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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.

Deformation-induced characteristics of surface layer strongly rely on loading condition-related operating deformation modes. In the current study we reveal the mechanisms governing machined surface formation of hard brittle monocrystalline 3C–SiC in ultrasonic elliptical vibration-assisted diamond cutting by molecular dynamics simulations. Simulation results show different deformation modes including phase transformation, dislocation activity, and crack nucleation and propagation, as well as their correlations with surface integrity in terms of machined surface morphology and subsurface damage. In particular, molecular dynamics simulations of ordinary cutting are also carried out, which demonstrate the effectiveness of applying ultrasonic vibration of cutting tool in decreasing machining force and suppressing crack events, i.e., promoting ductile-mode cutting for achieving high surface integrity. The physical mechanism governing the machining differences between the two machining processes are also revealed. Furthermore, the effect of cutting depth on machined surface integrity under vibration-assisted cutting and ordinary cutting is addressed. [ABSTRACT FROM AUTHOR]

This work presents theoretical studying the neutral divacancy, i.e., the Ky5 center that is one of the dominant defects in 3C-SiC bulk crystals subjected to relatively high dose of neutron irradiation. Being the paramagnetic center, the extended defect Ky5 shows the value of the zero field splitting (ZFS) in the electron paramagnetic resonance (EPR) signal D = 443⋅10 –4 cm –1 and 454⋅10 –4 cm –1 in two modifications. To understand the ZFS value, relativistic ab initio calculation has been carried out for obtaining the electron structure of 3C-SiC crystal containing the defect Ky5. Using the WIEN program package, the self-consisting values of the electron density ρ and controlling ρ potential V have been found. Based on the obtained values ρ and V, the contributions in ZFS from dipole-dipole and spin-orbit interactions have been found. It has been shown that the main contribution stems from the dipole-dipole interaction. Spin-orbit interaction gives a negligible contribution to ZFS. Due to the relativistic approach, spin-up and spin-down values of the electron density have been obtained, which permits to calculate the hyperfine fields at the nuclei in environment of the divacancy in 3C-SiC.

Cubic silicon carbide (3C–SiC) is an excellent protective film on graphite and has been fabricated via laser chemical vapor deposition (LCVD) with an extremely high deposition rate by our research group. To understand comprehensively its growth behavior, the polycrystalline 3C–SiC thick films with the preferred orientation of <111> and <110> were characterized by diverse measurements, especially electron back-scatter diffraction (EBSD). Along the growth direction of the <110>-oriented 3C–SiC, the microstructure changed from equiaxed grains to elongated grains with <111> orientation, and eventually the <110>-oriented columnar grains. The stacking faults in the <110>-oriented 3C–SiC could be marked as <11–20>-oriented 6H–SiC. On the other hand, in the <111>-oriented 3C–SiC films, the microstructure changed from mainly equiaxed grains to large columnar grains. The high-density stacking faults in <111>-oriented 3C–SiC films may lead to the identification of the nominal 2H, 4H and 6H polytypes by Raman spectra and EBSD. The (0001) planes of 2H-, 4H–SiC are perpendicular to the growth direction, while that of 6H–SiC are parallel. [ABSTRACT FROM AUTHOR]

An insight into electronic structure and optical feature of S-adsorbed 3C–SiC (111) surface is carried out employing first-principles calculation. It is found that the T o and B position systems with adsorption energies of 3.880 and 3.895, respectively, are relatively stable compared to the T w and C systems. Impurity energy levels are present near Fermi level in C and T w position adsorption systems and the band-gap decreases obviously in the two systems. A raindrop-like electron cloud of S atom can be observed in T w adsorption system and the order of the chemical bond strength in the adsorption system is (B , T o ) > T w > C. The B and T o adsorption systems have good light permeability in the visible and infrared regions, while the C and T w adsorption systems are relatively suitable as dielectric materials and have high service life when they as devices in the ultraviolet region. [ABSTRACT FROM AUTHOR]

Semiconductor memories are becoming more and more present in the most hostile environments. In this paper, the electrical behavior of the 6T-SRAM memory cell in 3C-SiC in 130 nm CMOS technology was studied. The study of the effect of the cell ratio (CR), supply voltage (VDD) and temperature (T) on the static noise margin (SNM), as well as the influence of temperature on write time showed that this cell is characterized by a low power (P = 27 nW), a high speed (write time τwrite = 0.305 ns) and a wide noise margin (RSNM = 320 mV), and also it works under a low voltage VDD = 1.2 V and a high temperature up to 350 °C. The comparison with the literature has shown that the 6T-SRAM cell in SiC with 130 nm CMOS technology is characterized by good electrical behavior and high electrical performance. [ABSTRACT FROM AUTHOR]

Amorphization plays an important role in ceramic deformation under mechanical loading. In the present work, we investigate the elasto-plastic deformation mechanisms of monocrystalline cubic silicon carbide (3C–SiC) in spherical nanoindentation by means of molecular dynamics simulations. The indentation-induced amorphization and its interactions with other deformation modes are emphasized. Initially, the suitable empirical potential capable of accurately characterizing the mechanical and defect properties of monocrystalline 3C–SiC, as well as the propensity of phase transformation from 3C–SiC to amorphous SiC, is rationally selected by benchmarking of different empirical potentials with experimental data and density functional theory calculations. Subsequently, the inhomogeneous elastic-plastic transitions during nanoindentation of monocrystalline 3C–SiC, as well as their dependence on crystallographic orientation, are investigated. Phase transformations including amorphization are analyzed using combined methods based on radial distribution function and bond angle distribution. Our simulation results demonstrate that before plasticity initiation-related "pop-in" event, each indented-monocrystalline 3C–SiC experiences a pure quasi-elastic deformation governed by the formation of amorphous structures. And this process of amorphization is fully reversible for small indentation depths. Further amorphization and dislocation nucleation jointly dominate the incipient plasticity in 3C–SiC nanoindentation. It is found that the indentation-induced defect zone composed of amorphous phase and dislocations is more pronounced in 3C–SiC(010) than that in the other two orientations of (110) and (111). [ABSTRACT FROM AUTHOR]

This work demonstrates the systematic investigation of the effects of high temperature on key performance parameters including speed, sensitivity, stability, and repeatability of a 3C-SiC/Si ultraviolet (UV) photodetector (PD) at various operating temperatures ranging from 50°C to 200°C. The device with very low dark current (∼ 0.08 pA) exhibited high sensitivity of 4466 and fast rise and decay times of 0.34 s and 0.30 s at 50°C to exposure of 254 nm UV light at a bias voltage of 20 V. Additionally, the device showed very good performance at a low operating voltage of 0.5 V and high temperature of 200°C, with a rise time of 2.68 s and decay time of 1.44 s, while maintaining good stability and repeatability. The slight decrease in performance (sensitivity from 4466 to 932) at 200°C was attributed to the increase in lattice scattering at elevated temperatures, leading to a decrease in carrier mobility. Moreover, the device was fabricated using a very cost-effective process flow. Consequently, this study can contribute to the development of low-power, fast, highly sensitive, and cost-effective 3C-SiC UVPDs for use in high-temperature photonic applications. [ABSTRACT FROM AUTHOR]

The effect of the high-temperature helium irradiation on microstructural evolution of 3C-SiC was investigated by the combination of Raman spectroscopy, conventional transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). 3C-SiC wafers were irradiated with 130 keV He+ ions at fluences of 2 × 1016 He+/cm2, 4 × 1016 He+/cm2 and 2 × 1017 He+/cm2 at 1000℃. Helium bubbles, dislocation loops, and their interaction with the stacking faults were focused on and characterized by TEM. Helium bubbles preferentially nucleate and grow on stacking faults. Bubble links on the (100) plane in 3C-SiC are formed. In addition, stacking faults can effectively trap irradiation-induced lattice defects to enhance their recovery. The type of irradiation-induced lattice defects and elemental distribution are also investigated. The research results are valuable for the 3C-SiC used in the advanced nuclear energy systems. [ABSTRACT FROM AUTHOR]

Despite the recent advances in 3C-SiC technology, there is a lack of statistical analysis on the reliability of SiO2 layers on 3C-SiC, which is crucial in power MOS device developments. This article presents a comprehensive study of the medium- and long-term time-dependent dielectric breakdowns (TDDBs) of 65-nm-thick SiO2 layers thermally grown on a state-of-the-art 3C-SiC/Si wafer. Fowler–Nordheim (F-N) tunneling is observed above 7 MV/cm and an effective barrier height of 3.7 eV is obtained, which is the highest known for native SiO2 layers grown on the semiconductor substrate. The observed dependence of the oxide reliability on the gate active area suggests that the oxide quality has not reached the intrinsic level. Three failure mechanisms were identified and confirmed by both medium- and long-term results. Although two of them are likely due to extrinsic defects from material quality and fabrication steps, the one dominating the high field (>8.5 MV/cm) should be attributed to the electron impact ionization within SiO2. At room temperature, the field acceleration factor is found to be ≈ 0.906 dec/(MV/cm) for high fields, and the projected lifetime exceeds 10 years at 4.5 MV/cm. [ABSTRACT FROM AUTHOR]

Abstract—In this article, we studied the growth characteristics of AlN epitaxial layers on 3С-SiC/Si(111) templates at various values of atomic flux of aluminum at a constant growth temperature and a constant flow of atomic nitrogen. The AFM method was used to study the morphology of the resulting structures. The minimum roughness was achieved at a growth rate of 150 nm/h on on-axis templates, and at 90 nm/h on off-axis templates. Epitaxial layers of hexagonal AlN with root mean square roughness of less than 3 nm were obtained on 3С-SiC/Si(111) templates with a diameter of 100 mm, in which there was no grain structure. Single-crystal AlN (0002) layers with FWHM (ω‑geometry) values of about 1.4° were obtained. [ABSTRACT FROM AUTHOR]

AlN nucleation layer is the key issue for the performance of GaN high frequency telecommunication and power switching systems fabricated after heteroepitaxy on Silicon or Silicon Carbide. In this work, we demonstrate and explain both the low level and the origin of propagation losses in GaN/3C–SiC/Si High Electron Mobility Transistors (HEMTs) at microwaves frequencies, in view of providing efficient circuits. First, it is shown that the use of 3C–SiC as an intermediate layer between the Si substrate and the GaN epitaxial layer drastically decreases RF propagation losses. Using Secondary Ion Mass Spectroscopy (SIMS) measurements, we demonstrate that dopant in-diffusion (both Al and Ga) into the 3C–SiC pseudo-substrate remains confined beneath the interface. Furthermore, by combining scanning capacitance microscopy (SCM) and scanning spreading resistance microscopy (SSRM), the 2D profile shows the presence of a slightly conductive zone beneath the AlN/3C–SiC interface that is highly limited (less than 50 nm) whatever the growth conditions of the (Al, Ga)N layers on 3C–SiC explaining the low propagation losses obtained for such devices. This behavior differs from the one previously observed for GaN growth on Si substrate. This work demonstrates the importance and efficiency of the 3C–SiC intermediate layer when used as a pseudo-substrate increasing not only the crystalline quality of the subsequent (Al, Ga)N layers but also permits to achieve high potential GaN power devices as it is crucial. [ABSTRACT FROM AUTHOR]

Gas sensors are devices that can detect and/or discriminate gases in their surroundings. Some of these devices are based on vibrating structure covered with a coating sensitive to the species to detect. But such a layer can cause device failures issues like ageing, low reliability and high response time. Nonetheless, gas sensors are of importance for industrial environments in many applications. In addition, in some cases, the sensors must operate in harsh environments, that can lead to a severe degradation of the devices. In this paper, we propose to review different MEMS devices, without any sensitive layer, for gas detection applications. The objective is to measure a physical property of the gas in order to determine its concentration. With the microsystem devices, limits of detection as low as 0.2 % has been obtained, illustrating the capabilities of the structures elaborated. And in our case, due to the absence of sensitive film that must be adapted according to the species to detect, it leads to generic sensors, compatible with many different gases. Moreover, by combining the measures of 2 physical parameters, the discrimination of the gases, with their respective concentrations, is accessible. [ABSTRACT FROM AUTHOR]

Machining of brittle ceramics is a challenging task because the requirements on the cutting tools are extremely high and the quality of the machined surface strongly depends on the chosen process parameters. Typically, the efficiency of a machining process increases with the depth of cut or the feed rate of the tool. However, for brittle ceramics, this easily results in very rough surfaces or even in crack formation. The transition from a smooth surface obtained for small depths of cut to a rough surface for larger depths of cut is called a brittle-to-ductile transition in machining. In this work, we investigate the mechanisms of this brittle-to-ductile transition for diamond cutting of an intrinsically brittle 3C-SiC ceramic with finite element modeling. The Drucker–Prager model has been used to describe plastic deformation of the material and the material parameters have been determined by an inverse method to match the deformation behavior of the material under nanoindentation, which is a similar loading state as the one occurring during cutting. Furthermore, a damage model has been introduced to describe material separation during the machining process and also crack initiation in subsurface regions. With this model, grooving simulations of 3C-SiC with a diamond tool have been performed and the deformation and damage mechanisms have been analyzed. Our results reveal a distinct transition between ductile and brittle cutting modes as a function of the depth of cut. The critical depth of cut for this transition is found to be independent of rake angle; however, the surface roughness strongly depends on the rake angle of the tool.

3C-SiC is an emerging material for MEMS systems thanks to its outstanding mechanical properties (high Young’s modulus and low density) that allow the device to be operated for a given geometry at higher frequency. The mechanical properties of this material depend strongly on the material quality, the defect density, and the stress. For this reason, the use of SiC in Si-based microelectromechanical system (MEMS) fabrication techniques has been very limited. In this work, the complete characterization of Young’s modulus and residual stress of monocrystalline 3C-SiC layers with different doping types grown on and oriented silicon substrates is reported, using a combination of resonance frequency of double clamped beams and strain gauge. In this way, both the residual stress and the residual strain can be measured independently, and Young’s modulus can be obtained by Hooke’s law. From these measurements, it has been observed that Young’s modulus depends on the thickness of the layer, the orientation, the doping, and the stress. Very good values of Young’s modulus were obtained in this work, even for very thin layers (thinner than 1 μm), and this can give the opportunity to realize very sensitive strain sensors.

First‐principles calculations and thermodynamics analyses were combined to study the surface stabilities of 3C–SiC and H2O adsorption on the (110) surface. The stoichiometric (110) surface was predicted to be generally the most stable. Only at the extremely C‐poor condition, the nonstoichiometric Si‐terminated (100) could become more energetically favored. The adsorption and dissociation of single H2O molecule on the 3C–SiC (110) were then comparatively investigated. Calculations show that H2O molecules prefer to partially dissociate into one hydroxyl OH and one H adsorbed at the top‐most Si and C sites, respectively, leading to the formation of a hydrogen network on the surface. The calculated equilibrium adsorption diagram further suggested that the 3C–SiC (110) surface can be only either completely clean or fully covered by the partially dissociated species of H2O, for a wide range of temperature and the partial potential of H2O. [ABSTRACT FROM AUTHOR]

An ultraviolet laser (λ = 266 nm) operated in pulsed mode and a diode laser (λ = 1060 nm) operated in continuous mode were simultaneously applied to create a hybrid laser chemical vapor deposition (CVD) approach. Fine‐grained 3C‐SiC thick films were prepared via hybrid laser CVD by using SiCl4, CH4 and H2 as precursors. The effects of the ultraviolet laser on the preferred orientations, microstructures, microhardness values and deposition rates of 3C‐SiC thick films were investigated. The 3C‐SiC thick films that were prepared at 4 kPa via diode laser CVD exhibited <110>‐orientations and 5‐100 µm grain sizes, whereas those prepared via hybrid laser CVD were randomly oriented with 0.5‐5 µm grain sizes. Compared to diode laser CVD, the additional irradiation of the ultraviolet laser in the hybrid laser CVD improved the Vickers microhardness values of the 3C‐SiC thick films from 30 to 35 GPa, and the maximum deposition rate was also increased from 935 to 1230 µm/h. [ABSTRACT FROM AUTHOR]

A qualitative and quantitative study was performed on the carbonization temperature (TC) and carbonization time (tC) with respect to the microstructure and growth rate (Rg) of a 3C-SiC epitaxial layer on Si (111) substrates by carbonization via laser chemical vapor deposition (LCVD). The results showed that the density and size of the voids depended strongly on TC. The voids were sealed, and thin films were formed continuously and uniformly after a carbonization time of 6 min at TC = 1200 °C. Rg was also dependent on TC, and increased from 0.43 to 1.35μm·h−1 with increases in TC from 1000 to 1200 °C. These deposition rates are 10 to 100 times greater than those of observed for conventional CVD methods. [ABSTRACT FROM AUTHOR]

Ab initio calculations were carried out to investigate the behaviors of interstitial He n clusters in 3C-SiC. Based on the simulation and experimental results of SiC, we considered two types of tetrahedral sites for He atoms to be allocated, forming an interstitial He n cluster. The compact structures of He n clusters that were alternately surrounded by the tetrahedral sites neighboring four Si atoms (T Si) and the tetrahedral sites neighboring four C atoms (T C) were investigated, and the corresponding number of tetrahedral sites in each T Si or T C layer was determined by an empirical formula. To better illustrate the interaction between He atoms, we defined one and two types of ground states when calculating the binding energies at high and low temperatures, respectively. The average binding energies of each He atom in He n clusters of different sizes were obtained, and the maximum binding energy of a He atom in the outermost layer of a He n cluster was estimated to be 0.61 eV via the number of nearest neighboring and next nearest neighboring He atoms. It is of interest to note that the self-trapping mechanism was not observed in 3C-SiC, since He atoms remained in their respective tetrahedral sites at low temperatures due to their high migration barrier and weak binding energy. In contrast, the compact He n clusters tended to dissolve at high temperatures because the He atoms located at T C sites tended to migrate into T Si sites. Image 1 • Two types of tetrahedral sites are considered for He atoms to be allocated. • He n clusters that are alternately surrounded by T Si and T C sites are investigated. • Maximum binding energy of a He atom is estimated via the number of NN and NNN sites. • Self-trapping of He atoms is not observed in 3C-SiC at low or high temperatures. [ABSTRACT FROM AUTHOR]

In this study, a computer-aided simulation of the homo-junction thin films of solar cell was presented. Different solar cell structures PN and PIN based on 3C-SiC have been studied and the effects of the illumination intensity on the electrical properties of these solar cells such as: the short- circuit current density (Jsc), the open circuit voltage (Voc), the factor (FF) and photovoltaic conversion efficiency (η) were investigated. The numerical simulations were performed at different conditions of illumination : 90mW.cm− 2, 100mW.cm− 2and 135mW.cm− 2, under absolute temperature T = 300 K. The results have demonstrated that the maximum electrical conversion efficiency of about 23.24 % and 23.41% for PN and PIN junction, respectively, which makes the two proposal structures suitable as photovoltaic (PV) solar cell applications. [ABSTRACT FROM AUTHOR]

First-principles calculations based on density functional theory (DFT) were performed to investigate the doping Mg on the interfacial bonding of Al(111)/3C-SiC(111) interface. The calculated work of adhesion suggests that the Si-terminated and C-terminated interface yields the largest W ad value of 1.86 J/m2 and 3.46 J/m2 at Top-site, respectively. The calculated results of interface energy γ int of Si-terminated and C-terminated Al(111)/3C-SiC(111) interfaces were −0.63 J/m2 and -0.24 J/m2, respectively, implying that there was an inter-diffusion between interfacial atoms. The doping of Mg increased the W ad value of Si-terminated interface from 1.86 J/m2 to 3.07 J/m2 and decreased the W ad value of C-terminated interface from 3.46 J/m2 to 3.10 J/m2, suggesting that the doping Mg has the opposite effect on the bonding of these two interfaces. The calculation of the electronic structure showed that interfacial bonding of these two terminated interfaces was a mixture of covalent, ionic and metallic bonds. The doping of Mg enhances the covalent bonding strength of Si-Al bonding states for Si-Mg bond and anti-bonding states for C-Mg bond, respectively. It can be concluded that the doping of Mg was beneficial to the bonding of the Si-terminated interface, but exhibited a negative effect on the binding of C-terminated interface. • Effect of Mg addition on Al (111) /3C-SiC (111) interface is studied by first-principles. • The wettability and bonding strength of the Si-terminated interface are improved. • The bonding strength of C-terminated Al (111) /3C-SiC (111) interface is weakened. • The covalent bonding strength of Si-Al bonds and C-Al bonds is enhanced. [ABSTRACT FROM AUTHOR]

Abstract This paper is a report on Ohmic contacts on n-type and p-type type cubic silicon carbide (3C-SiC) layers grown on silicon substrates. In particular, the morphological, electrical and structural properties of annealed Ni and Ti/Al/Ni contacts has been studied employing several characterization techniques. Ni films annealed at 950 °C form Ohmic contacts on moderately n-type doped 3C-SiC (N D ~1 × 1017 cm−3), with a specific contact resistance of 3.7 × 10−3 Ω cm2. The main phase formed upon annealing in this contact was nickel silicide (Ni 2 Si), with randomly dispersed carbon in the reacted layer. In the case of a p-type 3C-SiC with a high doping level (N A ~5 × 1019 cm−3), Ti/Al/Ni contacts were preferable to Ni ones, as they gave much lower values of the specific contact resistance (1.8 × 10−5 Ω cm2). Here, an Al 3 Ni 2 layer was formed in the uppermost part of the contact, while TiC was detected at the interface. For this system, a temperature dependent electrical characterization allowed to establish that the thermionic field emission rules the current transport at the interface. All these results can be useful for the further development of a device technology based on the 3C-SiC polytype. [ABSTRACT FROM AUTHOR]

The elastic‐plastic deformation of 3C‐SiC thin film was investigated by a nanoindenter equipped with the Berkovich tip. Transition from pure elastic to elastic‐plastic deformation was evidenced at an approximate load of 0.35 mN, when loading the sample at several peak loads ranging from 0.5 to 5 mN. The indentation size effect observed in 3C‐SiC and was analyzed by Nix‐Gao model. In purely elastic region, the Oliver‐ Pharr hardness values were 44 ± 2 GPa. In contrast, indentation size effects were evidenced in 3C‐SiC specimen and the average value of Oliver‐Pharr hardness in the indentation size effect region was 36 ± 2 GPa. Furthermore, depth independent or intrinsic hardness extracted from Nix‐Gao was estimated as Ho = 26 ± 1 GPa which was also validated by proportional specimen resistance model, ie, H1 = 28 ± 1 and H2 = 28.5 ± 0.1 GPa. Besides, energy principle was utilized to extract Sakai Hardness as 104 GPa, which is combined elastic and elastic‐plastic response. Moreover, based on energy principle, another property, ie, work of indentation was also determined to be 20 nJ/μm3. Similarly, elastic modulus had almost depicted stabilized value of 325 ± 8 GPa in pure elastic and elastic‐plastic regions. In addition, plastic zone size was also estimated in elastic‐plastic region using Johnson cavity model at pop‐in and higher loads. Based on the first pop‐in load at 0.35 mN, the distributions of shear and principal stresses were evaluated on various slip planes to elaborate the deformation behavior. Increase in loading rate from 100 to 400 μN/s increased critical pop‐in load from 0.35 to 0.64 mN. This increase in critical pop‐in load with increasing loading rate and values of maximum contact pressure indicates that no phase assisted transformation will occur at pop‐in load. Based on theoretically calculated maximum tensile and cleavage strengths, it was affirmed that the elastic‐plastic deformation occurred due to pop‐in formation rather than tensile stresses. Moreover, it was also concluded on basis of Hertzian contact theory and Schmidt law that the highest possibility of slippage in 3C‐SiC was along the {111} glide plane. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A new multiscale method was used for examining fracture of polycrystalline 3C-SiC. • The multiscale method coupled molecular dynamics and mesoscale peridynamics. • Fracture strength followed a Hall-Petch like relation. • Fracture toughness increased with grain-size. Abstract A robust atomistic to mesoscale computational multiscale/multiphysics modeling framework that explicitly takes into account atomic-scale descriptions of grain-boundaries, is implemented to examine the interplay between grain-size and fracture of polycrystalline cubic silicon carbide (3C-SiC). A salient feature of the developed framework is the establishment of scale-parity between the chosen atomistic and the mesoscale methods namely molecular dynamics (MD) and peridynamics (PD) respectively, which enables the ability to model the effect of the underlying microstructure as well as obtain relevant new insights into the role of grain-size on the ensuing mechanical response of 3C-SiC. Material properties such as elastic modulus, and fracture toughness of single crystals and bicrystals of various orientations are obtained from MD simulations, and using appropriate statistical analysis, MD derived properties are interfaced with PD simulations, resulting in mesoscale simulations that accurately predict the role of grain-size on failure strength, fracture energy, elastic modulus, fracture toughness, and tensile toughness of polycrystalline 3C-SiC. In particular, it is seen that the fracture strength follows a Hall-Petch law with respect to grain-size variations, while mode-I fracture toughness increases with increasing grain-size, consistent with available literature on brittle fracture of polycrystalline materials. Equally importantly, the developed MD-PD multiscale/multiphysics framework represents an important step towards developing materials modeling paradigms that can provide a comprehensive and predictive description of the microstructure-property-performance interplay in solid-state materials. [ABSTRACT FROM AUTHOR]

Abstract Diamond indenters are usually regarded undeformable during nanoindentation process. However, when the sample to be indented is very hard material, the deformation of indenters should not be neglected. In order to study the effect of deformation of indenters, a study through molecular dynamics (MD) method is conducted. Deformable and rigid spherical diamond indenters are applied to indent on 3C-SiC sample. According to the simulation results, spherical indenter shows complicated deformation. The indenter is compressed during the early stage of loading process, and has a little recovery latterly. This kind of deformation largely influences the onset and development of dislocations of 3C-SiC sample during nanoindentation process. The deformation of indenter can also result in the inaccuracy measurement of actual indentation depth and hardness. In addition, load-indentation depth curves and hardness-indentation depth curves show that both of the calculated indentation force and hardness are smaller when the indenter deforms. Moreover, a correction method is put forward in this paper to eliminate the influence of deformation of spherical indenter. This research provides new insights to perfect theoretical system of nanoindentation. [ABSTRACT FROM AUTHOR]

AlGaN/GaN high electron mobility transistors (HEMTs) have established terrific features in the high-power and high-frequency applications of microwave device. In this paper, the impact of silicon carbide polymorphs substrates including 6H-SiC, 3C-SiC and 4H-SiC on the performances of AlGaN/GaN double quantum well HEMTs (DQW-HEMTs) are analyzed and investigated. The results show that the devices with 4H-SiC and 6HSiC substrates exhibit a higher transconductance of about 192 ms/mm at VDS = 15 V and a lower minimum noise figure (NFmin) of 0.48 and 0.42 dB at 10 GHz than those of devices with 3C-SiC, respectively. Whereas, DCHEMT with 3C-SiC substrate has a transconductance of about 180 ms/mm at VDS = 15 V and a minimum noise figure of 3.01 dB at 10 GHz. On the other hands, the DCHEMT with 3C-SiC substrate has lower drain gate capacitance (Cdg) and higher cut-off frequency (ft) than DC-HEMT with 4H-SiC and 6H-SiC substrates. The results demonstrate that AlGaN/GaN DH-HEMTs 4H-SiC and 6HSiC substrates are promising devices for future highpower and high-frequency electron device applications. [ABSTRACT FROM AUTHOR]

3C–SiC is an important structural material for tri-structural isotropic coated fuel particles in high-temperature gas reactors. It serves as a vital pressure vessel for gas fission products and a shielding layer for metal fission products. However, the accumulation of interstitial He atoms can lead to the formation of He bubbles, which threaten the safe service of materials. A study of how interstitial atoms affect the migration of He atoms can help us understand the nucleation of He bubbles in SiC cladding materials. The effects of H and Pd interstitials on the solution energy and migration behavior of He atoms were investigated. It was found that H favored He atoms to approach it, while Pd has the opposite effect, causing He atoms to move away from it. Under the synergistic effect of H and Pd atoms, He atoms tend to move away from the Pd interstitial, similar to the effect of the Pd interstitial alone. Furthermore, the external H interstitial strengthens the effect of Pd atoms on He atoms, drastically reducing the migration energy of He atoms away from Pd. • The effect of H and Pd atoms on the migration behavior of He atoms is studied. • H interstitials can promote the migration and aggregation of nearby He atoms. • The Pd interstitial can cause He atoms to move and aggregate away from it. • Pd atoms play a major role in the synergistic effect of H and Pd atoms on He atoms. [ABSTRACT FROM AUTHOR]

The electronic structure and the magnetic and optical properties of a 3C–SiC system co-doped with Fe and V were systematically investigated by first-principles calculations. The origin and formation mechanism of the system's magnetism were elucidated by our analyzing the density of states of each electron orbital and calculating the magnetic moments contributed by each element. The most stable doped structure was determined by our calculating the formation energy of the system at ten different doping sites. The (5, 7) doping configuration demonstrated the greatest system stability and was used to calculate the electron spin density and optical properties. Our results showed that the co-doped 3C–SiC system exhibits better optical absorption throughout the infrared and visible regions, indicating that co-doping with Fe and V is an effective approach to improve the properties of 3C–SiC materials. We found that doping introduces magnetism to the system, generates spin polarization, and increases electrical conductivity. Furthermore, the co-doped system combines the electrical properties of semiconductors and the magnetic properties of magnets, providing a promising avenue for developing new semiconductor technology and electronic devices. • (Fe, V)-co-doped 3C-SiC system combines electrical properties with magnetic properties and has higher total magnetic moments. • The magnetic properties induced by Fe and V doping arise from the interaction of p-d electron orbital hybridization. • The doping system has a significant redshift and better absorption capacity of visible light compared to the intrinsic system. [ABSTRACT FROM AUTHOR]

Chloride-based CVD growth of 3C-SiC epitaxial layers on on-axis 4H-SiC substrates has been studied using chloromethane and silane as precursors. Hydrogen chloride is utilized as additional chlorine source. Process parameters, such as growth temperature, C/Si ratio, Cl/Si ratio and temperature ramp-up condition, are investigated. Smooth 3C-SiC layers without DPB defects on the surface could be obtained with optimized process at a growth rate of 14 μm/h. Low temperature photoluminescence measurement shows sharp near bandgap emission, which verifies the good optical properties of the epitaxial layer. The growth window is wide in this process by using chlorinated precursors compared to the standard chemistry. • The 3C-SiC epilayers were CVD grown on 4H-SiC using CH 3 Cl as carbon precursor. • 3C-SiC layers with improved morphology could be grown with optimized process. • A 28 μm 3C-SiC layer with smooth surface was obtained at a growth rate of 14 μm/h. [ABSTRACT FROM AUTHOR]

Abstract This work provides a novel chemical vapor deposition technique to synthesize bamboo-like 3C-SiC nanowires (NWs) at low temperature (1200 °C) in absence of Ar gas by Si and phenolic resin powders, and catalyzed by trace nano-ZrO 2 particles. The obtained bamboo-like 3C-SiC NWs were dozens of microns in length and composed of two alternating structure units with periodical fluctuating diameter, and the diameters of nodes and stems were 50–70 nm and 40–50 nm, respectively. Nano ZrO 2 catalyst was key factor for SiC NWs formation and growth because ZrO 2 triggered reactions to generate more SiO(g) and CO(g), and activated SiO (g) and CO (g) by weakening Si–O and C–O bond strength. The reciprocal formation of ZrC and ZrO 2 occurred repeatedly led to SiC growing into bamboo-like NWs. The bamboo-like SiC NWs have good violent-blue luminescent property. [ABSTRACT FROM AUTHOR]

Abstract: Epitaxial 3C–SiC films have been deposited on Si(111) and Si(001) substrates via laser CVD with deposition rate of 12.32 and 15.56 μm/h, respectively. The activation energy of 3C–SiC on Si(111) and Si(001) was 80 and 160 kJ/mol, and the root mean square (RMS) roughness (w) as a function of the film thickness (h) follows power laws of w~h0.31 and w~h0.06, respectively. The growth mechanisms of epitaxial 3C–SiC films on Si(111) and Si(001) was investigated based on the structural analysis and roughness evolution. [ABSTRACT FROM AUTHOR]

This work presents theoretical studying the neutral divacancy, i.e., the Ky5 center that is one of the dominant defects in 3C-SiC bulk crystals subjected to relatively high dose of neutron irradiation. Being the paramagnetic center, the extended defect Ky5 shows the value of the zero field splitting (ZFS) in the electron paramagnetic resonance (EPR) signal D = 443×10-4cm-1 and 454×10-4cm-1 in two modifications. To understand the ZFS value, relativistic ab initio calculation has been carried out for obtaining the electron structure of 3C-SiC crystal containing the defect Ky5. Using the WIEN program package, the self-consisting values of the electron density r and controlling r potential V have been found. Based on the obtained values r and V, the contributions in ZFS from dipole-dipole and spin-orbit interactions have been found. It has been shown that the main contribution stems from the dipole-dipole interaction. Spin-orbit interaction gives a negligible contribution to ZFS. Due to the relativistic approach, spin-up and spin-down values of the electron density have been obtained, which permits to calculate the hyperfine fields at the nuclei in environment of the divacancy in 3C-SiC. [ABSTRACT FROM AUTHOR]

Molecular dynamics (MD) simulations are performed using the Tersoff + ZBL potential to determine the values and directional dependence of the threshold displacement energies (TDEs) for the production of point defects by carbon and silicon primary knock-on atoms (PKAs) with energies up to 400 eV in 3C-SiC and amorphous SiC (a-SiC). These materials are being considered for accident tolerant cladding materials in next generation light-water nuclear reactors and are being used in many other industrial applications. Results show that the TDEs for the displacement of a PKA or an atom in 3C-SiC, as well as those for the production of a Frenkel pair are different and highly anisotropic. The lowest energy to produce a carbon vacancy in any crystallographic direction is 14–16 eV and 38–58 eV for the C and Si PKAs, respectively. The lowest energies for the C and Si PKAs to produce a Si vacancy are 59–71 eV and 42–46 eV, respectively. The number of C vacancies produced by 400 eV C PKA and Si PKA are 4x and 1.75x the silicon vacancies produced, respectively. In a-SiC, the TDE probability distributions for the displacement of Si PKAs and of an atom differ, but are similar for C PKAs. The Si PKAs are likely to displace the less-massive C atoms at energies lower than that required to displace a Si PKA, resembling the interaction sequences in some directions in 3C-SiC. The energy to cause a C PKA displacement with 50% probability in 3C-SiC (26 eV), is more than twice that in a-SiC (13 eV). For the Si PKAs, these energies are 48 eV and 27 eV, respectively. The determined TDEs, which are consistent with the reported experimental values and those based on MD simulations, could be used in future investigations of irradiation effects. [ABSTRACT FROM AUTHOR]

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New UV–Vis–NIR light responsive Er/Tm/Yb/Y 2 O 3 -SiC composites are designed by coupling different structured Er/Tm/Yb/Y 2 O 3 upconversion luminescence materials (UCLMs) with 3C-SiC ultrafine nanocrystals (NCs) and explored as an efficient photocatalytic material. The Er/Tm/Yb/Y 2 O 3 UCLMs can convert near-infrared (NIR) light into visible light which can be absorbed by 3C-SiC NCs, thus extend the optical responsive range of the photocatalysts to NIR light region. The structure effect of UCLMs on their upconversion luminescence performance is explored, indicating that the chain-like Er/Tm/Yb/Y 2 O 3 UCLMs display much more preferable luminescence activity than flake-like structure. Compared with pure 3C-SiC NCs, both the two hybrid structures offer excellent performance in catalyzing decomposition of methylene blue (MB) under illumination of NIR light as well as UV–Vis–NIR light. Moreover, the photocatalytic activity of chain-like Er/Tm/Yb/Y 2 O 3 -SiC composites is better than that of the flake-like composites, profiting from the high light absorption efficiency induced by the multiple reflection-absorption effect. It is anticipated that this work provides new insights into the fabrication of photocatalysts with excellent light responses to a broader spectral range. [ABSTRACT FROM AUTHOR]

Noise due to the avalanche multiplication of charge carriers is the major limiting factor for determining the high frequency properties of impact avalanche transit time (IMPATT) sources. The noise level in IMPATT diodes are major concerning factor espetially at millimeter-wave (mmwave) frequency regime where the power out of the device reduces in the order of few hundred milliwatts. In the present work, the noise properties of different multiple quantum well (MQW) double-drift region (DDR) IMPATT structures based on Si~3C-SiC material system have been studied. The simulation study shows that those MQW diodes are able to produce considerably greater power with significantly less noise level at W-band (75 - 110 GHz) with contrast to their flat DDR Si counterpart. [ABSTRACT FROM AUTHOR]

This work provides a novel and green approach to synthesize 3C-SiC nanowires (NWs) by carbothermic reduction of coked rice husk and silicon powders without catalyst or extra protective atmosphere. Results show that the as-synthesized 3C-SiC NWs are well-crystallized and grow along the [1 1 1] direction, the diameters of them are in the range of 50–120 nm, and their lengths are up to dozens of micrometers. They own a face-centered cubic structure and are wrapped by a thin amorphous SiO 2 layer (∼6 nm). Meanwhile, a few stacking faults perpendicular to the growth direction exist in their crystals. These 3C-SiC NWs exhibit three ultraviolet light emission peaks at wavelengths of 435 nm, 467 nm and 572 nm, respectively, showing they possess a wide range of emission wavelengths. This study is of great significance which extends the research of 3C-SiC NWs and will bring great benefits to their practical applications in optoelectronic devices. [ABSTRACT FROM AUTHOR]

The pseudo-Hall effect in n-type single crystal 3C-SiC(1 0 0) with low carrier concentration has been investigated. Low pressure chemical vapor deposition was used to grow the single crystal n-type 3C-SiC(1 0 0) 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(1 0 0) with low carrier concentration shows a completely different behavior of pseudo-Hall measurements as compared to the p-type 3C-SiC(1 0 0). Contrary to p-type, the effect is maximum along [1 0 0] crystallographic orientation and minimum along [1 1 0] 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(1 0 0) with low carrier concentration more suitable material for designing highly sensitive micro-mechanical sensors. [ABSTRACT FROM AUTHOR]

The (001) surface of cubic silicon carbide (3C SiC) after cleaning, Ar sputtering and three different wet chemical etching procedures was thoroughly investigated via (angle resolved) XPS, HREELS, and LEED. While Ar sputtering was found to be unsuitable for surface preparation, all three employed wet chemical etching procedures (piranha/NH 4 F, piranha/HF, and RCA) provide a clean surface. HF as oxide removal agent tends to result in fluorine traces on the sample surface, despite thorough rinsing. All procedures yield a 1 × 1 Si–OH/C–H terminated surface. However, the XPS spectra reveal some differences in the resulting surface states. NH 4 F for oxide removal produces a flat band situation, whereas the other two procedures result in a slight downward (HF) or upward (RCA) band bending. Because the band bending is small, it can be concluded that the number of unsaturated surface defects is low. [ABSTRACT FROM AUTHOR]

Highly-oriented 3C-SiC possesses good out-of-plane orientation uniformity, and has more potential to obtain uniform surface quality during ultra-precision machining, compared with randomly-oriented SiC (such as RB-SiC and S-SiC, et al.). Through ultra-precision machining of highly-oriented 3C-SiC under electrolytic in-process dressing (ELID), the oxide film formed on the grinding wheel enhances the contact stiffness between the grinding wheel and the workpiece during the process. Further, compressive residual stress of 0.29 MPa on highly-oriented 3C-SiC surface conducive to the removal of material ductile was generated. It enabled ELID to perform better material ductile removal ability than conventional grinding (CG) does. On the other hand, numerous stacking faults (SFs) in highly-oriented 3C-SiC promoted the migration of dislocations in the material and generated more dislocations in the material under the shear stress of ELID grinding wheel. In addition, the accumulated dislocations at the grain boundary continued to slip to the next grain rather than resulting in dislocation pile-up and material crack due to the consistency of grain orientation. This phenomenon has the materials been ductile removal rather than brittle fracture. All above findings would provide a beneficial reference for the control of grinding process and the analysis of material removal mechanism of highly-oriented materials. • The highly-oriented 3C-SiC was machined by electrolytic process dressing (ELID) and conventional grinding (CG). • The existence of oxide film in ELID grinding can make this technology achieve better ductile removal than CG. • The micro-deformation mechanism of highly-oriented 3C-SiC under ELID grinding is analyzed based on the test results. • The highly-oriented is beneficial to reduce the accumulation of dislocations at the grain boundary. [ABSTRACT FROM AUTHOR]