Showing papers on "Silicon carbide published in 2018"

High thermal conductivity in cubic boron arsenide crystals.

Abstract: The high density of heat generated in power electronics and optoelectronic devices is a critical bottleneck in their application. New materials with high thermal conductivity are needed to effectively dissipate heat and thereby enable enhanced performance of power controls, solid-state lighting, communication, and security systems. We report the experimental discovery of high thermal conductivity at room temperature in cubic boron arsenide (BAs) grown through a modified chemical vapor transport technique. The thermal conductivity of BAs, 1000 ± 90 watts per meter per kelvin meter-kelvin, is higher than that of silicon carbide by a factor of 3 and is surpassed only by diamond and the basal-plane value of graphite. This work shows that BAs represents a class of ultrahigh-thermal conductivity materials predicted by a recent theory, and that it may constitute a useful thermal management material for high-power density electronic devices.

Ultralight, Recoverable, and High-Temperature-Resistant SiC Nanowire Aerogel.

Abstract: Ultralight ceramic aerogels with the property combination of recoverable compressibility and excellent high-temperature stability are attractive for use in harsh environments. However, conventional ceramic aerogels are usually constructed by oxide ceramic nanoparticles, and their practical applications have always been limited by the brittle nature of ceramics and volume shrinkage at high temperature. Silicon carbide (SiC) nanowire offers the integrated properties of elasticity and flexibility of one-dimensional (1D) nanomaterials and superior high-temperature thermal and chemical stability of SiC ceramics, which makes it a promising building block for compressible ceramic nanowire aerogels (NWAs). Here, we report the fabrication and properties of a highly porous three-dimensional (3D) SiC NWA assembled by a large number of interweaving 3C-SiC nanowires of 20–50 nm diameter and tens to hundreds of micrometers in length. The SiC NWA possesses ultralow density (∼5 mg cm–3), excellent mechanical properties o...

Probing spin-phonon interactions in silicon carbide with Gaussian acoustics

Abstract: Hybrid spin-mechanical systems provide a platform for integrating quantum registers and transducers. Efficient creation and control of such systems require a comprehensive understanding of the individual spin and mechanical components as well as their mutual interactions. Point defects in silicon carbide (SiC) offer long-lived, optically addressable spin registers in a wafer-scale material with low acoustic losses, making them natural candidates for integration with high quality factor mechanical resonators. Here, we show Gaussian focusing of a surface acoustic wave in SiC, characterized by a novel stroboscopic X-ray diffraction imaging technique, which delivers direct, strain amplitude information at nanoscale spatial resolution. Using ab initio calculations, we provide a more complete picture of spin-strain coupling for various defects in SiC with C3v symmetry. This reveals the importance of shear for future device engineering and enhanced spin-mechanical coupling. We demonstrate all-optical detection of acoustic paramagnetic resonance without microwave magnetic fields, relevant to sensing applications. Finally, we show mechanically driven Autler-Townes splittings and magnetically forbidden Rabi oscillations. These results offer a basis for full strain control of three-level spin systems.

Investigation of Mechanical Properties of Aluminium 6061-Silicon Carbide, Boron Carbide Metal Matrix Composite

Abstract: High demand on materials to increase the overall performance of automotive and aerospace components has forced the development of composite materials. Among the various composites, Aluminium Metal Matrix Composites (AMMC) are widely used to fulfill the emerging industrial needs. This paper deals with the investigation of mechanical properties of AMMC produced by the stir casting technique for various compositions of boron carbide and silicon carbide reinforced with aluminium alloy 6061. The tensile, flexural, hardness and impact tests were performed and it was found that the hybrid composites had better properties than pure aluminium. The microstructure of the hybrid composites was analysed using Scanning Electron Microscopy (SEM).

Aluminum Silicon Carbide Particulate Metal Matrix Composite Development Via Stir Casting Processing

Abstract: In this paper, conventional simple methods of producing MMC with attained properties through the dispersion of silicon carbide in the matrix are investigated To achieve these objectives a two-step mixing method of stir casting technique was employed Aluminum (9966 %CP) and SiC (320 and 1200 grits) were chosen as matrix and reinforcement materials respectively Experiments were conducted by varying the weight fraction of SiC for 25 %, 50 %, 75 % and 10 % The result indicated that the stir casting method was quite successful to obtain uniform dispersion of reinforcement in the matrix This was evident by the improvement of properties of composites over the base metal Reinforced Aluminum Silicon Carbide (ASC) showed an increase in Young’s modulus (E) and hardness above the unreinforced case and marginal reduction of electrical conductivity was recorded for the composites The silicon carbide of 1200 grits (3 μm) showed increased Young’s modulus (E) and hardness of 15176 Mpa and 261 Hv values at 75% volume fraction silicon carbide; when compared with the silicon carbide 320 grit (29 μm) Also; the electrical conductivity properties of the two grit sizes of the silicon carbides were less than the base metal for all the volume fractions of silicon carbide

A Megawatt-Scale Medium-Voltage High Efficiency High Power Density “SiC+Si” Hybrid Three-Level ANPC Inverter for Aircraft Hybrid-Electric Propulsion Systems

Abstract: Hybrid-electric propulsion system is an enabling technology to make the aircrafts more fuel-saving, quieter, and lower carbide emission. In this paper, a megawatt-scale power inverter based on a three-level active neutral-point-clamped (3L-ANPC) topology will be developed. To achieve high efficiency, the switching devices operating at carrier frequency in the power converter are configured by the emerging Silicon Carbide (SiC) Metal-Oxide Semiconductor Field-Effect Transistors (MOSFETs), while the conventional Silicon (Si) Insulated-Gate Bipolar Transistors (IGBTs) are selected for switches operating at the fundamental output frequency. To reduce system cable weight, the dc-bus voltage is increased to 2.4 kV. Unlike the conventional 400 Hz aircraft electric systems, the rated fundamental output frequency here is boosted to 1.4 kHz to drive the high-speed motor, which can also reduce system weight. Main hardware development and control modulation strategies are presented. Experimental results are presented to verify the performance of this MW-scale medium-voltage “SiC+Si” hybrid three-level ANPC inverter. It is shown that the 1-MW 3L-ANPC inverter can achieve a high efficiency of 99% and high power density of 12 kVA/kg.

3D-Printed Fe-doped silicon carbide monolithic catalysts for wet peroxide oxidation processes

Abstract: The catalyst stability has become a key issue for wet peroxide oxidation (CWPO) processes. Herein, an alternative method for the manufacturing of iron (Fe) catalysts by using three-dimensional (3D) printing techniques is proposed to enhance the Fe immobilization, where these metallic nanoparticles are part of a printable aqueous silicon carbide (SiC)-based ink. Cylindrical Fe/SiC monoliths (D ∼ 13 mm, H ∼ 4.5 mm, 74 squared cells cm−2) are manufactured by direct ink writing (Robocasting) and further treatment up to 1500 °C into a spark plasma sintering (SPS) furnace to assure a certain mechanical integrity. It was found that the increasing SPS temperature progressively decreases the porosity -or increases the apparent density- of the printed struts, lowering the accessibility of reactants to the Fe sites but improving the catalyst mechanical strength and leaching resistance. 3D Fe/SiC monoliths treated at 1200 °C arise as robust catalysts for CWPO processes due to the combination of good catalytic activity, highly- efficient H2O2 decomposition, long-term stability and excellent mechanical strength. A simple potential kinetic model is proposed, capable of describing the phenol disappearance, TOC removal and H2O2 consumption. The results of this study point out a new approach for the conformation by Robocasting of metal-based catalysts in suitable morphological 3D-structures for scaling-up reactions.

Single-Event Burnout of SiC Junction Barrier Schottky Diode High-Voltage Power Devices

Abstract: Ion-induced degradation and catastrophic failures in high-voltage SiC junction barrier Schottky power diodes are investigated. The experimental results agree with earlier data showing discrete jumps in leakage current for individual ions and show that the boundary between leakage current degradation and a single-event-burnout-like effect is a strong function of linear energy transfer and reverse bias. TCAD simulations show high localized electric fields under the Schottky junction, and high temperatures generated directly under the Schottky contact, consistent with the hypothesis that the ion energy causes eutectic-like intermixture at the metal–semiconductor interface or localized melting of the silicon carbide lattice.

Investigation of threshold voltage stability of SiC MOSFETs

Abstract: Silicon carbide (SiC) based metal-oxide semiconductor-field-effect-transistors (MOSFETs) show excellent switching performance and reliability. However, compared to silicon devices the more complex properties of the semiconductor-dielectric interface imply some natural peculiarities in threshold voltage variation. This paper analyzes threshold voltage hysteresis effects, bias temperature instability effects (BTI) and their relevance for the switching behavior. Most of the effects can be understood by means of simple physical models and do not harm reliability and performance of the device. It turns out that the standard norm test and readout procedures typically used to characterize threshold voltage and threshold voltage drifts for Si devices are insufficient and need to be adapted for SiC MOSFETs in order to get reproducible and solid results.

High-Pressure, High-Temperature Behavior of Silicon Carbide: A Review

Abstract: The high-pressure behavior of silicon carbide (SiC), a hard, semi-conducting material commonly known for its many polytypic structures and refractory nature, has increasingly become the subject of current research. Through work done both experimentally and computationally, many interesting aspects of high-pressure SiC have been measured and explored. Considerable work has been done to measure the effect of pressure on the vibrational and material properties of SiC. Additionally, the transition from the low-pressure zinc-blende B3 structure to the high-pressure rocksalt B1 structure has been measured by several groups in both the diamond-anvil cell and shock communities and predicted in numerous computational studies. Finally, high-temperature studies have explored the thermal equation of state and thermal expansion of SiC, as well as the high-pressure and high-temperature melting behavior. From high-pressure phase transitions, phonon behavior, and melting characteristics, our increased knowledge of SiC is improving our understanding of its industrial uses, as well as opening up its application to other fields such as the Earth sciences.

Identification and tunable optical coherent control of transition-metal spins in silicon carbide

Abstract: Color centers in wide-bandgap semiconductors are attractive systems for quantum technologies since they can combine long-coherent electronic spin and bright optical properties. Several suitable centers have been identified, most famously the nitrogen-vacancy defect in diamond. However, integration in communication technology is hindered by the fact that their optical transitions lie outside telecom wavelength bands. Several transition-metal impurities in silicon carbide do emit at and near telecom wavelengths, but knowledge about their spin and optical properties is incomplete. We present all-optical identification and coherent control of molybdenum-impurity spins in silicon carbide with transitions at near-infrared wavelengths. Our results identify spin S = 1/2 for both the electronic ground and excited state, with highly anisotropic spin properties that we apply for implementing optical control of ground-state spin coherence. Our results show optical lifetimes of ~60 ns and inhomogeneous spin dephasing times of ~0.3 μs, establishing relevance for quantum spin-photon interfacing. A study of defects in silicon carbide could enable the integration of quantum and standard telecommunications technologies. Defects in semiconductors are attractive systems for quantum technologies as quantum states can be prepared that have both long lifetimes and bright optical properties. Their optical transitions often lie outside of telecommunication wavelengths, however, which limit their potential use in and integration with standard communication technology. Tom Bosma from the University of Groningen and an international team of collaborators now show that they can optically control molybdenum defects in silicon carbide, which have transitions at the technologically important near-infrared wavelengths, showing that this is a promising platform for interfacing quantum and telecommunications technologies.

Mechanical and tribological behaviour of nano scaled silicon carbide reinforced aluminium composites

Abstract: This work assesses the impact of the presence of Nano scaled silicon carbide on the Mechanical & Tribological behavior of aluminium matrix composites. Aluminium matrix composites containing 0, 0.5,...

Identification and tunable optical coherent control of transition-metal spins in silicon carbide

Abstract: Color centers in wide-bandgap semiconductors are attractive systems for quantum technologies since they can combine long-coherent electronic spin and bright optical properties. Several suitable centers have been identified, most famously the nitrogen-vacancy defect in diamond. However, integration in communication technology is hindered by the fact that their optical transitions lie outside telecom wavelength bands. Several transition-metal impurities in silicon carbide do emit at and near telecom wavelengths, but knowledge about their spin and optical properties is incomplete. We present all-optical identification and coherent control of molybdenum-impurity spins in silicon carbide with transitions at near-infrared wavelengths. Our results identify spin $S=1/2$ for both the electronic ground and excited state, with highly anisotropic spin properties that we apply for implementing optical control of ground-state spin coherence. Our results show optical lifetimes of $\sim$60 ns and inhomogeneous spin dephasing times of $\sim$0.3 $\mu$s, establishing relevance for quantum spin-photon interfacing.

Direct laser sintering of reaction bonded silicon carbide with low residual silicon content

Abstract: Additive manufacturing (AM) techniques are promising manufacturing methods for the production of complex parts in small series. In this work, laser sintering (LS) was used to fabricate reaction bonded silicon carbide (RBSC) parts. First, silicon carbide (SiC) and silicon (Si) powders were mixed in order to obtain a homogeneous powder. This powder mixture was subsequently laser sintered, where the Si melts and re-solidifies to bind the primary SiC particles. Afterwards, these SiSiC preforms were impregnated with a phenolic resin. This phenolic resin was pyrolysed yielding porous carbon, which was transformed into secondary reaction formed SiC when the preforms were infiltrated with molten silicon in the final step. This resulted in fully dense RBSC parts with up to 84 vol% SiC. The optimized SiSiC combined a Vickers hardness of 2045 HV, an electrical conductivity of 5.3 × 103 S/m, a Young's modulus of 285 GPa and a 4-point bending strength of 162 MPa.

3-D Wire Bondless Switching Cell Using Flip-Chip-Bonded Silicon Carbide Power Devices

Abstract: This paper presents a three-dimensional (3-D) wire bondless power module using silicon carbide (SiC) power devices. Commercially available SiC power devices are designed for wire bonding. Wire bonds have an inherent parasitic inductance that limits high-frequency switching. This results in an underutilization of the full potential of SiC power devices, which have very low switching losses at high frequencies. Wire-bonded power modules run into a performance ceiling when it comes to ultrafast switching. This paper strives to provide a solution to this issue, which involves reconfiguring a commercially available bare die SiC power device into a flip-chip-capable device. A wire bondless SiC Schottky diode package was demonstrated and its performance was contrasted with a conventional wire-bonded package. A 24% reduction in the ON-state resistance was observed in the wire bondless package. As a next step, wire bondless SiC MOSFET packages were developed and tested in a half-bridge configuration in a highly integrated 3-D arrangement. This approach departs from the conventional concept of a power module—demonstrating a direct-bonded-copper-less and baseplate-less half-bridge switching cell. Double-pulse tests conducted on the cell showed >3× reduction in the parasitic inductance of the 3-D cell as compared with a conventional wire-bonded module.

GaN Integration Technology, an Ideal Candidate for High-Temperature Applications: A Review

Abstract: In many leading industrial applications such as aerospace, military, automotive, and deep-well drilling, extreme temperature environment is the fundamental hindrance to the use of microelectronic devices. Developing an advanced technology with robust electrical and material properties dedicated for high-temperature environments represents a significant progress allowing to control and monitor the harsh environment regions. It may avoid using cooling structures while improving the reliability of the whole electronic systems. As a wide bandgap semiconductor, gallium nitride is considered as an ideal candidate for such environments, as well as in high-power and high-frequency applications. We review in this paper the main reasons that offer superiority to GaN devices over better-known technologies such as silicon (Si), silicon-on-insulator, gallium arsenide (GaAs), silicon germanium (SiGe), and silicon carbide (SiC). The theory of operation and main challenges at high temperature are discussed, notably those related to materials and contacts. In addition, the main limitations of GaN, including the technological (thermal and chemical) and intrinsic (current collapse and device self-heating) features are provided. In addition, the GaN devices recently developed for high-temperature applications are examined.

Electrochemical characteristics of amorphous silicon carbide film as a lithium-ion battery anode

Abstract: The electrochemical reactions of SiC film with Li+ have been investigated by electrochemical characterization and X-ray photoelectron spectroscopy The SiC film is prepared by inductively-coupled-plasma chemical-vapor-deposition (ICP-CVD) technique and displays an amorphous state due to the low processing temperature (∼350 °C) An irreversible reaction of SiC with Li+ occurs with the formation of lithium silicon carbide (LixSiyC) and elemental Si, followed by a reversible alloying/dealloying reaction of the elemental Si with Li+ The 500 nm SiC film shows an initial reversible specific capacity of 917 mA h g−1 with a capacity retention of 410% after 100 cycles at 03C charge/discharge current, and displays much better capacity retention than the Si film (52%) It is found that decreasing the SiC thickness effectively improves the specific capacity by enhancing the reaction kinetics but also degrades the capacity retention (for 250 nm SiC, its initial capacity is 1427 mA h g−1 with a capacity retention of 257% after 100 cycles) The better capacity retention of the 500 nm SiC anode is mainly because residual SiC exists in the film due to its incomplete reaction caused by its lower reaction kinetics, and it has high hardness and can act as a buffer matrix to alleviate the anode volume change, thus improving the mechanical stability and capacity retention of the SiC anode

A review on the processing technologies of carbon nanotube/silicon carbide composites

Abstract: Due to the extraordinary electronic, mechanical, chemical, thermal, magnetic, and optical properties, carbon nanotube (CNT), an excellent one-dimensional nano-material, has been considered as a new filler for polymer, metal, and ceramic matrix composites with the main purpose of improving their mechanical performance, fracture behavior, and functional features. In the silicon carbide (SiC) ceramic field, there are many CNT reinforced SiC ceramic matrix composites and CNT/SiC hybrid structures, which have been investigated successfully using various of methods. This paper reviews the current status of researches and describes all different routes for effectively dispersing CNTs throughout SiC ceramic matrix, densifying composites, and synthesizing hybrid structures.

High temperature gas sensing performances of silicon carbide nanosheets with an n–p conductivity transition

Abstract: Fast and effective detecting of flammable and explosive gases in harsh environments (high temperature, corrosion atmosphere) is crucial for preventing severe accidents for the chemical industry, fuel cell applications and engine tests. Silicon carbide material is reported to be a good candidate for gas sensing devices applied in extreme conditions. Herein, high-temperature available silicon carbide nanosheets (SiC NSs) were synthesized from graphene oxide (GO) via a catalyst-free carbothermal method. The structure and composition of SiC NSs under different reaction conditions are carefully characterized. The received SiC NSs were firstly utilized as gas sensing materials for hazardous gases (acetone, ethanol, methanol and ammonia) at a high temperature (500 °C). Importantly, the SiC NSs sensors exhibited a fast response (8–39 s) and recovery (12–69 s) towards detecting gases. Besides, an n–p conductivity transition phenomenon is found and studied. This paper firstly proves that such SiC NSs has the potential to be used in gas sensing fields.

Designed synthesis of SiC nanowire-derived carbon with dual-scale nanostructures for supercapacitor applications

Abstract: The preparation of one-dimensional carbon materials with complex dual-scale nanostructures for supercapacitor applications still remains a challenge. Herein we report a simple strategy for electrosynthesis of silicon carbide nanowire (SiC NW)-derived carbon with dual-scale nanostructures for high performance supercapacitors. This method is highlighted by using solid oxide membrane technology to directly convert powdered silicon dioxide/carbon precursors into SiC NWs, and then the synthesized SiC NWs are further transformed into mesoporous silicon carbide-derived carbon nanowires (SiC-CDC NWs) via a subsequent in situ molten salt electrochemical etching process. Benefitting from their dual-scale nanostructures, these SiC-CDC NWs exhibit highly reversible specific capacitance of 260 F g−1 at 1 A g−1 and good cyclability (97.9% after 5000 cycles) in 6 M KOH aqueous solution without the need for doping the SiC-CDC NWs. It is suggested that this process is a promising general approach for synthesizing CDC materials with dual-scale nanostructures for energy storage applications.

Electrometry by optical charge conversion of deep defects in 4H-SiC

Abstract: Optically active point defects in various host materials, such as diamond and silicon carbide (SiC), have shown significant promise as local sensors of magnetic fields, electric fields, strain, and temperature. Modern sensing techniques take advantage of the relaxation and coherence times of the spin state within these defects. Here we show that the defect charge state can also be used to sense the environment, in particular high-frequency (megahertz to gigahertz) electric fields, complementing established spin-based techniques. This is enabled by optical charge conversion of the defects between their photoluminescent and dark charge states, with conversion rate dependent on the electric field (energy density). The technique provides an all-optical high-frequency electrometer which is tested in 4H-SiC for both ensembles of divacancies and silicon vacancies, from cryogenic to room temperature, and with a measured sensitivity of 41 ± 8 ( V / c m ) 2 / H z . Finally, due to the piezoelectric character of SiC, we obtain spatial 3D maps of surface acoustic wave modes in a mechanical resonator.