The epitaxial growth of graphene on hexagonal silicon carbide polytypes on both the silicon-terminated (0001) and carbon-terminated ($000\bar 1$) faces has shown promise in the development of large area graphene production. It is important during these growth procedures to ensure that the underlying silicon carbide substrate is well ordered before the graphene growth. Regularly, this involves the use of a hydrogen etching procedure before graphene growth to remove polishing scratches and other defects from the substrate surface. Here, we present evidence that annealing silicon carbide substrates in argon gas at atmospheric pressure suppresses the onset of graphitization up to a temperature of 1500 °C and allows for regularly stepped terraces and removes surface defects. This allows substrate preparation and subsequent graphitization (by increasing the annealing temperature) to be carried out within a single process under an inert gas atmosphere.

We report the results of the systematic investigation into correlations between energetics and hexagonal stacking configurations for carbon, silicon, SiC, BN, AlN, GaN, and InN polytypes with sp3-bonded networks. The atomistic geometry, energetics, and electronic structure for these compounds with up to the periodic stacking length of L = 8 have been carefully calculated based on the density functional theory within the generalized gradient approximation (GGA). Using the Axial Next-Nearest-Neighbor Ising model extracted from the GGA calculations, we have also studied the energetics for more than 6 million kinds of nonequivalent stacking polytypes with up to L = 30, whose configurations have been deduced by the efficient polytype generation algorithm [E. Estevez-Rams and J. Martinez-Mojicar, Acta Crystallogr., Sect. A: Found. Crystallogr. 64, 529 (2008)], and illustrated some trends of structural and energetic properties for these compounds.

The p-type doping of high purity semi-insulating 4H polytype silicon carbide (HPSI 4H-SiC) by aluminum ion (Al+) implantation has been studied in the range of 1 × 1019 to 8 × 1020 /cm3 (0.39 μm implanted thickness) and a conventional thermal annealing of 1950 °C/5 min. Implanted 4H-SiC layers of p-type conductivity and sheet resistance in the range of 1.6 × 104 to 8.9 ×102 Ω□, corresponding to a resistivity in the range of 4.7 × 10−1 to 2.7 × 10−2 Ω cm have been obtained. Hall carrier density and mobility data in the temperature range of 140–720 K feature the transition from a valence band to an intraband conduction for increasing implanted Al ion concentration from 1 × 1019 /cm3 to 4 × 1020 /cm3. A 73% electrical activation, 31% compensation and 146 meV ionization level have been obtained using a best-fit solution of the neutrality equation to Hall carrier data for the lowest concentration.

A technique of controlling growth gas flow rate for adjusting crystal resistivity is presented in this paper. The experimental results showed that high growth gas flow rate could affect SiC crystal resistivity remarkably. The SiC crystal resistivity would get higher and higher with increasing growth gas flow rate. The purifying effect of gas flow rate was contributing to resistivity increase at a relatively low flow rate range. As for the high gas flow rate, increase of resistivity might be explained by the well-known site competition effect. Then, one explanation for reducing nitrogen content in the crystal via increasing gas flow rate was put forward. Namely, the Si component in the gas species may more easily go through the graphite crucible at the initial stage to make the growth ambient C-rich when the gas flow rate is ∼800 sccm or more and hence suppress nitrogen incorporation into carbon site to increase crystal resistivity. This result is very helpful to grow high purity high resistivity SiC ingots.

Using metal-oxide-semiconductor devices, we show that the density of interface states at the SiO2/4H–SiC interface can be reduced by applying a N2 heat treatment to a silicon carbide (SiC) surface prior to the deposition of a gate dielectric. Remarkably, this technique yields an interface that is at least as good as the one formed by thermal oxidation in terms of electrically active defects. This improvement can be traced to nitrogen insertion at the semiconductor surface, which provides a seed layer for subsequent deposition. The nature of N incorporation and its impact on electrical properties were studied using x-ray photoelectron spectroscopy, secondary ion mass spectroscopy, and capacitance-voltage measurements. These results offer a new perspective in the quest to maximize minority carrier mobility and minimize energy loss in 4H–SiC switches.

Highly efficient polytype 4H silicon carbide (4H-SiC) p–n diodes for ultraviolet (UV) light detection have been fabricated, characterized, and exposed to high-intensity mercury lamp irradiation (up to 17 mW/cm2). The behavior of the photocurrent response under UV light irradiation using a low-pressure mercury UV-C lamp (4 mW/cm²) and a medium-pressure mercury discharge lamp (17 mW/cm²) has been studied. We report on long-term UV photoaging tests performed for up to 22 mo. Results demonstrate the robustness of SiC photodiodes against UV radiation. The devices under test showed an initial burn-in effect, i.e., the photocurrent response dropped by less than 5% within the first 40 h of artificial UV aging. Such burn-in effect under UV stress was also observed for previously available polytype 6H silicon carbide (6H–SiC) p–n photodetectors. After burn-in, no measurable degradation has been detected, which makes the devices excellent candidates for high irradiance UV detector applications.

In this work, the relationship between the substrate crystallinity and the on-state resistances of silicon carbide (SiC) photoconductive semiconductor switches (PCSSs) was investigated. PCSSs with different channel lengths were fabricated on semi insulating 6H–SiC having different crystal qualities. A method was introduced for determining the photoconductive capacity of the SiC PCSSs. The experimental data suggest that the photoconductive capacity decreases sharply with the degradation of the full width at half maximum of the rocking curve of the 6H–SiC substrates. It is found that increasing the carrier mobility is a key factor for reducing the on-state resistance of the 6H–SiC PCSSs. Moreover, the results in this work present reference for the selection of 6H–SiC substrates for the fabrication of PCSSs and some other photoelectric devices.

Fabrication of nanosized silicon carbide (SiC) crystals is a crucial step in many biomedical applications. Here we report an effective fabrication method of SiC nanocrystals based on simple electroless wet chemical etching of crystalline cubic SiC. Comparing an open reaction system with a closed reaction chamber, we found that the latter produces smaller nanoparticles (less than 8 nm diameter) with higher yield. Our samples show strong violet-blue emission in the 410–450 nm region depending on the solvents used and the size. Infrared measurements unraveled that the surface of the fabricated nanoparticles is rich in oxidized carbon. This may open an opportunity to use standard chemistry methods for further biological functionalization of such nanoparticles.

A method of growing SiC nanowires (NWs) on 4H–SiC surfaces by in situ vapor-phase catalyst delivery was developed as an alternative to the ex situ deposition of the metal catalyst on the targeted surfaces before the NW chemical vapor deposition (CVD) growth. In the proposed method, sublimation of the catalyst from a metal source placed in the hot zone of the CVD reactor, followed by condensation of the catalyst-rich vapor on bare substrate surface was used to form the catalyst nanoparticles required for the vapor–liquid–solid (VLS) growth of SiC NWs. The NW density was found to gradually decrease downstream from the catalyst source and was influenced by both the gas flow rate and by the catalyst diffusion through the boundary layer above the catalyst source. Formation of poly-Si islands at too low value of the C/Si ratio created preferential nucleation centers for misaligned SiC NWs and NW bushes. The flexibility of controlling the nanoparticle density made this technique suitable for NW growth on horizontal surfaces as well as on patterned SiC substrates, including the vertical sidewalls of SiC mesas.

SiC nanowires (NWs) designed from selected bulk polytypes are investigated using quantum mechanics-based simulations (both ab initio and semiempirical methods), and their structure–property relationships examined vis-à-vis their size, shape, and orientation. It is found that 2H–SiC NWs of hexagonal morphology oriented along the <0001> direction are the most stable ones compared to NWs designed using other bulk polytypes (e.g., 3C, 4H, or 6H) and other morphologies (round, square, rhombus, etc.) for diameters with 1 nm < d < 14 nm. Based on the electronic density calculations, it is found that 2H–SiC <0001> NWs exhibit semiconductor-like characteristics (akin to their bulk counterparts), even when their diameters approach 1 nm. On the other hand, SiC NWs designed from 3C, 4H, and 6H bulk polytypes, regardless of their morphology, exhibit gapless features for diameters less than 3.5 nm. Undoubtedly, these novel properties of SiC NWs can be exploited in the fabrication of nanoscale devices.

A functionalization method for the specific and selective immobilization of the streptavidin (SA) protein on semiconductor nanowires (NWs) was developed. Silicon (Si) and silicon carbide (SiC) NWs were functionalized with 3-aminopropyltriethoxysilane (APTES) and subsequently biotinylated for the conjugation of SA. Existence of a thin native oxide shell on both Si and SiC NWs enabled efficient binding of APTES with the successive attachment of biotin and SA as was confirmed with x-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and atomic force microscopy. Fluorescence microscopy demonstrated nonspecific, electrostatic binding of the SA and the bovine serum albumin (BSA) proteins to APTES-coated NWs. Inhibition of nonspecific BSA binding and enhancement of selective SA binding were achieved on biotinylated NWs. The biofunctionalized NWs have the potential to be used as biosensing platforms for the specific and selective detection of proteins.

In this article, the biofunctionalization of 6H–SiC (0001) surfaces via self-assembled monolayers (SAMs) has been studied as a means to modify the in vitro biocompatibility of this semiconductor substrate with H4 (human neuroglioma) and PC12 (rat pheochromocytoma) cells. Silanization with aminopropyldiethoxymethylsilane (APDEMS) and aminopropyltriethoxysilane (APTES), which provided moderately hydrophilic surfaces, and alkylation with 1-octadecene that produced hydrophobic surfaces were used to control the 6H–SiC surface chemistry and evaluate changes in cell viability and morphology due to these surface modifications. The morphology of the cells was evaluated with atomic force microscopy. In addition, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays were used to quantitatively evaluate the cell viability on the SAM-modified surfaces. In all cases, the cell proliferation was observed to improve with respect to untreated 6H–SiC surfaces, with up to a 2x increase in viability on the 1-octadecene-modified surfaces, up to 6x increase with APDEMS-modified surfaces, and up to 8x increase with APTES-modified surfaces. This proves the potential of SiC as a substrate for medical devices given the possibility to tailor its surface chemistry for specific applications.

Silicon carbide (SiC) detectors were used to analyze the multi-MeV ions of the plasma produced by irradiation of various targets with a 300-ps laser at intensity of 1016 W/cm2. The SiC detectors were realized by fabricating Schottky diodes on 80 μm epitaxial layer. The low dopant concentration and defect density of the epilayer allowed the realization of good performance detectors. The use of SiC detectors ensures the cutting of the visible and soft ultraviolet radiation emitted from plasma enhancing the sensitivity to very fast ions. The time-of-flight spectra obtained by irradiating different targets show a peak associated to protons and various peaks relative to different charge states of ions. Processing of the experimental data allows to estimate the energies of the protons and of the different ions emitted from laser-induced plasma. The SiC detector results are compared with the ones obtained by Ion Collector and a Thomson Parabola spectrometer.

Development of 3C–SiC-based electronics is hampered by film quality and wafer bow produced during growth on silicon. This work presents an approach aimed to improve the compliance between Si and 3C–SiC by manipulating Si substrate surface with the creation of an array of squared-base Inverted Silicon Pyramids (ISP) and stimulating the annihilation of defects created at the interface. A reduction of stacking fault (SF) linear density to a value of 9.31 × 103 cm−1 has been observed in 9-μm-thick 3C–SiC film on ISP, stimulated by the ISP geometry with SFs forced to meet one another within the first micrometer of growth. The initial growth of 3C–SiC on ISP is described suggesting a peculiar growth mode leading to uniform sample morphology after about 3 μm of growth. Finally, lower residual stress stored in 3C–SiC/ISP samples has been observed, due to a faster stress relaxation mechanism during the film growth.

In this article we develop an analytical theory that correlates the macroscopic curvature of stressed film/substrate systems with the microscopic in-plane and out-of-plane deflections of planar rotators. We have extended these stress-deflection relations in the case of nonlinear stress fields and validated the results with the aid of finite element simulations. We use this theory to study the heteroepitaxial growth of cubic silicon carbide on silicon (100) and discovered that, due to defects generated on the silicon substrate during the carbonization process, wafer curvature techniques alone may not enable determination of the stress field in the grown films either quantitatively or qualitatively.

Ultrathin SiC buffer layers have been grown on Si (100) substrates by atmospheric pressure chemical vapor deposition. The evolution of buffer layer morphological properties as a function of carbonization parameters is investigated by atomic force microscopy. Based on the quantitative analysis of the dependences of void density, void depth, void width, and surface roughness on carbonization parameters, a buffer layer growth model is proposed, and the effects of carbonization parameters on buffer layer morphology are clarified. The void density is related to the carbonization temperature, temperature ramp-up rate, and C3H8 concentration by affecting the initial SiC nuclei density. The void size is evolved with processing time and mainly dependent on the carbonization temperature but slightly affected by C3H8 and H2. The buffer layer morphology is deteriorated with increasing H2 flow rate when the C3H8 concentration is fixed.

To overcome the low fabrication yield associated with single crystalline 3C–SiC diaphragm-based high temperature capacitive pressure sensors fabricated by wafer bonding, we have developed an alternative based on a polycrystalline SiC-on-Si architecture. The capacitive pressure sensing element, i.e., a thin film diaphragm, was fabricated using low stress and high conductivity low-pressure chemical vapor deposition poly-SiC thin films, and the sensing architecture was formed by wafer bonding a poly-SiC film to a Si substrate using phosphosilicate glass bonding films. With a geometric aspect ratio of up to 800:1 and a maximum deflection load eight times or more to their thickness, the poly-SiC diaphragm-based sensors presented repeatable pressure sensing characteristics up to 500 °C.

To understand the impact that the growth rate has on the residual stress of chemical vapor deposition-grown 3C–SiC heteroepitaxial films on Si substrates, growth experiments were performed. The film thickness was held constant at ∼2.5 μm independent of the growth rate so as to allow for direct film comparison as a function of the growth rate. Stress analysis performed by profilometer curvature measurement, μιχρο-Raman shift analysis and micro-machined freestanding structures, show an apparent disagreement about the stress nature. This incongruity between the experimental data can be explained assuming a strong stress field located in the substrate related to defects generated in the silicon during the growth process.

Next-generation fission and fusion nuclear reactor materials will be exposed to very high temperatures, intense neutron radiation, corrosive environments, and, mostly, all three at once. Grand opening will be given to the material, if they have stability at high temperature operating favorable in the extreme environments, self-healing, thermal as well as irradiation properties. Owing to the superior properties of silicon carbide, nuclear scientists are closely evaluating SiC-based materials for various applications in nuclear reactors. In the present perspective, relevant properties, challenging issues, and recommendations are emphasized. Based on our recent experiments, attempt to solve various uses on SiC-based materials in nuclear applications is described in detail.