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Dielectric properties of porous SiC/Si3N4 ceramics by polysilazane immersion-pyrolysis
摘要： The SiC nanotubes were synthesized on porous Si3N4 matrix by polysilazane immersion-pyrolysis. The β-SiC and free C contents increased with the increasing dipping times, which cause some clear vibration and loss peaks of the dielectric constant patterns emerged at around 12.9 GHz and 14.7 GHz in the samples of 20 wt% and 30 wt% benzoic acid, respectively. The re?ectivity of the obtained ceramics were ?7dB ～ ?10dB from the frequency of 8 GHz–18 GHz, which means that the amount of 80%–90% electromagnetic wave could be attenuated. The ceramics containing 40 wt% benzoic acid showed the high loss, low re?ectivity and a wide absorbing band, indicating the high absorbing e?ciency and good dielectric properties.
关键词： Dielectric properties,Si3N4,Dipping,SiC
更新于2025-11-21 11:18:25
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G‐C3N4‐SiC‐Pt for Enhanced Photocatalytic H2 Production from Water under Visible Light Irradiation
摘要： The g-C3N4 and SiC has drawn increasing attention for application to visible light photocatalytic hydrogen evolution from water splitting due to their unique band structure and high physicochemical stability. In this study, g-C3N4-SiC heterojunction with loaded noble metal was constructed. The g-C3N4-SiC-Pt composite photocatalysts were successfully prepared by the combination method of a bio-reduction, sol-deposition and calcination. The layers of g-C3N4 were thinned and the SiC and Pt nanoparticles simultaneously were tightly bound to g-C3N4 by calcination in the process of preparing the g-C3N4-SiC-Pt. The heterojunction formed in the interface of SiC and g-C3N4 enhances the separation efficiency of the photogenerated electron-hole pairs. These composite photocatalysts achieve a high hydrogen evolution rate of 595.3 μmol·h-1·g-1 with a 1wt% of deposited Pt, 3.7- and 2.07-fold higher than g-C3N4-bulk and g-C3N4-SiC under visible-light irradiation with a quantum efficiency of 2.76% at 420 nm, respectively.
关键词： visible light,g-C3N4-SiC-Pt photocatalysts,hydrogen evolution,photocatalysis
更新于2025-11-21 11:01:37
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Electrical characterization of high k-dielectrics for 4H-SiC MIS devices
摘要： We report promising results regarding the possible use of AlN or Al2O3 as a gate dielectric in 4H-SiC MISFETs. The crystalline AlN ?lms are grown by hot wall metal organic chemical vapor deposition (MOCVD) at 1100 °C. The amorphous Al2O3 ?lms are grown by repeated deposition and subsequent low temperature (200 °C) oxidation of thin Al layers using a hot plate. Our investigation shows a very low density of interface traps at the AlN/4H-SiC and the Al2O3/4H-SiC interface estimated from capacitance-voltage (CV) analysis of MIS capacitors. Current-voltage (IV) analysis shows that the breakdown electric ?eld across the AlN or Al2O3 is ～ 3 MV/cm or ～ 5 MV/cm respectively. By depositing an additional SiO2 layer by plasma enhanced chemical vapor deposition at 300 °C on top of the AlN or Al2O3 layers, it is possible to increase the breakdown voltage of the MIS capacitors signi?cantly without having pronounced impact on the quality of the AlN/SiC or Al2O3/SiC interfaces.
关键词： MIS structure,Interface traps,Al2O3/4H-SiC interface,AlN/4H-SiC interface
更新于2025-11-14 17:28:48
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Thickness of sublimation grown SiC layers measured by scanning Raman spectroscopy
摘要： We have grown homoepitaxial high resistivity SiC layers on conducting SiC substrates. We develop a method to determine the thickness of grown layers by scanning confocal Raman spectroscopy (SCRS). We also grow epitaxial graphene on SiC layers to label the top sample surface, and, we correlate the top surface position with Rayleigh scattering (RS). The interface between the high resistivity SiC layer and conductive SiC substrate is probed by the transition from LO phonon to the coupled LO phonon-plasmon Raman mode. The layer thickness measurements are veri?ed by ellipsometry and Secondary Ion Mass Spectroscopy (SIMS). We show that the SCRS method provides superior lateral and vertical resolution, it is robust against errorneous conclusions based on ad-hoc models, and it is easy to implement.
关键词： SiC layer thickness,Graphene,Raman spectroscopy
更新于2025-11-14 15:19:41
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An Improved Proposed Single Phase Transformerless Inverter with Leakage Current Elimination and Reactive Power Capability for PV Systems Application
摘要： Single-phase transformerless inverters are broadly studied in literature for residential-scale PV applications due to their great advantages in reducing system weight, cost and elevating system efficiency. The design of transformerless inverters is based on the galvanic isolation method to eliminate the generation of leakage current. Unfortunately, the use of the galvanic isolation method alone cannot achieve constant common mode voltage (CMV). Therefore, a complete elimination of leakage current cannot be achieved. In addition, modulation techniques of single-phase transformerless inverters are designed for the application of the unity power factor. Indeed, next-generation PV systems are required to support reactive power to enable connectivity to the utility grid. In this paper, a proposed single-phase transformerless inverter is modified with the clamping method to achieve constant CMV during all inverter operating modes. Furthermore, the modulation technique is modified by creating a new current path in the negative power region. As a result, a bidirectional current path is created in the negative power region to achieve reactive power generation. The simulation results show that the CMV is completely clamped at half the DC link voltage and the leakage current is almost completely eliminated. Furthermore, a reactive power generation is achieved with the modified modulation techniques. Additionally, the total harmonic distortion (THD) of the grid current with the conventional and a modified modulation technique is analyzed. The efficiency of the system is enhanced by using wide-bandgap (WBG) switching devices such as SiC MOSFET. It is observed that the efficiency of the system decreased with reactive power generation due to the bidirectional current path, which leads to increasing conduction losses.
关键词： leakage current,transformerless inverter,reactive power,wide-bandgap (WBG),silicon carbide (SiC),photovoltaic (PV) power system
更新于2025-09-23 15:23:52
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Atomic-scale simulations of ideal strength and deformation mechanism in β-SiC under H/He irradiation
摘要： We ?rstly investigated the mechanical responses of β-SiC to the tensile and shear strains under H/He irradiation using density functional theory, with a speci?c focus on the atomistic mechanism of deformation and fracture. The results revealed that the e?ect of introducing H/He on ideal strengths of tension and shear is limited, due to the strong sp3 bonds of Si-C. However, somehow large disparity in failure was discovered after introducing H/He. Under the tension, all Si-C bonds along the tensile direction are synchronously broken, causing cubic-to-graphitic transformation in the perfect β-SiC, in contrast to the asynchronous breakage of Si-C bonds in the H/He-doping systems. Under the shear, H- and He-doping systems display individual cleavage-like modes of lattice instability, respectively, whereas structural transformation by re-bonding new Si-C bonds is responsible for the failure in the perfect β-SiC. The cleavage-like modes were discussed, combining a detailed analysis of electronic structure. The mechanical response to H/He irradiation distinguishes β-SiC from conventional metals presently applied in nuclear industry. The study may provide a clue for new design strategy of irradiation-tolerant materials for energy applications.
关键词： Ideal strength,H/He irradiation,Deformation mechanism,β-SiC ceramic
更新于2025-09-23 15:23:52
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Acceptor levels of the carbon vacancy in 4 <i>H</i> -SiC: Combining Laplace deep level transient spectroscopy with density functional modeling
摘要： We provide direct evidence that the broad Z1/2 peak, commonly observed by conventional deep level transient spectroscopy in as-grown and at high concentrations in radiation damaged 4H-SiC, has two components, namely, Z1 and Z2, with activation energies for electron emissions of 0.59 and 0.67 eV, respectively. We assign these components to Z?1/2 + e? → Z?1/2 → Z?1/2 + 2e? transition sequences from negative-U ordered acceptor levels of carbon vacancy (V_C) defects at hexagonal/pseudo-cubic sites, respectively. By employing short filling pulses at lower temperatures, we were able to characterize the first acceptor level of V_C on both sub-lattice sites. Activation energies for electron emission of 0.48 and 0.41 eV were determined for Z1(?/0) and Z2(?/0) transitions, respectively. Based on trap filling kinetics and capture barrier calculations, we investigated the two-step transitions from neutral to doubly negatively charged Z1 and Z2. Positions of the first and second acceptor levels of V_C at both lattice sites, as well as (?/0) occupancy levels, were derived from the analysis of the emission and capture data.
关键词： density functional theory,acceptor levels,deep level transient spectroscopy,negative-U ordering,carbon vacancy,4H-SiC
更新于2025-09-23 15:23:52
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A novel SiC nanowire aerogel consisted of ultra long SiC nanowires
摘要： SiC nanowire aerogel (SNA) with highly porous 3D nanowire architecture was synthesized by polymer pyrolysis chemical vapor deposition (PPCVD) process to deposit SiC nanowires in the pores of carbon foam, followed by high temperature oxidation of carbon foam. The microstructure of the prepared SNA was characterized by SEM, TEM and a large number of interweaving SiC nanowires with a diameter of 80-100 nm and a length of hundreds of micrometers form the highly porous 3D nanowire architecture of SNA. The prepared SNA possesses the performance combination of ultra-low density (30±7 mg·cm-3), high-temperature oxidation resistance (750 °C), noncombustible and fire resistance property in the fire, excellent thermal insulating property (0.03 W·m-1·k-1 at room temperature in He) and compressive strength of 0.11 MPa, which is applicable as high-temperature heat insulator, ceramic matrix composite, high temperature flue gas filter, fire-proofing material and catalyst carrier.
关键词： Carbon foam,Aerogel,SiC nanowire,CVD
更新于2025-09-23 15:23:52
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Silicon carbide nanowire field effect transistors with high on/off current ratio
摘要： We report the important performance parameters of SiC-NWFET devices including on/off current ratio (Ion/Ioff), gating effect, transconductance (gm), and carrier mobility (μh). The channel length dependence of these key performance parameters of the SiC-NWFETs with varying channel lengths ranging from 120 nm to 1.5 μm has been demonstrated. The device with the 120 nm channel length has led to a very high on/off current ratio (1.34 × 10^4) and very strong gating effect. Furthermore, the transconductance and the hole mobility have been determined as 6.9 nS and 1.696 cm2/V·s, respectively, at Vds of 0.05 V. This study shows good promise of the SiC-NWFET devices to be used in advanced solid-state nanoelectronic devices capable of operating at high frequency and high temperature.
关键词： On/off current ratio,Transconductance,Gating effect,SiC-NWFETs
更新于2025-09-23 15:23:52
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The 1.2 kV 4H-SiC OCTFET: A New Cell Topology with Improved High Frequency Figures-of-Merit
摘要： A 1.2 kV rated 4H-SiC OCTFET device with octagonal-cell topology is proposed and experimentally demonstrated for the first time. The device was first optimized using TCAD numerical simulations. Devices were then successfully fabricated in a 6 inch foundry. From the measured electrical characteristics, the OCTFET is demonstrated to have 1.4× superior HF-FOM [Ron×Qgd], and 2.1× superior HF-FOM [Ron×Cgd] compared with the conventional linear-cell MOSFET.
关键词： Silicon carbide,ALL,Octagonal,Qgd,HF-FOMs,Cell,Cgd,MOSFET,4H-SiC
更新于2025-09-23 15:23:52