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1.
The high-energy part of the blue fluorescence of-SiC(6H) is found to be dependent on the nitrogen (donor) concentration. The line fluorescence spectrum is found to include a new series of lines due to radiative transitions to A1 acceptor levels.We are indebted to J.G. Pichugin for providing the crystals.  相似文献   

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There has been some question as whether micropipes in SiC crystals, giant dislocations that possess hollow cores and lie roughly along the hexagonal c-direction, are screw dislocations with Burgers vectors of nc, where n is an integer, or are dislocations of mixed character, with Burgers vector nc?+?ma, where m is equal to n or possibly different from n. X-ray topographs of the basal faces of PVT-grown 4H-SiC wafers containing micropipes taken in both back-reflection and grazing-incidence geometries are compared with computer simulations of micropipe images. The deviation from circular symmetry of micropipe images in such topographs may be explained as well by the micropipe's tilt from the c-direction as by an nc?+?ma nature. The contrast of micropipes in electron micrographs comprises of a pair of light and dark lobes consisting of a detailed system of subsidiary fringes. These are comparable with micropipe image computer simulations for Burgers vector nc. When an na edge component is introduced to the simulation, a small feature, a few hundred nm wide, appears, which is absent from the micrographs.  相似文献   

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Cubic-silicon carbide crystals have been grown from carbon-rich silicon solutions using the travelling-zone method. To improve the growth process, we investigated the effect of controlling more tightly some of the growth parameters. Using such improved growth conditions, our best sample is a 12 mm diameter and 3 mm long 3C–SiC crystal. It is grown on a (0001) 2 off, 6H–SiC seed and has 111-orientation. The low amount of silicon inclusions results in a reduced internal stress, which is demonstrated by the consideration of μ-Raman spectra collected at room temperature on a large number of samples.  相似文献   

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The infrared luminescence of Er3+ ions has been studied in bulk crystals of silicon carbide 6H-SiC doped with erbium in the process of their growth. The erbium centers of different symmetry in the crystals are revealed by the EPR technique. A number of intense luminescence bands of erbium ions are observed at a wavelength of about 1.54 μm. The luminescence can be excited by the light with quantum energies above and below the band gap of SiC. It is found that the luminescence exhibits unusual temperature behavior: as the temperature increases, the luminescence intensity abruptly rises starting with 77 K, passes through a maximum at ∼240 K, and, in the vicinity of ∼400 K, decreases down to the values observed at 77 K. The activation energies for the flare-up and quenching of the Er3+ luminescence are estimated at E A ≈130 and ≈350 meV, respectively. The mechanisms of the flare-up and quenching of the Er3+ luminescence in SiC are discussed. __________ Translated from Fizika Tverdogo Tela, Vol. 42, No. 5, 2000, pp. 809–815. Original Russian Text Copyright ? 2000 by Babunts, Vetrov, Il’in, Mokhov, Romanov, Khramtsov, Baranov.  相似文献   

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Erbium ions have been incorporated for the first time in bulk 6H-SiC crystals during growth, and they were unambiguously identified from the 167Er EPR hyperfine structure. High-temperature luminescence of erbium ions at a wavelength of 1.54 μm has been detected. The observed luminescence exhibits an increase in intensity with increasing temperature. The observation of Er luminescence in 6H-SiC offers a promising potential for development of semiconductor light-emitting devices at a wavelength within the fiber-optics transparency window. Fiz. Tverd. Tela (St. Petersburg) 41, 38–40 (January 1999)  相似文献   

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Experiments are described which show that under pulsed thermal loading conditions, a damaged layer is formed in SiC which inherits the typical erosion defects (craters, chips, microcracks). Zh. Tekh. Fiz. 68, 133–135 (July 1998)  相似文献   

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The paper presents the results of optically detected magnetic resonance (ODMR) study of tunneling and photostimulated recombination processes in irradiated ionic crystals, observation of resonance effects using optically pumped F-centres, and investigation of spin-dependent recombination processes in silicon carbide doped with boron, aluminium, gallium and scandium.  相似文献   

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Photoluminescent (PL) p-type 6H porous silicon carbides (PSCs), which showed a strong blue-green photoluminescence band centered at approximately 490 nm, were annealed in Ar and vacuum conditions. The morphological, optical, and chemical states after annealing are reported on electrochemically etched SiC semiconductors.The thermal treatments in the Ar and vacuum environments showed different trends in the PL spectra of the PSC. In particular, in the case of annealing in a vacuum, the PL spectra showed both a weak red PL peak near 630 nm and a relatively intense PL peak at around 430 nm in the violet region. SEM images showed that the etched surface had spherical nanostructures, mesostructures, and islands. With increasing annealing temperature it changes all spherical nanostructures. The average pore size observed at the surface of the PSC before annealing was of the order of approximately 10 nm.In order to investigate the surface of a series of samples in detail, both the detection of a particular chemical species and the electronic environments at the surface are examined using X-ray photoelectron spectroscopy (XPS). The chemical states from each XPS spectrum depend differently before and after annealing the surface at various temperatures. From these results, the PL spectra could be attributed not only to the quantum size effects but also to the oxide state.  相似文献   

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《Physics letters. A》2020,384(5):126120
Thermal conductivity κ of 4H-, 6H-SiC and wurtzite GaN, InN, AlN crystals is calculated accounting phonon focusing effect at low temperatures with only diffusive phonon boundary scattering. The orientation dependence of thermal conductivity is similar in these materials. Thermal conductivity is enhanced in the direction of approximately 45 to the c axis up to 27% for GaN, 24% for 6H-SiC, 32% for InN, and 9% for AlN compared to the isotropic case for the circular cross-section and finite-length samples. Contributions of transverse T1 and T2 modes are nearly the same, about 40–45%, while the focusing of T2 mode contributes essentially to the angular dependence of κ. We find that the phonon focusing does not change κ value (within 5%) in the direction of 60 to the c axis in all hexagonal crystals studied so far.  相似文献   

14.
It is found that single crystals of silicon carbide exposed to soft X rays exhibit luminescence in the visible spectral range. The luminescence intensity from the single crystals produced by different methods differs by three-to fivefold. Also, the emission intensity is nonuniformly distributed over the single crystal surface, which may be related to the nonuniform distribution of impurities (activators).  相似文献   

15.
The thermopower coefficients of cubic bio-SiC, a high-porosity semiconductor with cellular pores prepared from the biocarbon template of white eucalyptus wood, and single-crystal β-SiC taken as a reference are measured in the temperature range 5–280 K. It is revealed that, in the low-temperature range, the samples are characterized by a thermopower contribution associated with the electron drag by phonons. The thermopower of the bio-SiC samples is measured both along and across the empty pore channels and is found to be anisotropic. Two models are proposed to account for the anisotropy of the thermopower in cubic bio-SiC.  相似文献   

16.
《Physics letters. A》2014,378(26-27):1897-1902
Spin-polarized density functional theory is used to study two-hydrogen defect complexes in silicon carbide. We find that the magnetism depends on the distances of the two hydrogen atoms. Magnetism appears when the two hydrogen defects are distant from each other, and magnetism cancels out if they are close to each other. The critical distance between the two hydrogen defects is determined.  相似文献   

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Planar dislocation pileups (PDPs) and curvilinear dislocation segments (CDSs) are considered as indicators of the local elastic shear stress fields (LESSFs) that existed in the growing single crystals at the time of stabilization of their dislocation structure. Calculations using the theory of dislocations with the experimental parameters of PDPs and CDSs measured from the x-ray topograms (taken by the Lang and divergent-polychromatic-beam (DPB) methods) give values of the LESSFs in the range (0.2–1.5)×106 Pa for thin single-crystal wafers of SiC (6H) grown by sublimation in a graphite container. A strong nonuniform bending of the single-crystal wafers is observed; for the x-ray topographic study of the dislocation structure in these wafers the DPB method is preferable to the Lang method on account of its low sensitivity to bending. Zh. Tekh. Fiz. 69, 64–67 (July 1999)  相似文献   

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Implanted muons in samples of silicon carbide have been observed to form paramagnetic muonium centers (μ + e). Muonium precession signals in low applied magnetic fields have been observed at 22 K in a granular sample of cubic β-SiC, however it was not possible to determine the hyperfine frequency. In a single crystal sample of hexagonal 6H-SiC, three apparently isotropic muonium states were observed at 20 K and two at 300 K, all with hyperfine frequencies intermediate between those of the isotropic muonium centers in diamond and silicon. No evidence was seen of an anisotropic muonium state analogous to the Mu* state in diamond and silicon.  相似文献   

19.
By the example of vanadium and erbium diffusion in porous silicon carbide, the semiconductor porous structure modification during thermal annealing has been simulated and the effect of this modification on impurity diffusion has been considered. A comparison of calculated and experimental profiles of the erbium and vanadium distributions in porous silicon carbide shows that the consideration of porous structure modification due to vacancy redistribution makes it possible to adequately describe diffusion in the porous semiconductor.  相似文献   

20.
Cu doped silicon carbide is shown to be ferromagnetic based on experiment results and first-principles calculations. The magnetization value of the Cu doped silicon carbide decreased as the Cu concentration increased. When the films were annealed at 800 °C, the ferromagnetic signal was increased. Reduction of the C vacancy concentration will introduce a large total moment in the system. Theoretically, compared with the case of one Cu atom replacing one Si atom, increasing the Cu doping, changing the Cu atom location or including carbon vacancies in the calculations for the system all make the ferromagnetic moment decrease. One Cu atom replacing one Si atom with the addition of one C vacancy makes the energy band gap of the system disappear. Our investigations suggest that the ferromagnetism arises from the hybridization between Cu 3d orbital and C 2p orbital. Ferromagnetic moment is influenced by a symmetry-lowering distortion of the surrounding lattice by the Cu dopant.  相似文献   

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