Structure Of Silicon Carbide Research Articles

Imprinting the Polytype Structure of Silicon Carbide by Rapid Thermal Processing

Silicon carbide is a material with a multistable crystallographic structure, i.e., a polytypic material. Different polytypes exhibit different band gaps and electronic properties with nearly identical basal plane lattice constants, making them interesting for heterostructures without concentration gradients. The controlled formation of this heterostructure is still a challenge. The ability to adjust a defined temperature–time profile using rapid thermal processing was used to imprint the polytype transitions by controlling the nucleation and structural evolution during the temperature ramp-up and the steady state. The influence of the linear heating-up rate velocity during ramp-up and steady-state temperature on the crystal structure of amorphized ion-implanted silicon carbide layers was studied and used to form heteropolytype structures. Integrating the structural selection properties of the non-isothermal annealing stage of the ion-implanted layers into an epitaxial growth process allows the imprinting of polytype patterns in epitaxial layers due to the structural replication of the polytype pattern during epitaxial growth. The developed methodology paves the way for structural selection and vertical and lateral polytype patterning. In rapid thermal chemical vapor deposition, the adjustment of the process parameters or the buffer layer allowed the nucleation and growth of wurtzite silicon carbide.

The Role on Wettability of Electroless Copper Coating in Porous Silicon Carbide Structures

Copper (Cu) coatings of porous silicon carbide (SiC) structures were deposited using the electroless metal coating method. Ceramic slurry consisting of silicon carbide, bentonite and pure water was...

Nickel coating performance of porous SiC structures by electroless coating

In this study, the effect of nickel coating and performance of porous silicon carbide structures, by an electroless coating method, was investigated. Silicon carbide powders of 30 μm and bind bentonite powders of 20 μm were mixed, and a slurry was obtained. This mixture was then absorbed into the polymeric sponge template. The structures were kept in the furnace until 1300 °C; then both water and polyurethane were removed from the structure, and the remaining particles were sintered to each other. In order to improve the wetting behavior of the aluminum composite, the porous silicon carbide structures obtained were coated with the electroless coating method. AlSi10Mg aluminum casting alloy was infiltrated into the nickel-coated porous structures by a pressure die casting method. In order to examine the coating performance, microstructure, and element analysis, both porous silicon carbide structures and aluminum composites were performed. Density, according to the Archimedes principle, and porosity measurements were made on all aluminum composites. As a result, the positive effect of nickel coating on wetting in aluminum matrix composite systems was confirmed by obtaining a value close to theoretical density with 99.75%.

A Review of Switching Oscillations of Wide Bandgap Semiconductor Devices

Wide bandgap (WBG) devices offer the advantages of high frequency, high efficiency, and high power density to power converters due to their excellent performance. However, their low parasitic capacitance and fast switching speed also make them more susceptible to switching oscillations. The switching oscillations can cause voltage and current overshoots, shoot-through, electromagnetic interference, additional power loss, and even device damage, which can seriously affect the performance of power converters and systems. However, a comprehensive and in-depth overview is lacking on this topic. This article reviews the types, the causes and negative effects, the effects of parasitic parameters and suppression methods of these switching oscillations, which is helpful for practical engineering. First, the switching oscillations are divided into different types, and their causes and negative effects are reviewed. Then, the effects of different parasitic parameters on the switching oscillations are overviewed. It is found that due to the different physical structures of silicon carbide metal-oxide-semiconductor field-effect transistors, enhancement-mode gallium nitride high-electron mobility transistors (eGaN HEMTs), and cascode GaN HEMTs, the effects are also different. Finally, the main methods of suppressing the switching oscillations are summarized, and the advantages and disadvantages of these methods are presented. Furthermore, future research works on this topic and the conclusion of this paper are drawn, which will help readers deepen their understanding of the switching oscillations of WBG devices, and inspire readers to better use WBG devices for high-frequency and high-efficient power conversion.

Recrystallization of the Structure of Silicon Carbide under Ion Irradiation

Silicon carbide was irradiated with aluminum ions at an energy of 190 keV with fluences of $$2\times 10^{13}{-}5\times 10^{14}$$ ion/cm $${}^{2}$$ . The temperature of the target during irradiation was 300–500 $${}^{\circ}$$ C or it was kept at room temperature. It is shown that the presence of nitrogen in the structure of silicon carbide erodes the edge of the interband absorption. After irradiation at room temperature, the structure is disordered to form Si–Si and C–C compounds, as well as 3C–SiC. According to the absorption spectra, when the target temperature is increased during irradiation to 500 $${}^{\circ}$$ C, the structure of silicon carbide recrystallizes up to the initial state.

First principles study of structural, electronic and magnetic properties of transition metals doped SiC monolayers for applications in spintronics

First principles investigations were carried out to explore the prospects of using silicon carbide (SiC) monolayers in spintronics. The structural, electronic and magnetic properties of Ti, V, Cr, Mn and Fe doped SiC monolayers were studied in detail in framework of density functional theory (DFT). These dopants changed the band structure of SiC by introducing gap states and thus altered the electronic and magnetic character of the host. The results indicated that Ti did not produce any magnetic state whereas Mn and Cr exhibited ferromagnetism (FM), and V as well as Fe displayed anti-ferromagnetism (AFM) as stable configurations in the matrix. The calculated values of magnetic moments are 0 μB, 1.24 μB, 2.37 μB, 3.01 μB, and 2.21 μB for dopants Ti, V, Cr, Mn and Fe respectively in the host. The dopants reveal 3d-2p hybridization with exchange interactions taking place through charge hopping. The analysis indicated that magnetic exchange takes place in Mn:SiC and Fe:SiC via super-exchange whereas in Cr:SiC via double exchange interactions. The Mn doped SiC monolayer appeared to offer highest Curie temperatures with half metallic nature and highest magnetic moment which points to its suitability as potential diluted magnetic semiconductor for different spintronic applications.

Ultra-sensitive UV sensors based on porous silicon carbide thin films on silicon substrate

In this report, high-performance ultraviolet (UV) detectors were designed based on porous silicon carbide (SiC) thin films on silicon (Si) substrate. The results can broaden the applications of porous SiC structures in sensing applications. Here, n-type Si (100) was used as a substrate for epitaxial growth of SiC thin films. In order to fabricate porous SiC thin films, a two-electrode, photo-assisted electrochemical etching process was carried out using an integrated current source. The improvement in optical characteristics of porous SiC/Si was reported by tuning the anodization current density. It was illustrated that current density is an effective parameter for controlling the morphology of porous samples. The optical properties of samples were studied using photoluminescence (PL) and optical reflectometry. The results showed that by applying an optimized value of etching current density, the optical reflectivity is decreased which is due to the elevated specific surface area of porous samples that captures the incident light and reduces the reflection. Enhancement in porosity of optimized porous SiC/Si sample was illustrated by its elevated PL intensity. The UV sensing capability of fabricated metal-semiconductor-metal (MSM) detectors based on porous SiC/Si samples with different etching current densities was investigated. The device based on the optimized porous sample showed enhanced sensitivity (54.51) to UV illumination due to the elevated photogenerated current. Moreover, the ultrafast sensing behavior of this device indicates its improved optoelectrical performance in UV detection.

Структурные и оптические характеристики ультрафиолетовых 4H-SiC-детекторов, облученных ионами аргона

Abstract The paper presents the results of a study of the effect of irradiation with heavy Ar ions on the structural and optical characteristics of 4H-SiC. It has been shown that as a result of already single irradiation with Ar ions with an energy of 53 MeV with a fluence of 1٠1010 cm-2, at least 2 powerful local regions with negative deformation prevail in the structure of silicon carbide. Along with this, a region with positive deformation is also observed in the structure. The formation of localized clusters with negative and positive deformations, along with the undisturbed matrix, is accompanied by the formation of linear type defects that partially relieve stresses in the structure. It is assumed that the resulting complex defect structure upon irradiation with Ar ions provides the effect of gettering of point defects and leads to the quantum efficiency of 4H-SiC UV photodetectors at the level of the initial samples.

Detonation synthesis of silicon carbide nanoparticles

Detonation of explosives was used to synthesize silicon carbide nanoparticles. Polycarbosilane was added to a mixture of 1,3,5-Trinitro-1,3,5-triazinane and 2,4,6-trinitrotoluene, which was subsequently detonated in an enclosed chamber backfilled with inert gas. X-ray diffraction analysis of the detonation soot was consistent with the presence of crystalline silicon with a diamond cubic structure and cubic silicon carbide, along with amorphous material. Further analysis by transmission electron microscopy revealed the presence of crystalline angular particles. High resolution imaging showed that the particles contained numerous stacking faults along the [111] direction and had an interplanar spacing of 2.5 Å, both of which are characteristic of beta (cubic) silicon carbide. This is the first report of the detonation synthesis of silicon carbide by dissolving a silicon-containing precursor into an explosive composition.

Influence of Aluminum Additives on the Content and Parameters of the Fine Structure of Titanium Silicon Carbide in SHS Powders

The dependence of the phase composition and parameters of a fine structure of titanium silicon carbide in powders formed by the self-propagating high-temperature synthesis on the aluminum concentration in the 5Ti/2Si/1C reaction mixture is investigated. The aluminum content is varied in a range of 0.1–0.4 mole fraction with the conservation of the total carbon content. It is established that the additives of aluminum not only affect the yield of titanium silicon carbide, but also promote the preferential formation of Ti5Si3 in synthesis products instead of TiSi2 identified in powders containing no aluminum. The introduction of a small amount of aluminum (0.1 mole fraction) leads to the formation of the Ti3Si1 – xAlxC2 solid solution and makes it possible to decrease the content of impurity phases in SHS powders by 6%. The silicon carbide concentration in SHS powders decrease at a higher aluminum content in the reaction mixture, while that of binary compounds (TiC, Ti5Si3, TiAl) correspondingly increases. No noticeable effect from the introduction of aluminum on the parameters of the crystal lattice of titanium silicon carbide in SHS powders is found in concentration limits of 0.1–0.25 mol %. A noticeable increase in parameters of a and c for Ti3Si1 – xAlxC2 (from a = 3.067 A, c = 17.67 A to a = 3.07 A, c = 17.73 A) with the conservation of the c/a ratio in limits of known values (c/a = 5.78) is observed only with the aluminum concentration of 0.4 mole fraction. The crystallite size of titanium silicon carbide depends, first and foremost, on the combustion parameters. At the same time, the deformation of the crystal lattice of Ti3Si1 – xAlxC2 in SHS powders increases monotonically with an increase in the aluminum content in the reaction mixture in the concentration range under study.

Crystal structures and the electronic properties of silicon-rich silicon carbide materials by first principle calculations

Silicon carbide has been used in a variety of applications including solar cells due to its high stability. The high bandgap of pristine SiC, necessitates nonstoichiometric silicon carbide materials to be considered to tune the band gap for efficient solar light absorptions. In this regards, thermodynamically stable Si-rich SixC1-x materials can be used in solar cell applications without requiring the expensive pure grade silicon or pure grade silicon carbide. In this work, we have used density functional theory (DFT) to examine the stability of various polymorphs of silicon carbide such as 2H–SiC, 4H–SiC, 6H–SiC, 8H–SiC, 10H–SiC, wurtzite, naquite, and diamond structures to produce stable structures of Si-rich SixC1-x. We have systematically replaced the carbon atoms by silicon to lower the band gap and found that the configurations of these excess silicon atoms play a significant role in the stability of Si-rich SixC1-x. Hence, we have investigated different configurations of silicon and carbon atoms in these silicon carbide structures to obtain suitable SixC1-x materials with tailored band gaps. The results indicate that 6H-SixC1-x is thermodynamically the most favorable structure within the scope of this study. In addition, Si substitution for C sites in 6H–SiC enhances the solar absorption, as well as shifts the absorption spectra toward the lower photon energy region. In addition, in the visible range the absorption coefficients are much higher than the pristine SiC.

Experimental investigations of thermal modal parameters for a C/SiC structure under 1600 °C high temperature environment

This work aims to investigate the thermal–mechanical behavior of a carbon fiber reinforced silicon carbide (C/SiC) structure under 1600 °C high temperature environment. In this test, both the contact and non-contact measurement are used. Four laser vibrometers were used for non-contact measurement. The laser reflection characteristics of C/SiC surface under high temperature were tested. The fiber Bragg grating sensor (FBG) sensor network measures both strain and temperature of the test piece, by means of wavelength shifts due to the tensile stress on a Bragg grating. The energy spectrum of the signal is obtained by the time–frequency analysis method, and the peak value is extracted by an algorithm to obtain the time–frequency characteristic of different modes. The result shows that the modal frequencies of C/SiC structure under time-varying thermal loads change with the temperature of the structure, which has a great influence on the modal characteristics of the structure. Besides, this study indicates that the FBG sensor is suitable for structural health monitoring of C/SiC structure under 1600 °C high temperature environment. The results provide an important basis for the dynamic performance analysis and safety design of structure under high-temperature thermal-vibration conditions.

Experimental investigation of semiconductor structures of the power source based on carbon-14

The article presents the research results of semiconductor silicon carbide (porous) structures with the implanted carbon-14. The results of experimental measurements collected data on parameters of photovoltaic energy conversion of light quanta into a photo-EMF to confirm the efficiency of p-n junction, an evaluation of the effectiveness of the introduction of carbon-14 in the molecule silicon carbide electrophysical measurements. In the process used the technology of solid-phase transformation of the surface of the monocrystalline silicon substrate in the phase of monocrystalline silicon carbide by chemical transport of carbon in the environment of hydrogen.

Pair distribution function analysis of neutron-irradiated silicon carbide

We have employed x-ray total scattering to investigate the structure of polycrystalline 3C-silicon carbide following neutron irradiation. The structure as a function of irradiation temperature and dose was quantified by analyzing pair distribution functions. Although the SiC matrix retains its crystal structure after irradiation, a significant increase in the diffuse scattering component is observable indicating that neutron irradiation leads to changes in both the short- and medium-range order. These changes include both an irradiation dose- and temperature-dependent increase in the vacancy concentration leading to an increase in the Si and C atomic displacement parameters. A dose-dependent decrease in the size of defect free material is also quantified from the structural refinements due to an increase in the number of defects and defect clusters. Evidence of additional correlations in the short-range order (up to ∼4 Å) from differential pair distribution function analysis indicate that combinations of atomistic defects including anti-site defects, vacancies and defect clusters are present after these irradiation conditions. Such structural information will be valuable for direct comparison of experimental and simulated atomic structures of irradiated silicon carbide.

Robocasting of reaction bonded silicon carbide structures

A novel shaping method for the fabrication of reaction bonded silicon carbide structures was investigated in this work. A paste consisting of silicon carbide as inert filler and carbon powder was developed and printed by robocasting technology. Layer by layer deposition of the ceramic paste facilitates the printing of complex shaped structures. Different structures such as lattices, hollow cylinders, bending bars and gyroids were printed using nozzles with diameter of 0.5 mm and 1.5 mm. After pyrolysis at 700 °C and further heat treatment at 1850 °C the samples were infiltrated using the liquid silicon infiltration technique to obtain dense near-net shape RBSC structures. The robocasted structures showed a hardness of approximately 20 GPa, a thermal conductivity of ∼112 W/m*K, Young’s modulus of ∼356 GPa, flexural strength of ∼224 MPa and an amount of residual silicon of approximately 23%. These measured properties are comparable with those of traditionally fabricated RBSC.

Computational fluid dynamic and thermal stress analysis of coatings for high‐temperature corrosion protection of aerospace gas turbine blades

AbstractThe current investigation presents detailed finite‐element simulations of coating stress analysis for a three‐dimensional, three‐layered model of a test sample representing a typical gas turbine component. Structural steel, titanium alloy, and silicon carbide are selected for main inner, middle, and outermost layers respectively. ANSYS is used to conduct three types of analysis—static structural, thermal stress analysis, and also computational fluid dynamic erosion (via ANSYS FLUENT). The specified geometry, which corresponds to corrosion test samples exactly, is discretized using a body‐sizing meshing approach, comprising mainly of tetrahedron cells. Refinements were concentrated at the connection points between the layers to shift the focus toward the static effects dissipated between them. A detailed grid independence study is conducted to confirm the accuracy of the selected mesh densities. The momentum and energy equations were solved, and the viscous heating option was applied to represent the improved thermal physics of heat transfer between the layers of the structures. A discrete phase model (DPM) in ANSYS FLUENT was used, which allows for the injection of continuous uniform air particles onto the model, thereby enabling an option for calculating the corrosion factor caused by hot air injection. Extensive visualization of results is provided. The simulations show that ceramic (silicon carbide) when combined with titanium clearly provide good thermal protection; however, the ceramic coating is susceptible to cracking and the titanium coating layer on its own achieves significant thermal resistance. Higher strains are computed for the two‐layer model than the single layer model (thermal case). However even with titanium only present as a coating the maximum equivalent elastic strain is still dangerously close to the lower edge. Only with the three‐layer combined ceramic and titanium coating model is the maximum equivalent strain pushed deeper towards the core central area. Here the desired effect of restricting high stresses to the strongest region of the gas turbine blade model is achieved, whereas in the other two models, lower strains are produced in the core central zones. Generally, the CFD analysis reveals that maximum erosion rates are confined to a local zone on the upper face of the three‐layer system which is in fact the sacrificial layer (ceramic coating). The titanium is not debonded or damaged which is essential for creating a buffer to the actual blade surface and mitigating penetrative corrosive effects. The present analysis may further be generalized to consider three‐dimensional blade geometries and corrosive chemical reaction effects encountered in gas turbine aero‐engines.

Design and fabrication of 10-kV silicon–carbide p-channel IGBTs with hexagonal cells and step space modulated junction termination extension**Project supported by the National Basic Research Program of China (Grant No. 2015CB759600), the Science Challenge Project, China (Grant No. TZ2018003), the National Natural Science Foundation of China (Grant Nos. 61474113, 61574140, and 61804149), the Beijing NOVA Program, China (Grant Nos. 2016071 and

10-kV 4H–SiC p-channel insulated gate bipolar transistors (IGBTs) are designed, fabricated, and characterized in this paper. The IGBTs have an active area of 2.25 mm2 with a die size of 3 mm × 3 mm. A step space modulated junction termination extension (SSM-JTE) structure is introduced and fabricated to improve the blocking performance of the IGBTs. The SiC p-channel IGBTs with SSM-JTE termination exhibit a leakage current of only 50 nA at −10 kV. To improve the on-state characteristics of SiC IGBTs, the hexagonal cell (H-cell) structure is designed and compared with the conventional interdigital cell (I-cell) structure. At an on-state current of 50 A/cm2, the voltage drops of I-cell IGBT and H-cell IGBT are 10.1 V and 8.3 V respectively. Meanwhile, on the assumption that the package power density is 300 W/cm2, the maximum permissible current densities of the I-cell IGBT and H-cell IGBT are determined to be 34.2 A/cm2 and 38.9 A/cm2 with forward voltage drops of 8.8 V and 7.8 V, respectively. The differential specific on-resistance of I-cell structure and H-cell structure IGBT are and , respectively. These results demonstrate that H-cell structure silicon carbide IGBT with SSM-JTE is a promising candidate for high power applications.

One-step ion beam irradiation manufacture of 3D micro/nanopatterned structures in SiC with tunable work functions

The fabrication and design of high-quality three-dimensional (3D) micro/nanostructures are of great importance for the development of new technology. Herein, we report a one-step technique to controllably manufacture 3D micro/nanopatterned structures with tunable work functions in silicon carbide (SiC). The multiscale micro/nanopatterned structures were produced directly by ion beam irradiation-induced swelling with the assistance of masks. The minimum feature size was ∼52 nm and the swelling height could be controlled flexibly from ∼1 to ∼250 nm. The change of work function of the 3D SiC micro/nanostructures could be tuned in the range between 0 and ∼126.6 meV. Distinct rectifying junction behavior was demonstrated between the irradiated and unirradiated zones. The Young's modulus and hardness values of the irradiated zones stabilized at ∼298.1 GPa and ∼24.9 GPa, respectively.

Spin–orbit coupling effects on the electronic structure of two-dimensional silicon carbide

Two-dimensional silicon carbide (2D-SiC) has attracted incredible research attention recently because of its wide bandgap and high exciton binding energy. Here, we focus on the effect of spin–orbit coupling (SOC) on its electronic structure through a detailed first-principles density functional theory study. The calculated electronic band structure and projected electron density of states indicate that Si 3p and C 2p electrons play a vital role in forming the electronic bandgap. The distribution of the real space charge density in the conduction and valence bands further confirms the electronic structure. It is found that inclusion of SOC causes splitting of both the valence and conduction bands. A wide SOC-induced bandgap of ~ 30 meV is observed in this novel material. Moreover, the effect of strain in modulating the bandgap and the SOC interaction is quantified. We find a linear reduction of both the normal and SOC-induced bandgap with increase of the biaxial tensile strain. Bandgap tuning based on such SOC effects may provide a pathway towards future optoelectronic and novel spintronic devices based on 2D-SiC.

Microstructural studies of core/rim structure of polycarbosilane-derived SiC consolidated by spark plasma sintering

Abstract Recently, attempts have been made to use silicon carbide (SiC) ceramics as a fuel compact in nuclear reactors. However, the use of sintering additives in the conventional sintering of SiC leads to a coarse microstructure with high porosity and large grains due to the low sinterability and the large amount of grain boundaries or a second phase, deteriorating the mechanical properties, and hence limiting widespread industrial applications. In this study, polycarbosilane (PCS) and spark plasma sintering (SPS) as the SiC precursor and sintering method, respectively, were applied to overcome the low sinterability and the use of sintering additives. As the raw material, amorphous PCS was prepared by pyrolysis at 1000 °C. To decrease the particle size, pyrolyzed PCS powder was subjected to ball milling by using high-energy ball milling. The ball-milled amorphous PCS powder was sintered by SPS. Sintering was carried out at different temperatures (i.e., 1700, 1800, and 1900 °C) and pressures (i.e., 40 and 80 MPa). After SPS, the core/rim structure of the sintered pellet was formed on account of the oxygen originating from the native oxide layer and free carbon in the PCS powder as the raw materials. In the core/rim structure comprising the core, as well as the intermediate and rim regions, the microstructure and chemistry of each region exhibited marginal difference with respect to the free carbon and oxygen. The phase fraction of α-SiC increased from the rim region to core region due to the discrepancy of actual loaded pressure on account of friction with the wall surface. The existing carbon was verified to be graphitized carbon. Owing to the short reaction time, graphitization did not completely proceed, and deficient graphitization led to graphitized carbon as not graphite. The introduced oxygen changed to amorphous SiO2, which was applied to the sintering-additive-like liquid-phase sintering.