Single Silicon Carbide Research Articles

High thermal insulation and high strength SiBCN@SiC double network ceramic composite aerogel

Silicon carbide (SiC) fiber materials prepared by precursor conversion method have attracted extensive attention in recent years due to their excellent high temperature resistance and thermal insulation properties. Herein, a novel SiBCN/SiC dual network ceramic composite aerogel with the three-dimensional (3D) porous SiC fiber network obtained by direct electrospinning as the first network and SiBCN aerogel as the second network was prepared by combining electrospinning with sol-gel technology and supercritical drying technology. The microstructure, phase composition, pore size distribution, compressive resistance, thermal insulation and related mechanisms of the 3D SiC fiber network and composite aerogel at different heat treatment temperatures were investigated in detail. The results show that the constructed double-network structure can make up for the heat transfer problem of a single SiC fiber network and further reduce its thermal conductivity, so that the prepared composite aerogel exhibits a lower thermal conductivity (∼0.0316 W m−1 K−1). In addition, the unique double network structure endows the composite aerogel with excellent compressive properties (2.56–2.89 MPa).

Design and optimization of a microneedle with skin insertion analysis for transdermal drug delivery applications

Effectively delivering the drugs through the human skin with less pain and reducing the chance of tissue damage are the main attributes of a microneedle. This paper presents an out-of-plane single silicon carbide (SiC) microneedle having six lumens for drug passing. The total length of the proposed microneedle is about 350 μm with the inner diameter of 30 μm and the outer diameter of 52 μm. COMSOL multiphysics software is used to analyze the performances of the proposed microneedle. The simulated durability of the microneedle is investigated by applying the axial load which generates less stress and deformation. Then, an optimized microneedle tip is designed which reduce pain during insertion. The flow analyses of various viscosity based fluids inside the microneedle are also investigated. Among the selected fluids, the flow of the ibuprofen shows a lowest velocity distribution because of its high dynamic viscosity. The maximum flow rates of ibuprofen are found as 0.01 μL/min and 0.9 μL/min while the inlet pressure are 10 kPa and 100 kPa respectively. On the contrary, a low viscosity fluid such as water provides flow rates of 45.24 μL/min and 433.49 μL/min at same inlet pressures. To verify the performances of our proposed microneedle, a skin model consisting three layers of stratum corneum, epidermis and dermis is designed. Simulation results confirm that the proposed microneedle successfully penetrated the skin model and remains unbroken.

Radiated disturbance characteristics of SiC MOSFET module

Wide band gap semiconductor device silicon carbide (SiC) metal oxide semiconductor field effect transistors (MOSFETs) have many advantages and are considered to be the most promising alternative to silicon (Si) insulated gate bipolar transistors (IGBTs) in low-/medium-voltage fields. However, a faster switching speed results in more serious electromagnetic disturbance problems in the application of SiC MOSFET. In this paper, an experiment system is established to measure the radiated disturbance of a single SiC MOSFET module operating at 9 kHz–300 MHz. The radiated electric fields of the SiC MOSFET module are mainly concentrated within 160 MHz. The switching voltage and radiated disturbance of the Si IGBT module are measured and compared with those of the SiC MOSFET module. The voltage of the SiC MOSFET has a faster change rate and a higher overshoot, which results in the radiated electric fields of SiC MOSFET module being 5–10 dB higher than those of the Si IGBT module below 8 MHz. The measurement results in the time-domain and frequency-domain correspond. A detailed model of a SiC MOSFET module is established and the radiated electric fields are calculated using the method of moments (MOM). The calculated results show the effectiveness of the model for radiated disturbance prediction. In this paper, the radiated electric fields of a SiC MOSFET module are measured and analyzed, and the calculation model can be used to further evaluate the radiated disturbance characteristics of SiC MOSFET and influencing factors.

Nuclear fragment identification with [formula omitted]E-E telescopes exploiting silicon carbide detectors

A study of the response of three ΔE-E telescopes to fragments produced in nuclear interactions at 40AMeV is presented. All the employed telescopes feature silicon carbide (SiC) detectors for at least one detection stage. Two identification methods have been used and their performance discussed: the ΔE-E technique and the Pulse Shape Analysis technique (for identification of nuclear fragments stopped in a single SiC layer). Identification capabilities similar to those obtained with the best available silicon detectors have been found for the SiC detector prototypes studied in this work.

An On‐Chip SiC MEMS Device with Integrated Heating, Sensing, and Microfluidic Cooling Systems

AbstractThere has been increasing interest in electronic systems with integrated microfluidic active cooling modules. However, the failure of 3C‐SiC/Si interface with increasing temperature has prevented the development of 3C‐SiC power electronic devices. Here, all integrated transparent heating, sensing, and cooling systems are developed on a single silicon carbide (SiC) chip for efficient thermal management. SiC nanofilms are grown on a silicon wafer, are transferred to a glass substrate, and then a micro electromechanical system process is employed to fabricate a SiC‐on‐glass system with integrated heaters and temperature sensors. A cooling system is fabricated with microchannel using 3D printing, molding, and plasma assisted bonding. The thermal management of the SiC‐based system shows an excellent capability of heating and detecting temperature as well as effective cooling with an efficiency of from 0.24 to 0.28 and a maximum cooling rate of 0.1 K(µL min−1)−1. The fabrication strategy can be utilized for large production of SiC power nanoelectronics with high efficiency of integrated thermal management systems.

Unintentionally Doped Epitaxial 3C-SiC(111) Nanothin Film as Material for Highly Sensitive Thermal Sensors at High Temperatures

There is a growing interest and demand to develop sensors that operate at high temperatures. In this work, we investigate the temperature sensing properties of unintentionally doped n-type single crystalline cubic silicon carbide (SiC) for high temperatures up to 800 K. A highly sensitive temperature sensor was demonstrated with a temperature coefficient of conductivity (TCC) ranging from ${1.96}\times {10}^{4}$ to ${5.18}\times {10}^{4}$ ppm/K. The application of this material was successfully demonstrated as a hot film flow sensor with its high signal-to-noise response to air flow at elevated temperatures. The high TCC of the single crystalline SiC film at and above 800 K strongly revealed its potential for highly sensitive thermal sensors working at high temperatures.

Heterojuncted non-metal binary composites silicon carbide/g-C3N4 with enhanced photocatalytic performance

Novel visible-light-driven silicon carbide (SiC)/g-C3N4 heterojuncted composites were successfully prepared via a facile ultrasonic dispersion and calcination method, and afterwards characterized by a couple of technologies including XRD, SEM, TEM, FT-IR, XPS, UV–vis DRS, PL spectra, and N2 adsorption-desorption. It was found that SiC nanoparticles were uniformly deposited over the surface of g-C3N4 to create heterojunction domains along phase interface boundary, favoring charge carriers transfer and separation across the straddling band alignments. Besides, the visible-light absorption capability of samples was enhanced by the incorporation of SiC. These physiochemical merits ensured the improved photocatalytic performance of heterojuncted composites over the degradation of dyes rhodamine B (RhB) and methyl orange (MO) in comparison to each single component SiC or g-C3N4. Upon an identical condition, the sample SN8 exhibited the highest photocatalytic ability among all tested samples. According to active species trapping measurements, ∙OH and ∙O2- were deemed as major radicals and eventually a possible photocatalysis mechanism was speculated.

Surface Metallization of Silicon Carbide By Electroless Deposition

Silicon carbide (SiC) is one of the most promising semiconductor materials for a next generation of power devices. Its physical properties such as breakdown electric field and thermal conductivity are higher and more suitable for efficient power devices than those of silicon, which is common semiconductor material for the present devices. The metallization of SiC surfaces is a key technology to use SiC for power devices. The autocatalytic electroless deposition, which is a conventional method to metallize non-conductive substrates, has several advantages, however, cannot produce adhesive metal films directly on SiC. We recently developed a new surface-activation process for the direct electroless deposition of adhesive metal films on silicon substrates (1, 2). This process uses gold (Au) nanoparticles epitacially grown on silicon by an electroless displacement deposition (3, 4). In this study, this process is applied for formation of adhesive metal films on SiC. The single crystalline n-type 4H-SiC (0001) wafers were used as the substrates. Au nanoparticles were deposited on SiC substrates using a HAuCl4 solution containing HF or KOH under photoillumination using a Hg-Xe short arc lamp. Then, nickel-phosphorus alloy (Ni-P) films were electrolessly formed on the SiC substrates by using NiSO4 solution containing NaPH2O2as a reducing agent. The adhesion of the electrolessly deposited Ni-P films on SiC substrates was examined by a tape test based on Japanese Industrial Standard JIS H8504 corresponding to ISO 2819. Figure 1 shows SEM images of Au-nanoparticle-deposited SiC substrates. The size and particle density of Au deposited using the solution containing KOH (Fig. 1 (b)) were larger than that using HF (Fig.1 (a)). The surface of SiC substrates was roughened by the electroless deposition of Au nanoparticles. No photoillumination significantly attenuated the Au deposition. These results indicate that this Au nanoparticle deposition is a photoelectrochemical displacement reaction. The autocatalytic electroless deposition of Ni-P films was initiated on the Au-nanoparticle-deposited SiC substrate. No deposition occurred on a bare SiC substrate. The adhesion of metal films formed on the SiC substrates depended on the deposition time of Au nanoparticles. Immersion of SiC substrates in the Au-deposition solution containing KOH for 15 min obtained high adhesion. No peeling occurred up to 1.3 μm in thickness of Ni-P films by the tape test. This result is similar to that in the case of single crystalline silicon substrates (1 - 4). In conclusion, we successfully formed adhesive metal films directly on single crystalline SiC substrates by using wet processes that are electroless displacement deposition of Au nanoparticles and common autocatalytic electroless deposition of Ni-P alloy films. Acknowledgements The present work was partly supported by KAKENHI (26289276) from JSPS and A-STEP from JST. References 1) S. Yae, M. Enomoto, H. Atsushiba, A. Hasegawa,N. Fukumuro, S. Sakamoto, and H. Matsuda., ECS Trans., 53 (6), 99 (2013). 2) H. Atsushiba, Y. Orita, S. Sakamoto, N. Fukumuro, and S. Yae., ECS Trans., 61(10), 9 (2014). 3) N. Yamada, H. Atsushiba, S. Sakamoto, N. Fukumuro, and S. Yae., ECS Trans., 69(39), 59 (2015).4) N. Yamada, S. Sakamoto, N. Fukumuro, and S. Yae., Symposium Z01 in this meeting (2016). Figure 1

Amorphization resistance of nano-engineered SiC under heavy ion irradiation

Silicon carbide (SiC) with a high-density of planar defects (hereafter, ‘nano-engineered SiC’) and epitaxially-grown single-crystalline 3C-SiC were simultaneously irradiated with Au ions at room temperature, in order to compare their relative resistance to radiation-induced amorphization. It was found that the local threshold dose for amorphization is comparable for both samples under 2 MeV Au ion irradiation; whereas, nano-engineered SiC exhibits slightly greater radiation tolerance than single crystalline SiC under 10 MeV Au irradiation. Under 10 MeV Au ion irradiation, the dose for amorphization increased by about a factor of two in both nano-engineered and single crystal SiC due to the local increase in electronic energy loss that enhanced dynamic recovery.

Effect of fiber content on single tow SiC minicomposite mechanical and damage properties using acoustic emission

Ceramic matrix composites (CMCs) are attractive materials for use in temperature-critical aerospace and nuclear applications. Relating the mechanical behavior and damage mechanisms of simple ceramic matrix minicomposites to health-monitoring techniques helps to understand the fundamentals of the mechanical response of CMCs. In this study, single-tow minicomposites with a silicon carbide (SiC) matrix deposited by chemical vapor infiltration, a boron nitride or a carbon interphase, and various types of SiC fibers were tested in tension at room temperature. Modal acoustic emission (AE) was used to determine the dependence of matrix cracking on the applied load. Crack density evolution was obtained using two AE-based methods: the established method using cumulative energy of AE events and a new technique based on speed of sound measurements.

Fabrication and characterization of single-crystal 4H-SiC microactuators for MHz frequency operation and determination of Young’s modulus

Silicon carbide (SiC), a wide bandgap semiconductor, is more desirable over conventional silicon (Si) to satisfy the increasing demands for microelectromechanical system (MEMS) to operate in harsh environments due to the excellent physical, mechanical and chemical inertness. Research in MEMS devices based on single or polycrystalline SiC on Si or SOI substrate, such as 3C-SiC polytype, have been widely carried out. Another promising candidate is “all”-SiC, i.e., homoepitaxial single crystal SiC layer on single-crystal SiC substrate, such as 4H and 6H-SiC polytypes. They truly exploit the superior material properties of SiC and provide advantages for MEMS devices to operate in hostile conditions. In this work, 4H-SiC MEMS actuators in cantilever and bridge configurations were fabricated by a surface micromachining process, and their dynamic responses were characterized to determine Young’s modulus of 4H-SiC and frequency performance. Resonant frequencies of 1.208MHz from cantilever and 1.338MHz from bridge actuators were achieved. These high frequency operation capabilities are particular interesting for ultrafast and high resolution sensors and actuators.

Theoretical Maximum Efficiency for a Linearly Graded Alphavoltaic Nuclear Battery

This paper presents a study on the optimization of the amount of energy deposited by alpha particles in the depletion region of a silicon carbide (SiC) alphavoltaic cell using Monte Carlo models. Three Monte Carlo codes were used in this study: SRIM/TRIM, GEANT4, and MCNPX. The models examined the transport of 5.307-MeV alpha particles emitted by 210Po. Energy deposition in a 1-μm depletion region of SiC was calculated using an isotropic alpha source for a spherical geometry using GEANT4, and a monodirectional alpha source for a slab geometry using both SRIM/TRIM and GEANT4. In addition, an isotropic point source was modeled using GEANT4 and MCNPX for a slab geometry. These geometries were optimized for the maximum possible alphavoltaic energy efficiency. The models, which match very well, indicate that the maximum theoretical energy conversion efficiency, which was optimized for a SiC alphavoltaic cell, is [approximately]3.6% for the isotropic alpha source on a slab geometry and 2.1% for both the monodirectional alpha source on a slab geometry and the isotropic alpha source at the center of a sphere. This study provides a useful guide governing the upper limit of expected efficiency for an alphavoltaic cell using a linearly graded single junction SiC transducer.

Silicon carbide-based photonic crystal nanocavities for ultra-broadband operation from infrared to visible wavelengths

To realize nanophotonic devices that operate in both the infrared and visible wavelength ranges on a single wafer, we investigated the optical characteristics of silicon carbide (SiC)-based photonic crystal nanocavities. By fabricating nanocavities with lattice constants ranging from 150 to 600 nm, we experimentally demonstrated resonant wavelengths of individual cavities ranging from 550 to 1450 nm on a single SiC wafer. Furthermore, this ultra-broadband operation reveals the material dispersion of the thin SiC wafer, which is estimated as nSiC = 2.34 + 9.18 × 104/λ2, over the wide range of aforementioned wavelengths.

Second-harmonic generation and linear electro-optical coefficients of SiC polytypes and nanotubes

The second-order nonlinear optical susceptibility $[{\ensuremath{\chi}}_{abc}^{(2)}]$ and linear electro-optical coefficient $({r}_{abc})$ of a large number of single-walled zigzag, armchair, and chiral silicon carbide (SiC) nanotubes (SiC NTs), as well as bulk SiC polytypes (2H-, 4H-, 6H-, and 3C-SiC) and single graphitic SiC sheet have been calculated from the first principles. The calculations are based on the density-functional theory in the local-density approximation where the highly accurate full-potential projector augmented-wave method was used. Both the zigzag and chiral SiC NTs are found to exhibit large second-order nonlinear optical behaviors with the ${\ensuremath{\chi}}_{abc}^{(2)}$ and ${r}_{abc}$ coefficients being up to ten times larger than that of bulk SiC polytypes and also being up to thirteen times larger than the counterparts of the corresponding BN NTs, indicating that SiC NTs are promising materials for nonlinear optical and optoelectric applications. The features in the spectra of ${\ensuremath{\chi}}_{abc}^{(2)}(\ensuremath{-}2\ensuremath{\omega},\ensuremath{\omega},\ensuremath{\omega})$ of the SiC NTs are discussed in terms of the single- and two-photon resonances and also related to the features in the linear dielectric function $\ensuremath{\epsilon}(\ensuremath{\omega})$.

Presolar He and Ne Isotopes in Single Circumstellar SiC Grains

Noble gas isotopes in presolar silicon carbide (SiC) dust grains from primitive meteorites provide, together with major element isotopic compositions, insight into the nucleosynthetic output of different types of evolved stars >4.5 Gyr ago. We report here new results from helium and neon isotopic analyses of single presolar SiC grains with sizes between 0.6 and 6.3 μm using an ultrahigh sensitivity mass spectrometer. These noble gas studies were complemented by an ion microprobe study (NanoSIMS) of Si, C, and N isotopic compositions of the same grains. About 40%, or 46 of the 110 grains analyzed, contain nucleosynthetic 22Ne and/or 4He from their parent stars above our mass spectrometer's detection limit. We discuss the possible stellar sources using isotopic ratios as constraints combined with new model predictions for low- to intermediate-mass (1.5, 2, 3, and 5 M☉) asymptotic giant branch (AGB) stars of different metallicities (1, 1/2, 1/3, and 1/6 Z☉). Most SiC grains are of the mainstream type and originated in low-mass AGB stars. We find a higher-than-expected percentage of A/B type grains, with some containing 22Ne and/or 4He. In addition, we find one noble gas-rich nova grain candidate, one supernova grain (X-type grain), and one 22Ne-rich X- or Z-type grain candidate.

Mechanical Properties of 3C-SiC Films for MEMS Applications

AbstractThere is a technological need for hard thin films with high elastic modulus and fracture toughness. Silicon carbide (SiC) fulfills such requirements for a variety of applications at high temperatures and for high-wear MEMS. A detailed study of the mechanical properties of single crystal and polycrystalline 3C-SiC films grown on Si substrates was performed by means of nanoindentation using a Berkovich diamond tip. The thickness of both the single and polycrystalline SiC films was around 1-2 μm. Under indentation loads below 500 μN both films exhibit Hertzian elastic contact without plastic deformation. The polycrystalline SiC films have an elastic modulus of 457 GPa and hardness of 33.5 GPa, while the single crystalline SiC films elastic modulus and hardness were measured to be 433 GPa and 31.2 GPa, respectively. These results indicate that polycrystalline SiC thin films are more attractive for MEMS applications when compared with the single crystal 3C-SiC, which is promising since growing single crystal 3C-SiC films is more challenging.

Si–C multilayer quasi crystals preparation by DC magnetron sputtering

Silicon carbide (SiC) is becoming one of the most important electronic materials in recent years. Single crystalline SiC is a wide-bandgap semiconductor, which finds a wide range of applications in high temperature, power consuming, and fast-acting electron devices. Common methods applied for silicon carbide films deposition are: plasma-enhanced CVD under plasma decomposition of organic compounds such as CH4, C2H2, C3H8. These methods are complicated and expensive.In this work we grew silicon–carbon films as Si–C thin film multilayer system with successive layers of Si and C both of equal thicknesses. The Si–C systems grown in our experiments consisted of 40 sub-layers, deposited by DC magnetron sputtering on silicon, on glass, and on Au substrates in argon plasma environment. Sputtering was provided continuously from two targets: graphite and single-crystalline silicon. Optical and electro-physical properties of the deposited thin film systems were investigated. Relative permittivity of the grown thin film systems was found to be the main and most important parameter of the Si–C system.

PECVD SiC optical waveguide loss and mode characteristics

We report the fabrication of single mode SiC (silicon carbide) waveguides and the measurement of their propagation loss. By studying the effect of sidewalls scattering loss due to surface roughness and by reducing it, minimal propagation loss of 2.3 dB/cm for the TM polarization is measured in the visible at 0.633 μm. This loss can be used as a benchmark for further development of SiC microphotonic components and circuit for sensor systems in harsh environment.

Micropipe healing in SiC wafers by liquid-phase epitaxy in Si–Ge melts

Liquid-phase epitaxy (LPE) of silicon carbide (SiC) was shown to be an effective technique to overgrow micropipe defects (MP) in SiC wafers prepared by the physical vapour transport (PVT) technique. Growth close to thermodynamic equilibrium, e.g. low supersaturation, provides a favourable condition for effective MP healing. Therefore, the aim of this work was to grow epitaxial layers from strongly diluted Si-based solutions. Using the method of horizontal dipping, the dependence of MP elimination efficiency on Si–Ge flux composition and on the crystallographic orientation (on- and off-axis) of the SiC wafer was investigated. High-quality single crystalline SiC layers of a thickness up to 10μm were grown with the growth rate of 0.5μm/h. On off-oriented wafers, stepped growth morphology was observed independent of the melt composition. Micropipes with the diameter below 5 μm were closed with an efficiency of about 80%. SEM investigations as well as inspection under reflected/transmitted light did not show any specific distortion of the growth morphology at the micropipe healing place.

Preparation of Silicon Carbide Nano-Particles Using a Pulsed Laser Deposition Method

AbstractWe have developed a new pulsed laser deposition technique using two Nd:YAG laser beams for the nucleation of silicon carbide (SiC) crystalline nano-particles and single crystalline SiC thin films. Transmission electron microscopy and atomic force microscopy observation suggest that several nanometer size SiC particles can be prepared by the new pulsed laser deposition (PLD) method using two Nd:YAG laser beams (1064nm and 532nm). X ray photoelectron spectroscopy measurements suggest that the silicon/carbon composition ratio of the prepared SiC thin films can be controlled by laser fluence and wavelength.