Single Crystal 3C-SiC Research Articles

Exploring defect behavior in helium-irradiated single-crystal and nanocrystalline 3C-SiC at 800°C: A synergy of experimental and simulation techniques

In this study, single crystal (sc) and nanocrystalline (nc) 3C-SiC samples were subjected to 30 keV He ion irradiation across various doses while maintaining a temperature of 800 °C. Employing techniques including Raman spectroscopy, transmission electron microscopy (TEM), and nanoindentation, the alterations in microstructure and hardness resulting from He irradiation with various fluences were examined.In sc-SiC, irradiation prompted the formation of He platelets, resulting in a hardness increase of 7 GPa. In contrast, nc-SiC, characterized by a higher stacking fault density, exhibited the formation of bubbles, primarily at grain boundaries (GBs), with fewer occurrences within the grain interior, leading to a hardness increase of 1 GPa. Notably, in both sc- and nc-SiC, hardness reached saturation and subsequently stabilized or declined with increasing He fluence.Through molecular dynamics (MD) cascade simulations, we discerned that various planar defects do not uniformly contribute to enhancing radiation resistance. For example, intrinsic stacking faults (ISF) and twins in SiC played a substantial role in altering defect density and configurations, thereby facilitating point defect annihilation. Conversely, extrinsic stacking faults (ESF) and Σ3 GBs had a limited impact on defect production during a cascade.Furthermore, calculations of cluster diffusivity revealed an accelerated movement of He-vacancy towards GBs compared to bulk material and other planar defects. Moreover, the scarcity of point defects and constrained mobility of He atoms towards stacking faults in nc-SiC elucidated the marked tendency of He to form platelets in sc-SiC.Additionally, our findings established a correlation between the calculated indentation hardness and the geometry of He defects, consistent with experimental results from nanoindentation. These results significantly contribute to ongoing efforts to design SiC materials with heightened radiation tolerance.

Analysis of single-crystal 3C-SiC subsurface damage mechanisms based on molecular dynamics indentation speed

Analysis of single-crystal 3C-SiC subsurface damage mechanisms based on molecular dynamics indentation speed

The influence of drilling speed on the evolution mechanism of subsurface defects in single crystal 3C-SiC in molecular dynamics

The influence of drilling speed on the evolution mechanism of subsurface defects in single crystal 3C-SiC in molecular dynamics

SiC-based high electron mobility transistor

This paper describes the fabrication of a SiC-based high electron mobility transistor (HEMT). A single-crystal 3C–SiC layer was grown on a C-face 4H–SiC substrate, and 2D electron gas was induced at the 3C–SiC/4H–SiC heterointerface due to the unique polarization physics. The measured Hall mobility of the 2DEG was 586 cm2/V s at room temperature. Source, gate, and drain electrodes were fabricated on the 3C–SiC surface. The drain current for the fabricated SiC-HEMT was measured to be 47.5 mA/mm, and the transconductance was estimated to be 13.5 mS/mm.

Molecular dynamics simulation-based study of single-crystal 3C-SiC nano-indentation with water film

Molecular dynamics simulation-based study of single-crystal 3C-SiC nano-indentation with water film

SЕNSORS BASED ON POLYCRYSTALLINE 3C-SiC: IMPACT OF BORON DOPING

As a chemically inert wide bandgap semiconductor material with high hardness and thermal conductivity, stable electrical characteristics, silicon carbide SiC is attractive for harsh environment electronics and sensors applications. The concept of harsh environment includes extremes of temperature, pressure, shock loads, radiation and chemical attacks those arise in aircraft and automotive engines, industrial gas turbines, during oil and gas exploration, etc.
 Lower growing temperatures of polycrystalline cubic silicon carbide, pc-3C-SiC, compared to monocrystalline allow to significantly reduce its cost and expand the possibilities of application. It follows from previous works that the thermal sensitivity of pc -3C-SiC can be significantly increased by doping with an acceptor impurity of boron during the growth of the material. The purpose of this work is to determine the properties of pc-3C-SiC doped with boron for the creation of photosensors and thermosensors, as well as thermal anemometers for extreme operating conditions.
 It is shown that pс-3C-SiC doping with a boron impurity in the growth process causes the formation of acceptor-type centers in the band gap and the appearance of features in the photosensitivity spectrum, which may be of practical interest for photovoltaics. For temperatures T > 150K, the conductivity of the doped sample increases almost exponentially with an activation energy of 0.28 eV, which is close to the activation energy of the photoconductivity of the same sample. This indicates that the ionization process of equilibrium and non-equilibrium charge carriers occurs from the same impurity centers. Boron doping causes the appearance of a broad photoconductivity band with a maximum at 1.7 eV in the impurity absorption region of pc-3C-SiC, similar to the situation in single crystal 3C-SiC.
 It was determined that the temperature coefficient of resistance for boron-doped pc-3C-SiC is 3.0´10-2 K-1 at T=300K and 1.1´10-2 K-1 at T=700K, which is almost an order of magnitude higher than for thermocouples, as well as for metals from which anemometer threads are made. The discussion of the obtained results allows to associate the value of the activation energy E=0.28 eV with the level of shallow boron in pc-3C-SiC and to assume this center is a point defect containing a boron atom that replaces a silicon atom in the 3C-SiC lattice, i.e. BSi.
 Photosensors that can be used as solar cells in the near-IR range of 0.6 - 1.8 μm, and as photocells in the visible range of 0.4 - 0.6 μm are proposed. The ability of pc-3C-SiC to work in extreme operating conditions, as well as the low cost of device manufacturing technology based on it, compared to other SiC polytypes, allow it to be considered a suitable material for creating temperature sensors, thermo-anemometers and photosensors, as well as detectors for monitoring nuclear facilities.

Influence of crystallographic effect on tool wear, cutting stress, cutting temperature, cutting force and subsurface damage in nano cutting of single crystal silicon carbide

Single crystal 3C-SiC as a typical hard and brittle material. Due to its extremely high hardness and brittleness, diamond tools can have drastic wear problems in a short period of time when performing nano-machining processes. Single-crystal 3C-SiC has good anisotropy. In order to gain insight into the effect of crystal orientation on the tool wear behavior during nano-cutting, this paper investigated the tool wear for six cutting crystals downward using molecular dynamics simulation. The tool wear process was analyzed in terms of tool wear, cutting stress, cutting temperature, cutting force and subsurface damage. The results showed that the tool is subjected to large hydrostatic stress concentrations, radial forces and tool temperature concentrations during machining. Under these effects, abrasive wear, graphitic wear and amorphous phase change were produced. In addition, the clearance face of the tool is more severely worn than the rake face. By reasonably selecting the cutting crystal orientation, well control and improvement of tool wear and machined surface quality can be achieved.

Predict the fatigue unloading elastic-plastic reduction mechanism of single crystal 3C-SiC Newton layer by reconstructed multi-dimensional dynamic static combination indenter

To explore the elasto-plastic reduction mechanism of single crystal 3C-SiC Newton layer under fatigue unloading. Reconstructed multi-dimensional single crystal 3C-SiC Newton layer unloading dynamic - static combined head. The evolution law of dislocation loop, the trend of load displacement and the direction of strain concentration expansion during fatigue unloading are analyzed. According to the stress characteristics of nanoindentation process and the requirements of real indentation environment, the NVE ensemble matrix and boundary condition parameters are integrated and optimized. The influence of indenter shape on the evolution process of dislocation ring emergence, fracture and connection and the evolution mechanism are analyzed. Through diamond identification method and stress-strain analysis method, the multi-dimensional force analysis of plastic unloading of nano-indentation is realized. It is found that the yield limit of semi-circular indenter first reaches the yield limit from the elastoplastic loading stage to the plastic loading stage than the normal four-cone. Combined with the load displacement curve, the real stress characteristics of the nano-indentation single crystal 3C-SiC Newton layer are analyzed. The results show that elastoplastic reduction existed in fatigue unloading, and the generation and development of micro-dislocation rings in elastoplastic deformation reduction under fatigue unloading of different dimensions indenter are different. The ultimate yield stress of semi-circular indenter is 3.82GPa and the ultimate strain is 1 %，the ultimate yield stress of positive quad conical indenter is 6.60GPa and the ultimate strain is 1.5 %. The elasto-plastic reduction mechanism of fatigue unloading is directly driven by the plastic evolution mechanism of dislocation ring.

Vapor Deposition Growth of SiC Crystal on 4H-SiC Substrate by Molecular Dynamics Simulation

Due to the lack of appropriate experimental methods for imaging the evolution of the microstructure of materials at the growth conditions, our understanding of the physical behavior of crystal growth and defect formation during the vapor deposition growth of SiC crystals is still rather limited. In the present work, the vapor deposition growth of SiC crystal on a 4H-SiC substrate has been investigated by the molecular dynamics (MD) computer simulation method. Three different lattice planes of 4H-SiC ((0001), (112-0) and (1-100)) were selected as the surface of the substrate, and three different temperatures for substrate (2200 K, 2300 K and 2400 K) were used in growth simulations. The characteristics of the formation of different polytypes of SiC and dislocations in the grown crystals were examined. The results show that the SiC crystals were grown by a subsurface nucleation and growth mode in the vapor deposition process. For substrates with (0001) plane as the surface, the 3C-SiC single crystal was obtained in the deposited thin film. For substrates with (112-0) or (1-100) plane as the surface, the 4H-SiC single crystal was obtained instead. The temperature of the substrate was found to have a significant effect on the dislocation density generated in the grown crystals. The mechanism for the formation of Frank partial dislocations during the growth of SiC crystals has been analyzed, for which the importance of the diffusivity of atoms on the surface layer in growth has been highlighted, and it gives a good explanation of the temperature effect on dislocation formation in the grown crystals. These results can be helpful for experimental vapor deposition growth of SiC single crystals and epitaxial layers of high quality.

Molecular Dynamics Simulation Analysis of Damage and Expansion Process of Nanoindentation Single-Crystal 3C-SiC Carbide Specimens at Different Temperature

The molecular dynamics method was used to analyze the influence of simulated temperature on the damage expansion process of the 3C-SiC sample under nano-indentation loading in order to study the influence of temperature on the internal damage and expansion mechanism of the 3C-SiC single crystal sample further during the nano-indentation loading process. A simulation test platform for diamond indenter indentation was established. The process of stress and strain distribution, dislocation evolution, dislocation expansion and potential energy change were analyzed, combined with the radial distribution function and load displacement curve. The influence of temperature on the 3C-SiC material was discussed. The variation trend of the potential energy-step curve is basically the same at the temperatures of 0 K, 300 K, 600 K and 900 K. The difference in strain distribution was characterized by the influence of temperature on stress intensity, expansion direction and type. The microcosmic manifestation is the significant difference in the dislocation slip at low temperature. In the process of dislocation evolution and expansion, dislocation climbs at room temperature and increases at high temperature, which is closely related to energy release. This study has certain guiding significance for investigating the internal damage difference and temperature effect of the 3C-SiC sample.

Molecular dynamics simulation of ion-implanted single-crystal 3C-SiC nano-indentation

To improve the machinability of the brittle material 3C-SiC, a new method of ion implantation surface modification is proposed. Molecular dynamics simulations were employed to investigate the mechanical properties and defect evolution of ion-implanted single-crystal 3C-SiC under nano-indentation. The effects of implantation dose, implantation energy, and implantation angle on the force, dislocation, hardness, and elastic modulus were discussed. The results revealed that ion implantation can reduce the hardness and elastic modulus, and improve the plasticity. Besides, the nucleation of dislocation is suppressed by ion implantation. It showed that the higher the implantation dose, the lower the force, the lower the hardness and elastic modulus, whereas those of implantation energy were the opposite. Therefore, the optimum implantation dose and energy can be obtained by comparing the above characteristics. Moreover, the channel effect was revealed under different implantation angles. Finally, through theoretical model analysis, it demonstrated that ion implantation affects the direction and size of normal stress. Thus, this method is favorable to material advanced manufacturing processes for enhancing the plasticity of the brittle single-crystal SiC.

Effects of recoil spectra and electronic energy dissipation on defect survival in 3C-SiC

The coincidence of electronic and damage energy dissipation from energetic ions to an atomic lattice can significantly affect damage production along the ion trajectory due to spatial overlap of inelastic and elastic processes. Damage production and disordering in single crystal 3C-SiC from 5 MeV Si and 10 MeV Au ions is investigated using ion-channeling experiments. While defects are created by damage energy dissipation via elastic scattering, electronic energy dissipation via electron-phonon coupling decreases defect survival along the ion trajectory for Si ions. The more energetic recoil spectrum for 10 MeV Au ions leads to weaker spatial coupling of electronic and damage energy dissipation processes, and damage production is only weakly affected.

Depth-sensing ductile and brittle deformation in 3C-SiC under Berkovich nanoindentation

The interplay between ductile and brittle deformation modes in hard brittle materials exhibits a strong size effect. In the present work, indentation depth-dependent deformation mechanisms of single-crystal 3C-SiC under Berkovich nanoindentation are elucidated by finite element simulations and corresponding experiments. A novel finite element framework, that combines a crystal plasticity constitutive model for describing dislocation slip-based ductile deformation and a cohesive zone model for capturing crack initiation and propagation-induced brittle fracture, is established. The utilized parameters in the crystal plasticity model of 3C-SiC are calibrated according to the load-displacement curves obtained from corresponding Berkovich nanoindentation experiments. Subsequent finite element simulations and experiments of nanoindentation jointly reveal co-existing microscopic plastic deformation and brittle fracture of 3C-SiC at different indentation depths, which significantly affect the observed macroscopic mechanical response and surface pile-up topography. In particular, the predicted morphology of surface cracks at an indentation depth of 500 nm agrees well with experimental observation, and the correlation of crack initiation and propagation with surface pile-up topography is theoretically analyzed.

Microscopic origin of black spot defect swelling in single crystal 3C-SiC

In this study, we perform a series of simulation of a high-energy particle irradiation on a 3C-SiC at low temperature through molecular dynamic analysis. In order to determine the formation mechanism of black spot defects (BSD), the evolution of defect clusters during the cascade process is examined. Simulation results show that there are more isolated interstitials scattering across the structure while the less mobile vacancies are concentrated in defect clusters, which is consistent with the depleted zone theory proposed by Brinkman [3]. These results also match the TEM observation and simulation results done by Lin et al. [4] and support the argument that black spot defects are in fact vacancy-rich regions, with individual interstitials spreading into bulk, stretching the lattice structure.

Irradiation-induced point defects enhance the electrochemical activity of 3C-SiC: An origin of SiC corrosion

As silicon carbide (SiC) is an inert material, it has attracted attention as an alternative material for the core components of nuclear fuel cladding. However, the corrosion of SiC under neutron irradiation has been reported, and this has been a bottleneck issue. Here, we semi-quantitatively introduced point defects into single crystal 3C-SiC layers by ion irradiation, and investigated their corrosion behavior in terms of the electrochemical activity associated with the point defects. The results showed a shift in corrosion potential and an increase in the corrosion current due to the introduction of defects. However, in the case of aluminum (Al)-doped SiC, these changes were more moderate than in the cases of the nitrogen (N)- or boron (B)-doped material, implying that Al-doped SiC has a better tolerance against corrosion.

A large pseudo-Hall effect in n-type 3C-SiC(1 0 0) and its dependence on crystallographic orientation for stress sensing applications

The pseudo-Hall effect in n-type single crystal 3C-SiC(100) with low carrier concentration has been investigated. Low pressure chemical vapor deposition was used to grow the single crystal n-type 3C-SiC(100) and Hall devices were fabricated by photolithography and dry etch processes. A large pseudo-Hall effect was observed in the grown thin films which showed a strong dependence on the crystallographic orientation. N-type 3C-SiC(100) with low carrier concentration shows a completely different behavior of pseudo-Hall measurements as compared to the p-type 3C-SiC(100). Contrary to p-type, the effect is maximum along [100] crystallographic orientation and minimum along [110] orientation. Moreover, the observed pseudo-Hall effect is 50% larger than p-type with higher carrier concentration grown by the same process which makes n-type 3C-SiC(100) with low carrier concentration more suitable material for designing highly sensitive micro-mechanical sensors.

Molecular dynamics simulation in single crystal 3C-SiC under nanoindentation: Formation of prismatic loops

We investigate the formation mechanism of prismatic loops in a 3C-SiC single crystal subjected to nanoindentations on its (111) and (110) surface with a fictitious spherical indenter using molecular dynamics simulation. On the (111) surface, the simulated plastic deformation proceeds with the nucleation and expansion of shear loops, which react with each other to form prismatic loops eventually. Further analysis reveal that the prismatic loops form from one single shear loop or two independent shear loops. For the former, the two screw components of one shear loop undergo cross-slip and form a prismatic loop by the "lasso"-like mechanism. For the latter, two independent shear loops intersect and evolve into a prismatic loop by an extended "lasso"-like mechanism, which is also manifested in the nanoindentation on 3C-SiC (110). These results could provide a further understanding for plastic deformation in 3C-SiC nanocrystal materials.

Structural properties and parameters of epitaxial silicon carbide films, grown by atomic substitution on the high-resistance (111) oriented silicon

The structure, composition and physical parameters of multilayer silicon carbide system synthesized by atom substitution method on the surface of low-dislocation single-crystal (111) oriented silicon were studied by Raman spectroscopy, ellipsometry, X-ray reflectometry, electron diffraction, IR spectroscopy, X-ray diffraction, AFM and profilometry. It was revealed that SiC films consist of layers, differing in SiyC composition, structure and thickness. The upper layers is a single-crystal 3C-SiC and the lower layers lying in depth of the substrate contain silicon carbide nanocrystals with a high degree of structure perfection and average size of 3–7 nm capable of preferential orientation (311), as well as large crystals (60–260 μm). The presence of cubic (3C-SiC) and hexagonal (mainly, 2H-SiC) polytypes with largest content of crystalline SiC phases in films with the composition closest to stoichiometric was established. In all samples there is carbon in super stoichiometric state, and its structure depends on the synthesis conditions.

Interaction between helium and intrinsic point defects in 3C-SiC single crystal

Silicon carbide (SiC) is a candidate structural material for fission and fusion reactors as well as an important wide band-gap semiconductor for electronic devices. Using first-principles calculations, we systemically investigate the energetics and stability of helium (He) atoms and intrinsic point defects inside single-crystalline 3C-SiC. We find that the formation energy of interstitial He is lower than those of point defects. Inside 3C-SiC, the He-C interaction is stronger than He-Si. Hence, the interstitial He atom in the Si tetrahedral site has a stronger interaction with the six C atoms in the second nearest neighbor than the four nearest neighboring Si atoms. For interstitial He atoms, the equilibrium He-He distance is about 1.81 Å with a weak attraction of 0.09 eV. According to the binding energies of Hen (n = 2–4) clusters, He interstitials can form He bubbles without involving other types of structural defects. Moreover, a Si (C) monovacancy can accommodate up to 11 (9) He atoms. The Hen clusters trapped in the Si or C monovacancy induce large internal pressure in the order of magnitude of GPa and thus facilitate the creation of a new vacancy at the nearby lattice site.

Piezo-Hall effect and fundamental piezo-Hall coefficients of single crystal n-type 3C-SiC(100) with low carrier concentration

This article reports the results on the piezo-Hall effect in single crystal n-type 3C-SiC(100) having a low carrier concentration. The effect of the crystallographic orientation on the piezo-Hall effect has been investigated by applying stress to the Hall devices fabricated in different crystallographic directions. Single crystal n-type 3C-SiC(100) and 3C-SiC(111) were grown by low pressure chemical vapor deposition at 1250 °C. Fundamental piezo-Hall coefficients were obtained using the piezo-Hall effect measurements as P11 = (–29 ± 1.3) × 10−11 Pa−1, P12 = (11.06 ± 0.5)× 10−11 Pa−1, and P44 = (–3.4 ± 0.7) × 10−11 Pa−1. It has been observed that the piezo-Hall coefficients of n-type 3C-SiC(100) show a completely different behavior as compared to that of p-type 3C-SiC.