June 2018

The modified crucible in the top seeded solution growth (TSSG) method was proposed to get the stable growth condition and the enhanced growth rate. The temperature gradient and the distribution of dissolved carbon in the solvent were obtained by numerical approaches. Compared simulation results and experiment, we investigated the region where is the most of dissolved carbon and it is supplied to the seed through what path. The cross-sectional samples of crucibles and grown SiC crystals were systematically analyzed to investigate the effect of the crucible modification on SiC crystal growth.
Automated Mapping of Micropipes in SiC Wafers Using Polarized-Light Microscope
Authors: McGuire Sean , Blasi Robert , Wu Ping , Loukas Efstathios , Emorhokpor Ejiro , Dimov Svetoslav , Xu Xue Ping , Guo Jian Qiu , Yang Yu , Raghothamachar Balaji , Dudley Michael
Published: June 2018

We have developed a process that is able to detect, count, and map micropipes on SiC substrates. This process uses a polarized light microscope to scan the wafer. The pictures taken are analyzed with a program that produces a micropipe map as well as numerical defect distribution data in a text file. The results of the process were validated with x-ray topography measurement. The repeatability of this process is also studied and reported.
Effects of Parasitic Region in SiC Bipolar Junction Transistors on Forced Current Gain
Authors: Asada Satoshi , Suda Jun , Kimoto Tsunenobu
Published: June 2018

Effects of a parasitic region in SiC BJTs on conductivity modulation and a forced current gain (βF) were investigated by using TCAD simulation with various device structures. By introducing an Al+-implanted region below the base parasitic region, βF can be improved because the implanted region can reduce the base spreading resistance, leading to alleviation of debiasing effect. βF in devices with various parasitic areas, whose base spreading resistances were reduced by the Al+-implantation, were compared. We found that βF can be enhanced by expanding the parasitic area if the base spreading resistance is sufficiently reduced. The higher βF is attributed to an expanded conductivity-modulated region. The collector current spreading in the collector layer and the hole injection from the parasitic region as well as from the intrinsic region can play a role to evoke the conductivity modulation. Thus, the larger parasitic region can expand the conductivity-modulated region, resulting in expansion of an active area and the enhancement of βF.
TCAD Modeling of a 1200 V SiC MOSFET
Authors: Lee Kwang Won , Buono Benedetto , Domeij Martin , Franchi Jimmy
Published: June 2018

In this work, TCAD modeling of a 1200 V SiC MOSFET is presented. The main focus is on modeling of the channel mobility, and the Coulomb scattering by interface traps and surface roughness are therefore included. For the Coulomb scattering, the interface trap profiles have been extrapolated from the subthreshold characteristics at room temperature, whereas the scattering due to surface roughness has been fitted by comparing to the transfer characteristics at high gate bias. A comparison with measurements for the transfer characteristic and the output characteristic is also presented. Results show that the reduction of the threshold voltage with increasing temperature and the temperature dependence of the output characteristics are properly modeled.
4600 V Sic Dmosfets with RDS,On = 17 mΩ-cm2
Authors: Sundaresan Siddarth G. , Jeliazkov Stoyan , Singh Ranbir
Published: June 2018

Large-area, 7.84 mm2 SiC DMOSFETs feature breakdown voltages of 4600 V, specific on-resistance of 17 mΩ-cm2 and gate threshold voltage of 2.4 V. The low on-resistance was enabled by an optimized MOS process that resulted in channel mobility as high as 27 cm2/Vs, and oxide breakdown fields in the 10-11 MV/cm range. The key device design and layout parameters were varied to examine the performance versus reliability trade-offs.
Role of Trench Bottom Shielding Region on Switching Characteristics of 4H-SiC Double-Trench Mosfets
Authors: Kyogoku Shinya , Tanaka Katsuhisa , Ariyoshi Keiko , Iijima Ryosuke , Kobayashi Yusuke , Harada Shinsuke
Published: June 2018

The effect of a gate trench bottom p+ region (BPR) on the dynamic characteristics of 4H-SiC double-trench MOSFETs was investigated. Although employing a BPR led to an improved trade-off in the static characteristics, a BPR adversely affected the switching characteristics in spite of a reduction in the Miller capacitance compared to the case without a BPR. Simulation analysis revealed that a resistance between a BPR and a source electrode led to an increase in the switching loss. We have found reduction of the resistance is insufficient in order to provide benefits from the BPR. Hence, it is necessary to improve layouts of contacts of the BPR to the source electrode.
Impact of Cell Geometry on Zero-Energy Turn-Off of SiC Power MOSFETs
Authors: Liu Xueqing , Chowdhury Sauvik , Hitchcock Collin W. , Chow T. Paul
Published: June 2018

1200V SiC power MOSFETs of various cell geometries are modeled in Synopsis Inc. Sentaurus TCAD. The impact of cell geometry on switching loss is studied by comparing the turn-on and turn-off losses using refined calculation methods. Under optimum circuit conditions, two different novel unit cell designs each achieve lower switching losses than conventional designs. For all the designs, lossless turn-on is impossible but lossless turn-off is achievable under circuit and biasing conditions that produce sufficiently rapid gate slew.
First Demonstration of High Temperature SiC CMOS Gate Driver in Bridge Leg for Hybrid Power Module Application
Authors: Weng Ming Hung , Idris Muhammad I. , Wright S. , Clark David T. , Young R.A.R. , McIntosh J.R. , Gordon D.L. , Horsfall Alton B.
Published: June 2018

A high-temperature silicon carbide power module using CMOS gate drive technology and discrete power devices is presented. The power module was aged at 200V and 300 °C for 3,000 hours in a long-term reliability test. After the initial increase, the variation in the rise time of the module is 27% (49.63ns@1,000h compared to 63.1ns@3,000h), whilst the fall time increases by 54.3% (62.92ns@1,000h compared to 97.1ns@3,000h). The unique assembly enables the integrated circuits of CMOS logic with passive circuit elements capable of operation at temperatures of 300°C and beyond.
Short-Circuit Capability of SiC Cascode
Authors: Li Xue Qing , Bhalla Anup , Alexandrov Peter
Published: June 2018

This work investigates the short-circuit capability of SiC cascode by performing two-dimensional electro-thermal TCAD simulations. The effects of the threshold voltage of the SiC JFET on the cascode short-circuit withstand time are studied. A design trade-off between the JFET specific-on resistance and the cascode short-circuit withstand time is determined. The experimental results are also presented.
Benefits of High Voltage SiC Applications in Medium Voltage Power Distribution Grids
Authors: Ji Shi Qi , Shi Xiao Jie , Zhang Zhe Yu , Cao Wen Chao , Wang Fred
Published: June 2018

This paper evaluates potential benefits of high voltage (HV) SiC devices in medium voltage (MV) distribution grids. The MV microgrid, that HV SiC devices can benefit most, is selected as the “killer application” and focused in this paper. The design and simulation are carried out to compare Si-and SiC-based grid interface converters for the quantitative benefit assessment both at converter level and system level. The SiC-based converter has significant benefits in weight and size, and shows enhanced performance and functionality on power quality, system stability and low voltage ride through (LVRT) as well.
Module and System Considerations to Maximize Performance Advantages of SiC Power Devices
Authors: McNutt Ty , Olejniczak Kraig , Minden Stephen , Martin Daniel , Hayes Jonathan , Wijenayake Ajith , Simco David
Published: June 2018

This paper extends a previously presented SiC power module design philosophy to critical, higher-level components for increased system performance, namely the DC bussing and DC link capacitor design. The DC bussing is essential to connect the DC bulk capacitors to the high-speed power modules and it is imperative that low inductance is maintained while current carrying capability and temperature be maintained. Often, high frequency capacitors are added to systems to increase performance by compensating for extra stray inductance that the DC bussing can introduce. However, issues that may arise by doing such are presented and it is shown that the best solution is to optimize the DC bus structure rather than compensate for a poor design. Finally, the implemented bussing is shown and full power system results presented for the inverter stack-up design.
Processing of Cavities in SiC Material for Quantum Technologies
Authors: Myers-Ward Rachael L. , Hobart Karl D. , Daniels Kevin M. , Giles Alex J. , Tadjer Marko J. , Luna Lunet E. , Kub Francis J. , Pavunny Shojan P. , Carter Sam G. , Banks Hunter B. , Glaser Evan R. , Klein Paul B. , Feygelson Boris N. , Gaskill D. Kurt
Published: June 2018

Quantum technology is a field of significant interest that will benefit many applications including communications and sensing. SiC is a promising material for quantum applications such as quantum memories, due to point defects, specifically VSi, in the material, which result in long spin coherence times. We have found that no VSi are present in our epitaxially grown unintentionally and nitrogen-doped 4H-SiC with electron concentrations ranging from 1014 to 1018 cm-3. We create these vacancies using electron irradiation, in concentrations from single defects to ensembles. To utilize the defect luminescence for realistic applications, we have fabricated the SiC into photonic crystal arrays. We present the processing steps required to create photonic crystal cavities in SiC and subsequent challenges.
Electric Field Characterization of Diamond Metal Semiconductor Field Effect Transistors Using Electron Beam Induced Current
Authors: Driche Khaled , Umezawa Hitoshi , Ohmagari Shinya , Okumura Hajime , Mokuno Yoshiaki , Gheeraert Etienne
Published: June 2018

Lateral gate depletion expansion towards drain contact has been analyzed on p-type diamond metal-semiconductor field effect transistor by electron beam induced current. The investigation was restricted to a closed channel to simplify the study and to directly observe the expansion of the lateral depletion region. The experimental data agreed with the theoretical model given in the literature.
Quick and Practical Cleaning Process for Silicon Carbide Epitaxial Reactor
Authors: Shioda Kohei , Kurashima Keisuke , Habuka Hitoshi , Ito Hideki , Mitani Shinichi , Takahashi Yoshinao
Published: June 2018

In order to develop a quick and practical cleaning process for the silicon carbide chemical vapor deposition reactor, the pyrolytic carbon-coated susceptor was used. The 30-μm-thick silicon carbide film was formed on the susceptor; the film was cleaning by chlorine trifluoride gas at 460 °C for 15 min. The remained fluorine was removed by the annealing at 900 °C in ambient hydrogen. The pyrolytic carbon surface did not suffer from any damage, because the pyrolytic carbon film surface morphology after the cleaning process was the same as that before the silicon carbide film deposition.