Single Crystal 3C-SiC Research Articles

Pseudo-Hall Effect in Single Crystal n-Type 3C-SiC(100) Thin Film

This article reports the first results on stress induced pseudo-Hall effect in single crystal n-type 3C-SiC(100) grown by LPCVD process. After the growth process, Hall devices were fabricated by standard photolithography and dry etching processes. The bending beam method was employed to study the stress induced changes in the electrical response of the fabricated Hall devices. It has been observed that when stress is applied to the 3C-SiC(100) Hall devices, the offset voltage of the Hall devices varies linearly with the applied compressive and tensile stresses which is called, the pseudo-Hall effect. The variation of the offset voltage of these Hall devices is also proportional to the applied input current. This variation of the offset voltage with the applied compressive and tensile stresses shows that single crystal n-type 3C-SiC(100) can be used for stress sensing applications.

Fundamental piezo-Hall coefficients of single crystal p-type 3C-SiC for arbitrary crystallographic orientation

Piezo-Hall effect in a single crystal p-type 3C-SiC, grown by LPCVD process, has been characterized for various crystallographic orientations. The quantified values of the piezo-Hall effect in heavily doped p-type 3C-SiC(100) and 3C-SiC(111) for different crystallographic orientations were used to obtain the fundamental piezo-Hall coefficients, P12=(5.3±0.4)×10-11 Pa-1,P11=(−2.6±0.6)×10-11 Pa-1, and P44=(11.42±0.6)×10-11 Pa-1. Unlike the piezoresistive effect, the piezo-Hall effect for (100) and (111) planes is found to be independent of the angle of rotation of the device within the crystal plane. The values of fundamental piezo-Hall coefficients obtained in this study can be used to predict the piezo-Hall coefficients in any crystal orientation which is very important for designing of 3C-SiC Hall sensors to minimize the piezo-Hall effect for stable magnetic field sensitivity.

Atomic-scale characterization of occurring phenomena during hot nanometric cutting of single crystal 3C–SiC

Nanometric cutting of single crystal 3C–SiC on the three principal crystal orientations at various cutting temperatures spanning from 300 K to 3000 K was investigated by the use of molecular dynamics (MD) simulation.

3D-branched hierarchical 3C-SiC/ZnO heterostructures for high-performance photodetectors.

The ultra-sensitive photodetection of different wavelengths holds promising applications in high-performance optoelectronic devices and it requires an efficient and suitable semiconductor unit. Herein, we demonstrated the designable synthesis of 3D-branched hierarchical 3C-SiC/ZnO heterostructures by a three-step process and their assembling into an ultrasensitive photodetector. Microstructure analyses using high-resolution transmission electron microscopy reveal that the hierarchical 3C-SiC/ZnO heterostructure is composed of single-crystal 3C-SiC nanowires as a central stem and numerous well-aligned single-crystalline ZnO nanorods as branch shells. Optoelectronic tests on the 3C-SiC/ZnO heterostructure photodetector verify the outstanding photo-detection performance with an ultrahigh EQE (1.69 × 108%), a superior photoresponsivity (4.8 × 105 A W-1), a very fast response time (a rise time of 40 ms and a decay time of 60 ms), a high photo-dark current ratio of 187.8 and an excellent photocurrent stability and reproducibility, which is significantly advantageous or comparable to those of ZnO and other inorganic semiconductor nanostructure based photodetectors. To understand the excellent photodetection of hierarchical 3C-SiC/ZnO heterostructures, a band-gap energy diagram describing the photogenerated electron transport process is plotted and the corresponding mechanism is discussed. The strategy proposed in the present work will open up more opportunities for the design and boost of ultra-sensitive photodetectors based on semiconductor heterostructures.

Grain growth of nanocrystalline 3C-SiC under Au ion irradiation at elevated temperatures

Nanocrystalline silicon carbide (SiC) represents an excellent model system for a fundamental study of interfacial (grain boundary) processes under nuclear radiation, which are critical to the understanding of the response of nanostructured materials to high-dose irradiation. This study reports on a comparison of irradiation effects in cubic phase SiC (3C-SiC) grains of a few nanometres in size and single-crystal 3C-SiC films under identical Au ion irradiation to a range of doses at 700 K. In contrast to the latter, in which the lattice disorder is accumulated to a saturation level without full amorphization, the average grain size of the former increases with dose following a power-law trend. In addition to coalescence, the grain grows through atomic jumps and mass transport, where irradiation-induced vacancies at grain boundaries assist the processes. It is found that a higher irradiation temperature leads to slower grain growth and a faster approach to a saturation size of SiC nanograins. This unusual behaviour could be associated with irradiation-induced grain nucleation and growth in amorphous SiC matrix in which the 3C-SiC grains are embedded. The results could potentially have a positive impact on structural components of advanced nuclear energy systems.

Molecular dynamics simulation study of deformation mechanisms in 3C–SiC during nanometric cutting at elevated temperatures

Molecular dynamics (MD) simulation was employed in this study to elucidate the dislocation/amorphization-based plasticity mechanisms in single crystal 3C–SiC during nanometric cutting on different crystallographic orientations across a range of cutting temperatures, 300K to 3000K, using two sorts of interatomic potentials namely analytical bond order potential (ABOP) and Tersoff potential. Of particular interesting finding while cutting the (110)<001̅> was the formation and subsequent annihilation of stacking fault-couple and Lomer–Cottrell (L–C) lock at high temperatures, i.e. 2000K and 3000K, and generation of the cross-junctions between pairs of counter stacking faults meditated by the gliding of Shockley partials at 3000K. Another point of interest was the directional dependency of the mode of nanoscale plasticity, i.e. while dislocation nucleation and stacking fault formation were observed to be dominant during cutting the (110)<001̅>, low defect activity was witnessed for the (010)<100> and (111)<1̅10> crystal setups. Nonetheless, the initial response of 3C–SiC substrate was found to be solid-state amorphization for all the studied cases. Further analysis through virtual X-ray diffraction (XRD) and radial distribution function (RDF) showed the crystal quality and structural changes of the substrate during nanometric cutting. A key observation was that the von Mises stress to cause yielding was reduced by 49% on the (110) crystal plane at 3000K compared to what it took to cut at 300K. The simulation results were supplemented by additional calculations of mechanical properties, generalized stacking faults energy (GSFE) surfaces and ideal shear stresses for the two main slip systems of 3C–SiC given by the employed interatomic potentials.

Feasibility of terahertz generation and detection in 3C-SiC single crystal

We theoretically investigate the feasibility of terahertz generation and detection in a 〈110〉-oriented 3C-SiC single crystal excited by a frequency-doubled Yb-doped femtosecond pulse laser. The phase-matching condition of optical rectification (OR) and electro-optic (EO) sampling are analyzed on the basis of the dispersion relation of 3C-SiC. The THz generation bandwidth as well as the peak frequency position via OR are calculated at different crystal thicknesses. The THz detection bandwidth on EO sampling is discussed on the basis of 2 different schemes. In the collinear incidence scheme, the cut-off frequency as a function of crystal thickness is revealed. In the noncollinear incidence scheme, the phase-matching condition can be achieved locally by using a silicon prism to couple the THz radiation into a 3C-SiC single crystal. The relationship between THz coherence length and the apex angle of the Si prism is discussed. The detection sensitivity of 3C-SiC at the wavelength of an Yb-doped femtosecond pulse laser is compared with those of other zinc blende EO crystals, which is found to be higher than that of GaP but lower than those of GaAs and ZnTe. Considering the optimal phase-matching condition at a wavelength of 515 nm, 3C-SiC is found to be a potential EO crystal for THz generation and detection using a frequency-doubled Yb-doped femtosecond laser.

3C-SiC Crystal on Sapphire by Solution Growth Method

We realized the growth of 3C-SiC crystal on sapphire by solution growth method. The carbon deposition on a sapphire substrate before growth is the key point for this technology. This carbon layer plays a role to protect the dissolution of sapphire by Si solvent. Single crystal of 3C-SiC was grown on the whole surface of the sapphire substrate. Surprisingly, the 3C-SiC layer did not directly grown on the sapphire substrate. The single crystal 3C-SiC layer formed by the reaction between the deposited carbon and the Si wafer that is a solvent material below the melting point of silicon during heating process before the growth. The 3C-SiC grew on the 3C-SiC layer. In this process, the deposited carbon play another important role.

Hetero-Epitaxial Single Crystal 3C-SiC Opto-Mechanical Pressure Sensor

The design, fabrication, early testing and material property assessment work related to the development of an opto-mechanical pressure sensor implemented with hetero-epitaxial 3C-SiC on silicon is described. The sensor is constituted by a single-crystal 3C-SiC membrane whose deflection upon pressure application is measured using a fiber-optic interferometric readout. The fabrication of sensor prototypes and micromachined 3C-SiC membranes for test purposes is described and the results of bulge tests on the membranes are reported. Functional characterization of the sensor prototypes in the pressure range 0-3 bar is also presented, showing good linearity and reproducibility of the sensor response, sensitivity of roughly 2 mV/bar and estimated pressure resolution around 0.5 bar on a 0-200 bar dynamic range.

Observations of Ag diffusion in ion implanted SiC

The nature and magnitude of Ag diffusion in SiC has been a topic of interest in connection with the performance of tristructural isotropic (TRISO) coated particle fuel for high temperature gas-cooled nuclear reactors. Ion implantation diffusion couples have been revisited to continue developing a more complete understanding of Ag fission product diffusion in SiC. Ion implantation diffusion couples fabricated from single crystal 4H-SiC and polycrystalline 3C-SiC substrates and exposed to 1500–1625°C, were investigated by transmission electron microscopy and secondary ion mass spectrometry (SIMS). The high dynamic range of SIMS allowed for multiple diffusion régimes to be investigated, including enhanced diffusion by implantation-induced defects and grain boundary (GB) diffusion in undamaged SiC. Estimated diffusion coefficients suggest GB diffusion in bulk SiC does not properly describe the release observed from TRISO fuel.

Irradiation-induced microstructural evolution and swelling of 3C-SiC

In this study, an ion-irradiated single crystal 3C-SiC under fluences of up to 20dpa at 400–1350°C was examined using synchrotron based X-ray diffraction and high resolution transmission electron microscopy. Interstitial clusters, dislocation loops, Frank loops, stacking fault loops, and voids in 3C-SiC were investigated. The high resolution TEM results show that clusters collapsed to {111} small loops when their size reached few nm with increasing temperature, and gradually develop into Frank loops with an added atomic layer along {111} at 1000°C.Interplanar spacing information of single crystal SiC was obtained from synchrotron XRD radial scan measurements. Irradiation-induced volume swelling at 400–1350°C was measured, and the anisotropic (a=b<c) swelling behavior of SiC was confirmed. In addition, humps on the right side of SiC (002) were observed, which suggested that C+/Si+-Si〈100〉 and/or C+/Si+-C〈100〉 dumbbells gave rise to diffuse scattering.

Pseudo-Hall effect in single crystal 3C-SiC(111) four-terminal devices

This article reports the first results on the strain-induced pseudo-Hall effect in single crystal 3C-SiC(111) four-terminal devices.

Development of high temperature resistant of 500 °C employing silicon carbide (3C-SiC) based MEMS pressure sensor

This works reports a packaged MEMS capacitive pressure sensor (CPS) employing single crystal 3C-SiC thin film as a diaphragm. The details of the design and fabrication steps involved bulk micromachining process. The 3C-SiC-on-Si wafer is back-etched the bulk Si to leave 3C-SC thin film by applied ProTEK PSB coating as a newly photosensitive layer. The ProTEK PSB is exposed into desired pattern of MEMS capacitive pressure sensor and the exposed pattern is developed by developer (ethylene lactate). The photosensitive can be stripped off with strong combination acid such as 2-(1-methoxy)propyl acetate, ethyl acetoacetate and photoacid generator which is attack the exposed ProTEK PSB while unexposed ProTEK PSB areas remain contact the alignment on the wafer surfaces. The prototypes of a MEMS capacitive pressure is packaged for high temperature up to 500 °C and characterized under static pressure of 5.0 MPa in a stainless steel chamber with direct capacitance measurement using LCR meter. The diaphragm of 3C-SiC thin film has the thicknesses of 1.0 µm and the size of 2.0 × 2.0 mm. At room temperature (27 °C), the sensitivity of the sensor is 0.00962 pF/MPa in the range of (1.0---5.0 MPa), with nonlinearity of 0.49 %. At 300 °C, the sensitivity is 0.0127 pF/MPa, and nonlinearity of 0.46 %. The sensitivity increased by 0.0031 pF/MPa, corresponding temperature coefficient of sensitivity is 0.058 %/ °C. At 500 °C, the maximum temperature coefficient of output change is 0.073 %/ °C being red at 5.0 MPa. The main impact of this work is the ability of the sensor to operate up to 500 °C, compare to the previous work using similar 3C-SiC diaphragm that can operates only 400 °C. The main impact of this work is the ability our CPS to operate up to 500 °C and pressure of 5 MPa to surpass the performance of previous work at lower temperature and pressure. In addition, this CPS has reliable stainless steel (SS) o-ring packaging with a direct assembly approach to reduce manufacturing cost and easy installation and maintenance environment.

Irradiation-induced microstructural change in helium-implanted single crystal and nano-engineered SiC

Microstructural evolution induced by helium implantation and subsequent heavy ion irradiation has been investigated in single crystal and nano-engineered (NE) 3C SiC. Implantation with 65keV He+ ions was performed at 277°C, and the helium depth distribution was determined by elastic recoil detection analysis (ERDA). Transmission electron microscopy (TEM) could not resolve the presence of bubbles in any of the helium-implanted single crystal SiC. However, helium platelets and small dislocation loops (∼50nm in diameter) were observed in the single crystal sample with the highest implantation fluence after 1h annealing at 700°C. Following irradiation with 9MeV Au3+ ions at 700°C, no bubbles were observed in the helium-implanted single crystal SiC, regardless of helium fluence. For the helium-implanted NE SiC, subsequent irradiation with 9MeV Au ions to a dose of 10dpa at 700°C resulted in the formation and growth of bubbles, and a bimodal helium bubble size distribution was observed at the highest helium concentration (8000appm) in the NE SiC.

Atomic configuration of irradiation-induced planar defects in 3C-SiC

The atomic configuration of irradiation-induced planar defects in single crystal 3C-SiC at high irradiation temperatures was shown in this research. A spherical aberration corrected scanning transmission electron microscope provided images of individual silicon and carbon atoms by the annular bright-field (ABF) method. Two types of irradiation-induced planar defects were observed in the ABF images including the extrinsic stacking fault loop with two offset Si-C bilayers and the intrinsic stacking fault loop with one offset Si-C bilayer. The results are in good agreement with images simulated under identical conditions.

Fracture property and quantitative strain evaluation of hetero-epitaxial single crystal 3C-SiC membrane

The following paper explores the development of a combined bulge test/micro-Raman analysis. This analysis, together with a refined load-deflection model (valid in both small and large deformation regimes, defined as the regimes in which the ratio between membrane deflection and width is smaller or larger than 1:10), allowed the determination of the elastic and optical properties of high quality single-crystal 3C-SiC squared membranes. Specifically we have evaluated the breaking strain of the membranes by measuring the breaking pressure for various membrane widths. The relation between the shift of the Raman Transverse Optical (TO) mode and the total residual strain (Δa/a) has been determined by measuring the TO shift for different membrane deflections. This relation, which allows determination of the residual strain by simply measuring the TO shift, was known only for thick samples (Olego et al) and high-oriented (100) thin films (Rohmfeld et al). Finally, we have calculated the TO stress-free value of high-quality thin single-crystal 3C-SiC/Si(100) films as 796.71 ± 0.04 cm−1.

Evaluation of Mechanical and Optical Properties of Hetero-Epitaxial Single Crystal 3C-SiC Squared-Membrane

The aim of this work is to develop the bulge test technique combined with the micro-Raman analysis and a refined load-deflection model for high quality 3C-SiC squared-membranes. By the minimization of the total elastic energy, starting from the isotropic relation between the stress tensor and the strain tensor, it is possible to calculate the relationship between the maximum deflection and the applied pressure, in both regime of small and large deflection. Furthermore, the relationship between the measured shift of Raman Transverse Optical (TO) phonon modes and the total residual strain (Δa/a) within the epitaxial 3C-SiC layer was found and in order to understand the stress distribution within the membrane, TO Raman shift maps were performed along the corner and the border of the membrane.

Anisotropy of single-crystal 3C–SiC during nanometric cutting

3C–SiC (the only polytype of SiC that resides in a diamond cubic lattice structure) is a relatively new material that exhibits most of the desirable engineering properties required for advanced electronic applications. The anisotropy exhibited by 3C–SiC during its nanometric cutting is significant, and the potential for its exploitation has yet to be fully investigated. This paper aims to understand the influence of crystal anisotropy of 3C–SiC on its cutting behaviour. A molecular dynamics simulation model was developed to simulate the nanometric cutting of single-crystal 3C–SiC in nine (9) distinct combinations of crystal orientations and cutting directions, i.e. (1 1 1) 〈−1 1 0〉, (1 1 1) 〈−2 1 1〉, (1 1 0) 〈−1 1 0〉, (1 1 0) 〈0 0 1〉, (1 1 0) 〈1 1 −2〉, (0 0 1) 〈−1 1 0〉, (0 0 1) 〈1 0 0〉, (1 1 −2) 〈1 −1 0〉 and (1 −2 0) 〈2 1 0〉.In order to ensure the reliability of the simulation results, two separate simulation trials were carried out with different machining parameters. In the first trial, a cutting tool rake angle of −25°, d/r (uncut chip thickness/cutting edge radius) ratio of 0.57 and cutting velocity of 10 m s−1 were used whereas a second trial was done using a cutting tool rake angle of −30°, d/r ratio of 1 and cutting velocity of 4 m s−1. Both the trials showed similar anisotropic variation. The simulated orthogonal components of thrust force in 3C–SiC showed a variation of up to 45%, while the resultant cutting forces showed a variation of 37%. This suggests that 3C–SiC is highly anisotropic in its ease of deformation. These results corroborate with the experimentally observed anisotropic variation of 43.6% in Young's modulus of 3C–SiC. The recently developed dislocation extraction algorithm (DXA) [, ] was employed to detect the nucleation of dislocations in the MD simulations of varying cutting orientations and cutting directions. Based on the overall analysis, it was found that 3C–SiC offers ease of deformation on either (1 1 1) 〈−1 1 0〉, (1 1 0) 〈0 0 1〉, or (1 0 0) 〈1 0 0〉 setups.

Microstructural investigation of Si-ion-irradiated single crystal 3C-SiC and SA-Tyrannohex SiC fiber-bonded composite at high temperatures

Silicon carbides (SiCs) are considered as one of the promising candidates for structural and core materials used in fusion reactor and high temperature gas-cooled reactor (HTGR) due to its high thermal stability, and good resistance to irradiation and chemical attack. Single crystal 3C-SiC with less intrinsic defects was used to precisely characterize the radiation-induced defects in 3C-SiC. In addition, there are limited discussions related to radiation effect of SA-Tyrannohex fiber-bonded composite at high temperatures. Therefore, in this study, single crystal 3C-SiC thin film and SA-Tyrannohex SiC fiber-bonded composite were irradiated at 1000–1350°C with 7MeV Si3+ ion to simulate the neutron irradiation in reactors. The microstructure of the irradiated SiC was examined by using high resolution transmission electron microscope (HRTEM). In irradiated single crystal 3C-SiC, high resolution images showed that the planar defects were extrinsic stacking faulted loop with changing atomic sequences and intrinsic stacking faulted loop, i.e. vacancy loop. In addition, dislocation loops, voids, and edge dislocations in SA-Tyrannohex SiC fiber-bonded composite after irradiation were investigated. Besides, larger voids (with diameter 10–40nm) formed in alumina with preferred orientation after irradiation perhaps resulting in degradation of strength of the SA-Tyrannohex SiC fiber-bonded composite.

A quantitative assessment of nanometric machinability of major polytypes of single crystal silicon carbide

The influence of polymorphism on nanometric machinability of single crystal silicon carbide (SiC) has been investigated through molecular dynamics (MD) simulation. The simulation results are compared with silicon as a reference material. Cutting hardness was adopted as a quantifier of the machinability of the polytypes of single crystal SiC. 3C-SiC offered highest cutting resistance (∼2.9 times that of silicon) followed by the 4H-SiC (∼2.8 times that of silicon) whereas 6H-SiC (∼2.1 times that of silicon) showed the least. Despite its high cutting resistance, 4H-SiC showed the minimum sub-surface crystal lattice deformed layer depth, in contrast to 6H-SiC. Further analysis of temperatures in the cutting zone and the percentage tool wear indicated that single point diamond turning (SPDT) of single crystal SiC could be limited to either 6H-SiC or 4H-SiC depending upon quality and cost considerations as these were found to be more responsive and amenable to SPDT compared to single crystal 3C-SiC.