Showing papers on "Silicon carbide published in 1986"

An in situ HVEM study of dislocation generation at Al/SiC interfaces in metal matrix composites

Abstract: ANNEALED aluminum/silicon carbide (Al/SiC) composites exhibit a relatively high density of dislocations, which are frequently decorated with fine precipitates, in the Al matrix. This high dislocation density is the major reason for the unexpected strength of these composite materials. The large difference (10:1) between the coefficients of thermal expansion (CTE) of Al and SiC results in sufficient stress to generate dislocations at the Al/SiC interface during cooling. In thisin situ investigation, we observed this dislocation generation process during cooling from annealing temperatures using a High Voltage Electron Microscope (HVEM) equipped with a double tilt heating stage. Two types of bulk annealed composites were examined: one with SiC of discontinuous whisker morphology and one of platelet morphology. In addition, control samples with zero volume percent were examined. Both types of composites showed the generation of dislocations at the Al/SiC interface resulting in densities of at least 1013 m-2. One sample viewed end-on to the whiskers showed only a rearrangement of dislocations, whereas, the same material when sectioned so that the lengths of whiskers were in the plane of the foil, showed the generation of dislocations at the ends of the whiskers on cooling. The control samples did not show the generation of dislocations on cooling except at a few large precipitate particles. The results support the hypothesis that the high dislocation density observed in annealed composite materials is a result of differential thermal contraction of Al and SiC. The SiC particles act as dislocation sources during cooling from annealing temperatures resulting in high dislocation densities which strengthen the material.

Oxidation Kinetics of Silicon Carbide Crystals and Ceramics: I, In Dry Oxygen

Abstract: The oxidation kinetics of several single-crystal and polvcrystalline silicon carbide materials and single-crystal silicon in dry oxygen over the temperature range 1200° to 1500°C were fitted to the linear-parabolic model of Deal and Grove. The lower oxidation rates of silicon carbide compared to silicon can be rationalized by additional consumption of oxidant in oxidizing carbon to carbon dioxide. The (000J) Si face of the silicon carbide platelets exhibited lower parabolic oxidation rates than the (0001) C face, by a factor of 10 at 1200°C. Apparent activation energies increased from a value of ∼120 kJ/mol below 1400°C to a value of ∼300 kJ/mol above this temperature. The (0001) Si face exhibited this high activation energy over the entire temperature range. The controlled nucleation thermally deposited material exhibited the highest oxidation rates of the polycrystalline materials followed by the hot-pressed and sintered α-silicon carbides. In general, the oxidation rates of the polycrystalline materials were bracketed by the oxidation rates of the basal planes of the single-crystal materials. Higher impurity concentrations and higher density of nucleation sites led to a greater susceptibility to crystallization of the scale which significantly complicated the oxidation behaviors observed. When crystallization of the oxide scale occurred in the form of a layer of spherulitic cristobalite crystals, a retardation of the oxidation rates was observed. An accelerated oxidation behavior was found when this coherent layer was superseded by the formation of fine mullite crystals.

Synthesis of continuous silicon carbide fibre: Part 4The structure of polycarbosilane as the precursor

Abstract: The structure of polycarbosilane is represented by three structural elements, but their quantification is difficult. Polycarbosilanes were synthesized by three methods and the respective molecular structures were examined by measurements of the molecular weight and the intrinsic viscosity, infrared, ultraviolet,1H-,13C- and29Si-NMR spectral measurements, and chemical analysis. The three structural elements (SiC4, SiC3H, SiCxSi4−x) in the polycarbosilane molecule were determined quantitatively. By the comparison between1H-NMR spectral data and calculation assuming a linear chain structure, the number of linkages in the unit consisting of ten silicon atoms was estimated to be 3 to 4. This result is in agreement with the result from the intrinsic viscosity; it was found that the shape of the polycarbosilane molecule is planar.

Microstructural evolution in reaction-bonded silicon carbide

Abstract: A detailed microstructural investigation of reaction-bonded silicon carbide has been performed using both fully-bonded and quenched samples and other specially prepared specimens containing large original single crystals of known crystallographic habit. The development of the epitaxial SiC overgrowth on the original SiC particles has been followed and found to proceed by the progressive growth and coalescence of identically-oriented nuclei. This epitaxial layer grows with a habit characteristic ofβ (cubic) SiC and then transforms toα-SiC in the high temperature region behind the reaction front. The formation of faceted grain boundaries is explained by this growth morphology. Furthermore, SiC:SiC grain boundaries, SiC:SiC epitaxial boundaries and SiC:Si interfaces have all been characterized by TEM techniques. The grain boundaries are of particular interest since they usually comprise a thin (∼1 nm) layer of amorphous SiC with occasional suicide and graphite inclusions. The general cleanliness of the vast majority of interfacial area is a result of the removal of the impurities insoluble in SiC by liquid silicon moving through the sample. The overall distribution of impurities is discussed. Other microstructural features have been characterized and texturing due to original particle alignment during fabrication of the green compact investigated. The control of the mechanical properties of reaction-bonded silicon carbide by these various microstructural features is discussed. A basis for an explanation of the interesting trace-impurity-controlled contrast seen in secondary electron images of these materials is also established.

Tension and flexural strength of silicon carbide fibre-reinforced glass ceramics

Abstract: The use of silicon carbide-type fibres to reinforce lithium aluminosilicate glass ceramics results in composites with exceptional levels of strength and toughness. It is demonstrated that composite strength and stress-strain behaviour depend onin situ fibre strength, matrix composition, test technique and atmosphere of test. Both linear and non-linear tensile stress-strain curves are obtained with ultimate strengths at 22° C approaching 700 MPa and failure strains of 1%. Flexure tests performed at up to 1000° C in air are compared with data obtained in argon to demonstrate a significant dependence of strength and failure mode on test atmosphere. Finally, glass ceramic matrix composite performance is compared with a silicon carbide fibre-reinforced epoxy system to demonstrate the importance of matrix failure strain on strength and stress-strain behaviour.

Tailoring Multiphase and Composite Ceramics

Abstract: Processing and Fabrication of Multiphase Ceramics.- Sintering of Multiphase Ceramics.- The Morphological Stability of Continuous Intergranular Phases.- Role of Shear in the Sintering of Composites.- HIP of Liquid Phase Sintered Ceramic Composites.- Sinterable Yttria-Doped Zirconia Powders Chemically Coprecipitated in Non-Aqueous Medium.- Microstructural and Chemical Aspects of a Strontia Sintering Aid on Mg-PSZ.- Phase Relationships in Y-Si-A1-O-N Ceramics.- The Fabrication of Composite O'-B' Sialon Ceramics.- Ceramic Eutectic Composites.- Nickel Oxide-Based Aligned Eutectics.- Imperfections in the Directionally Solidified Structure of NiO-CaO Eutectic.- CVD-Processing of Ceramic-Ceramic Composite Materials.- CVD Fabrication of In-situ Composites of Non-oxide Ceramics.- Preparation of Boron Nitride/Boron Carbide Ceramics by Pyrolysis of Boric Acid-Glycerin Condensation Product.- Porous and Dense Composites for Sol-Gel.- Non-Equilibrium Surface Conditions and Microstructural Changes Following Pulsed Laser Irradiation and Ion Beam Mixing of Ni Overlayers on Sintered Alpha-SiC.- Structure-Property Relations in Multiphase Ceramics.- Quantitative Microstructural Characterization and Description of Multiphase Ceramics.- Displacive Transformation Mechanisms in Zirconia Ceramics and Other Non-Metals.- On Precipitate Morphology in ZrO2 ?-Al2O3, FeTiO3 Matrices.- Particle Toughening in Partially Stabilized Zirconia Influence of Thermal History.- Fabrication and Properties of Transformation-Toughened Sodium Beta"-Alumina.- Phase Transformation and Toughening in MgO Dispersed with ZrO2.- Effect of Impurities on Microstructure and Mechanical Properties of Si3N4-TiC Composites.- On the Microstructure and Hardness Characteristics of Composite Ceramics for Tool Applications.- Mechanical Properties and Wear Resistance of Silicon Nitride-Titanium Carbide Composites.- The Structure and Properties of Interfaces in Reaction-Bonded Silicon Carbides.- Some Factors Affecting Mechanical and Microstructural Anisotropy in Reaction-Bonded Silicon Carbides.- Microstructure-Mechanical Property Relationships in 94% Alumina Ceramics.- New Low Expansion Magnetic Materials-A Composite Approach.- Multiphase Electroceramics.- Electroceramic Composites.- Finite Element/Difference Modeling of Electroceramics.- Multiphase Interaction for Seeking Exotic Phenomena.- Processing of Heterogeneous Ceramics for Dielectric Applications.- Dielectric and Electrical Properties of BaTiO3 Composites.- Composite Piezoelectric Sensors.- Wave Absorption in Piezoceramic-Polymer Composites.- Structured Macrovoids in Ceramic PZT.- Composite Thermistors.- Grain Resistivity and Conduction in Metal Oxide Varistors.- Influence of Microstructure and Chemistry on the Electrical Characteristic of ZnO Varistors.- Influence of Chemical Composition on the Barrier Height in Zn Varistors.- Polycrystalline H3O+-?/?" Alumina: A Designed Composite for Steam Electrolysis.- Fiber and Whisker Reinforced Composites.- The Development of Fiber Reinforced Glasses and Glass Ceramics.- Interfacial Characterization of Glass and Glass-Ceramic Matrix/Nicalon SiC Fiber Composites.- Fatigue Behavior of Silicon Carbide Fiber Reinforced Lithium-Alumino-Silicate Glass-Ceramics.- Fiber Reinforced Composites Via the Sol/Gel Route.- Fiber-Matrix Interactions in Carbon Fiber/Cement Matrix Composites.- Morphological and Mechanical Characterization of Ceramic Composite Materials.- Toughness Anisotropy of a SiC/SiC Laminar Composite.- Whisker Reinforced Ceramic Composites.- Whisker-Reinforced Zirconia-Toughened Ceramics.- Si3N4-SiC Whisker Composite Material.- Mechanical Properties of SiC Fiber-Reinforced Reaction-Bonded Si3N4 Composites.- Surface Energy as an Indicator of Interfacial Mechanical Response.- High Temperature Multiphase Ceramics.- Prospects for Ultra-High-Temperature Ceramic Composites.- Microstructural Engineering of Ceramics for High-Temperature Application.- Tailoring of the Thermal Transport Properties and Thermal Shock Resistance of Structural Ceramics.- Creep Rupture of Siliconized Silicon Carbide.- High Temperature Mechanical Properties of Siliconized Silicon Carbide Composites.- Contributors.

Effective sintering aids for silicon carbide ceramics: reactivities of silicon carbide with various additives

Abstract: Effective sintering aids for SiC ceramics are discussed on the basis of their reactivities with various sintering aids around sintering temperatures (2300 to 2400 K). The free energy consideration of the reactions suggests that metals and metal oxides which do not decompose SiC in the sintering process are effective as sintering aids for SiC ceramics.

Silicon carbide whisker reinforced ceramic composites and method for making same

Abstract: The present invention is directed to the fabrication of ceramic composites which possess improved mechanical properties especially increased fracture toughness. In the formation of these ceramic composites, the single crystal SiC whiskers are mixed with fine ceramic powders of a ceramic material such as Al2 O3, mullite, or B4 C. The mixtures which contain a homogeneous dispersion of the SiC whiskers are hot pressed at pressures in a range of about 28 to 70 MPa and temperatures in the range of about 1600° to 1950° C. with pressing times varying from about 0.75 to 2.5 hours. The resulting ceramic composites show an increase in fracture toughness of up to about 9 MPa.m1/2 which represents as much as a two-fold increase over that of the matrix material.

Surface Characterization of Silicon Nitride and Silicon Carbide Powders

Abstract: The nature and composition of the surfaces of silicon nitride and silicon carbide powders were investigated using high voltage and high resolution transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and secondary ion mass spectrometry (SIMS). An amorphous oxide (or oxygen-rich) layer, approx. =3-5 nm thick, present on the powder surfaces forms strong bridges between particles. Both XPS and SIMS show that oxygen is the major impurity on the powder surfaces, but minor impurities such as chlorine, fluorine, carbon, iron and sodium are also revealed. The extent of the oxide layer was reduced substantially by washing the powder in anhydrous hydrofluoric acid or by treatment in an argon/hydrogen gas mixture at approx. =1300/sup 0/C. Surface treatment in the gas mixture did not cause further agglomeration of the powder.

Thermodynamics of the Si-C-O system for the production of silicon carbide and metallic silicon

Abstract: The predominance diagrams of the Si-C-O system for 1350 to 2200 °C have been constructed thermodynamically by taking into account the presence of liquid silicon monoxide. The high-temperature behavior of various feeds, such as the SiO2-C and SiO2-SiC systems, have been calculated as functions of mixing ratio and reaction temperature by using the method of equilibrium mass-balance. For an efficient SiC-making, a charge having a C/Si ratio of 2.91 should be heated between 2035 and 2045 °C, where SiC crystals can be grown mainlyvia gas-phase reactions of SiO(g). Metallic silicon cannot be produced unless a charge of the Si-C-O system is heated above 2037 °C. In Si-making, liquid SiO plays an important role in that the yield can be improved substantially by enhancing the condensation of SiO gas in the upper cooler part of the furnace. This work also lends thermodynamic proof and support to the double-reactor model, in which a greater fixation of ascending SiO gas on carbon as SiC is considered essential for obtaining a higher silicon yield in industrial furnaces. Some fundamental strategies useful to the improvements of commercial Si- and SiC-making operations have been described quantitatively.

Process for preparing a silicon carbide device

Abstract: A silicon carbide layer(s) is provided on a silicon substrate. If necessary, a desired pattern of the silicon carbide layer(s) is allowed to remain, while the other portion(s) is embedded with SiO2. If necessary, the silicon carbide layer(s) may be constituted of a barrier layer and a device-forming layer. A layer capable of easily forming an insulating layer, such as a polycrystalline silicon layer, is provided on the silicon carbide layer to form first electrodes, followed by insulation of the surface, such as oxidation of the surfaces of the first electrodes and the silicon carbide layer. Second electrodes are further formed in self alignment by utilizing the insulating layer of the surface of the first electrodes. This process is useful in preparation of a silicon carbide device capable of operation at high temperatures.

Electrochemical converters and combined cycle systems

Abstract: A compact, electrochemical converter can be achieved using thin plates of electrolyte and interconnector. Impermeable, straight, thin plates of solid-oxide electrolyte are fabricated by high energy plasma spray methods under controlled temperature conditions. Thin sheets of nickel alloys or silicon carbide or platinum alloys can be used to form the interconnector. The electrolyte and interconnector plates can be assembled into a converter stack at an elevated temperature such that upon cooling and during subsequent operational temperature excursions, the electrolyte plates will remain in compression. The stacks can be connected together to form modules which can be used as stand-alone electricity generators or used in combined cycle, cogeneration and gasifier systems.

Experimental 3C-SiC MOSFET

Abstract: Cubic-SiC (3C-SiC) MOSFET's were successfully fabricated for the first time on a 3C-SiC film heteroepitaxially grown on an Si substrate. The device showed acceptable static characteristics. A novel device structure was devised, which enabled the use of conventional equipment for silicon devices, and eliminated dedicated processes for a stable and rigid SiC film.

Friction and Wear of Hot Pressed Silicon Nitride and Other Ceramics

Abstract: An investigation was conducted to determine the friction and wear characteristics of hot-pressed silicon nitride. Sliding produced wear debris and a damaged surface. The physical and crystallographic morphology of surfaces was compared with that of diamond ground surfaces. Wear tests were done with pin-on-disk apparatus at a load of 10N with various sliding speeds to 780 mm/s, and in four different environments which included in dry nitrogen, in air at humidities of 50 percent RH and 90 percent RH, and in distilled water. The results of the wear experiments indicated that residual α-silicon nitride was transformed into β-silicon nitride. Adsorbed water appeared to enhance plastic flow of the surface and reduced both the wear rate and friction. A second investigation was conducted to correlate the coefficient of friction with the fracture toughness of silicon nitride, silicon carbide, aluminum oxide and zirconium oxide. The friction experiments were done in reciprocating sliding, using spherical diamonds. Two tip radii, 0.005 mm and 0.1 mm were used over a range of load of 0.1 to 3N and a speed of 0.17 mm/s. The coefficient of friction was found to be inversely correlated with fracture toughness of all four ceramics in several conditions. Frictional anisotropy was also observed in the hot-pressed silicon nitride.

Alumina composite body and method for its manufacture

Abstract: An alumina composite body comprising a plurality of elongated alumina elements oriented in random directions and interconnected so as to constitute a porous matrix, and aluminum and silicon tightly filling the porous matrix; and a method of manufacturing an alumina composite body comprising reacting a body of silica, or a body of a silicon compound such as silicon carbide or silicon nitride which has been at least partially oxidized to produce silica, with aluminum so as to change the silica into alumina.

Synthesis of continuous silicon carbide fibre: Part 5 Factors affecting stability of polycarbosilane to oxidation

Abstract: Polycarbosilane (PC) was obtained by adding bolodiphenylsiloxane (BDPSO) as a reaction accelerator to poly(dimethylsilane) (PDMS), then the thermal decomposition and condensation at various conditions were determined. The molecular weight distribution and the reactivity with oxygen of PC differ with the quantity of BDPSO added, the reaction temperature and the reaction time. The larger the amount of BDPSO, the higher the reaction temperature and the longer the reaction time, the larger becomes the molecular weight of PC. In addition, the higher the reaction temperature, the more stable becomes PC for oxidation. The synthesized PC was spun and the fibre was heated in air at low temperature for curing. The cured fibre was then heat-treated to obtain the SiC fibre. Properties of the SiC fibre are closely related to the oxidation properties of the PC.

Method for producing composite material having an aluminum alloy matrix with a silicon carbide reinforcement

Abstract: Reinforced composite aluminum-matrix articles containing up to 20%, by volume, silicon carbide fibers or particles, are produced by a casting process wherein about 4% to about 7%, by weight, of magnesium is included in the aluminum matrix alloy to facilitate wetting of the reinforcing material and ready dispersal thereof with the matrix alloy while the alloy is completely molten and thereafter hot working the composite at a temperature between the liquidus and solidus temperatures of the aluminum alloy matrix. The matrix is characterized by a microstructure wherein fine precipitates appear in the vicinity of SiC particles or fibers, and by high hardness and strength without further heat treatment.

Silicon carbide whisker-zirconia reinforced mullite and alumina ceramics

Abstract: The flexural strength and/or fracture toughness of SiC whisker-reinforced composites utilizing mullite or alumina as the matrix material for the composite are increased by the addition of zirconia in a monoclinic or tetragonal phase to the matrix. The zirconia addition also provides for a lower hot-pressing temperature and increases the flexural strength and/or fracture toughness of the SiC whisker-reinforced composites over SiC whisker-reinforced composites of the similar matrix materials reinforced with similar concentrations of SiC whiskers.

Production of aluminum-SiC composite using sodium tetrasborate as an addition agent

Abstract: Reinforced composite aluminum-matrix articles containing silicon carbide fibers or particles, are produced by a casting process wherein the silicon carbide fibers or particles are mixed with dehydrated sodium tetraborate and mixed with molten aluminum or aluminum alloy whereby wetting of the reinforcing material and ready dispersal thereof in the aluminum matrix alloy is facilitated.

Composite materials having a matrix of magnesium or magnesium alloy reinforced with discontinuous silicon carbide particles

Abstract: Reinforced composite magnesium-matrix articles, containing silicon carbide fibers or particles, are produced by a casting process wherein a small amount of lithium, less than about 0.7% by weight, is included in a melt of magnesium matrix alloy to facilitate wetting of the reinforcing material and ready dispersal thereof in the magnesium matrix alloy.

Interaction kinetics of boron carbide and silicon carbide with liquid aluminium

Abstract: The interaction of boron carbide and silicon carbide with liquid aluminium at 1000 K was studied when the melt was not stirred. Electron and X-ray diffraction methods were used to identify Al4C3 and AlB2 phases in the Al-B4C system, while the Al4C3 phase only was identified in the Al-SiC system. All the phases were found to grow when the metal crystallized from the supersaturated solution in the shape of rectilinearly faceted crystals. By weighing the specimens prior to and following contact with the liquid metal, kinetic peculiarities of the dissolution of carbide were established. Constants of boron and carbon dissolution from carbides in liquid aluminium were determined. The results are compared with those obtained using quantitative chemical analysis for boron carbide and aluminium carbide. The higher dissolution rate of boron carbide as compared with that of silicon carbide is accounted for by the peculiar structure of the solid.

Method of fabricating single-crystal substrates of silicon carbide

Abstract: A single-crystal substrate of silicon carbide comprising a single-crystal substrate member of a material other than α-SiC, and a single-crystal layer of α-SiC formed over the substrate member with a ground layer provided between the substrate member and the single-crystal layer, the ground layer comprising a single-crystal layer of nitride of AlN, GaN or Al x Ga 1-x N (0

Process for production of metal matrix composites by casting and composite therefrom

Abstract: Silicon carbide particulate reinforced aluminum alloy matrix composites are formed using techniques which include agitation of a melt of aluminum alloy, containing magnesium, and silicon carbide particulates in a manner whereby the silicon carbide particles are maintained, during agitation, within the body of the melt; the agitation, which involves shearing or wiping of the particles in the liquid, is carried out under vacuum; and may involve incorporation into the melt of an additional amount of magnesium such that that amount compensates for the amount of magnesium which segregates to the carbide surfaces, and is sufficient to effect strengthening of the resulting composite. Aluminum alloy matrix composites, containing copper, are produced using similar agitation and mixing procedures, with the copper being incorporated in such a way as to discourage reaction between the copper and SiC particles.

Ground-state properties of polytypes of silicon carbide.

Abstract: The ground-state properties of cubic silicon carbide are calculated as a stepping stone towards a description of the polytypes of silicon carbide The pseudopotential-density-functional method is used to calculate the self-consistent valence charge density as well as the equilibrium lattice constant and bulk modulus Comparison with experimental data and earlier less rigorous calculations shows good agreement A strategy is indicated to obtain a description of all polytypes

Synthesis of Ultrafine Silicon Carbide Powders in Thermal Arc Plasmas

Abstract: Ultrafine s-SiC powders are synthesized in thermal plasmas by a reaction between methane and silicon monoxide. The reaction is carried out in an unconfined plasma jet (22.5 kW) operating at atmospheric Ar pressure. High temperatures (> 10 000 K) combined with ultrarapid quench rates (? 106 K/s) of the plasma lead to a high degree of supersaturation of the chemical vapor, resulting in homogeneous nucleation of ultrafine particles. Product characterizations are pursued with X-ray diffraction analysis, X-ray photoelectron spectroscopy (XPS), scanning, and transmission electron microscopy. The maximum SiC yield determined by thermogravimetric analysis (TGA) is 97.3 percent. Particle size analyses show a bimodal distribution with the majority of the particles falling in a size range from 2 to 40 nm. Triangular and hexagonal SiC particles are observed throughout this work and the nucleation and growth of these particles are discussed.

Sintering behaviour and properties of SiCAION ceramics

Abstract: Silicon carbide (SiC), aluminium oxycarbide (AI2OC), and aluminium nitride (AlN) all have the same wurtzite crystal structure and can be processed so as to form SiCAION, an acronym for the solid solution. This paper describes processing of SiC-Al2OC ceramics by pressureless reactive sintering and gives mechanical property data on the same. Experiments showed that densification occurred by a liquid-phase sintering mechanism. Both alpha and beta SiC up to a particle size of 5μm were used to form the solid solution, boron additions were not necessary to promote densification, and densities greater than 97% of the theoretical were achieved by pressureless sintering. SiC-Al2OC ceramics, containing minor amounts of AIN, were fabricated from conventional raw materials. Phase identification by X-ray diffraction and metallography showed that the materials consisted of two phases: SiCAION and SiC. Mechanical property data were obtained on pressureless sintered and hot-pressed materials. Hot-pressed materials had room-temperature strengths in excess of 600 MPa, hardness greater than 25 G Pa, and fracture toughness greater than 4 M Pa m−1/2. Pressureless sintered bars had bend strengths in excess of 300 M Pa.

Glass ceramic precursor compositions containing titanium diboride

Abstract: Glass ceramic precursor compositions comprise from about 15 to about 75 percent by weight of titanium diboride and from about 10 to about 85 percent by weight of a silica compound, such as colloidal silica. The glass ceramic precursor compositions may also contain an amount up to about 60 percent by weight of an intemetallic compound, such as silicon carbide. Upon firing of the precursor compositions, glass ceramic materials are formed which are useful at high temperatures and in harsh environments as sealants, as protective coatings or as articles of manufacture.

A Model for Silicon Self‐Diffusion in Silicon Carbide: Anti‐Site Defect Motion

Abstract: A simple defect interaction model was developed that explains the identical activation energies observed for carbon and silicon diffusion in single-crystal silicon carbide. In accord with experimental measurement of nonstoichiometry, the model requires a substantial concentration of silicon anti-site defects. The diffusion of silicon is limited by the motion of these defects; this is suggested to occur by their interaction with carbon vacancies. The model predicts that boron doping will increase both carbon and silicon diffusion coefficients.

Behavior of inversion layers in 3C silicon carbide

Abstract: A study on the field-induced surface-charge region in 3C silicon carbide (SiC) using 1 MHz capacitance-voltage (C-V) measurements at room temperature is here reported. A double column mercury probe was used on oxidized SiC substrates to form metal-oxide-semiconductor (MOS) structures. These structures were characterized in terms of the substrate doping profile, effective fixed oxide charge, and interface trap density. A distinctive feature of the MOS C-V curves from accumulation to inversion is that after going into deep depletion the capacitance rises to its equilibrium inversion level during the voltage sweep. Capacitance transient measurements indicate that the minority-carrier generation occurs at the SiO2/SiC interface.