Disorder induced in silicon carbide by heavy-ion irradiation (original) (raw)
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Raman spectroscopy study of heavy-ion-irradiated α-SiC
Journal of Physics: Condensed Matter, 2006
Raman spectroscopy was used to investigate the structure of ion-irradiated α-SiC single crystals at room temperature and 400 • C. Irradiations induce a decrease of the Raman line intensities related to crystalline SiC, the appearance of several new Si-C vibration bands attributed to the breakdown of the Raman selection rules, and the formation of homonuclear bonds Si-Si and C-C within the SiC network. For low doses, the overall sp 3 bond structure and the chemical order may be almost completely conserved. By contrast, the amorphous state shows a strong randomization of the Si-Si, Si-C and C-C bonds. The relative Raman intensity decreases exponentially versus increasing dose due to the absorption of the irradiated layer. The total disorder follows a sigmoidal curve, which is well fitted by the direct impact/defect stimulated model. The chemical disorder expressed as the ratio of C-C bonds to Si-C bonds increases exponentially versus the dose. A clear correlation is established between the total disorder and the chemical disorder. The increase of temperature allows the stabilization of a disordered/distorted state and a limitation of damage accumulation owing to the enhancement of the dynamic annealing.
Behaviour of Nanocrystalline Silicon Carbide Under Low Energy Heavy Ion Irradiation
MRS Proceedings, 2009
Silicon carbide is one of the most studied materials for core components of the next generation of nuclear plants (Gen IV). In order to overcome its brittle properties, materials with nanometric grain size are considered. In spite of the growing interest for nano-structured materials, only few experiments deal with their behaviour under irradiation. To assess and predict their evolution under working conditions, it is important to characterize their microstructure and structure. To this purpose, we have studied microcrystalline and nanocrystalline samples before and after irradiation at room temperature with 4 MeV Au ions. In fact, it is well established that such irradiation conditions lead to amorphisation of the material, which can be restored after annealing at high temperature. We have performed isochronal annealings of both materials to point out the characteristics of the healing process and eventual differences related to the initial microstructure of the samples. To this pu...
Structural investigation of silicon carbide with micro-Raman spectroscopy
2009
Silicon carbide (SiC) is a suitable wide band gap semiconductor for high power and frequency electronic devices. The most important advantages of the material are good thermal conductivity and high breakdown voltage. Surface oxidation of SiC wafers results in forming of native SiO2 layer on the surface of the substrate. However, the material has significant drawbacks. The most important one for the application in electronic devices is the reduction of the carrier mobility by near interface traps (NIT's) [1]. The origin of the traps that are formed near the SiC / SiO2 interface is not clear. The possible defects which can play an important role in forming the traps are: defects formed in the vicinity of the SiC / SiO2 interface [1]; Si4C4-xO2 (x ≤ 2) structures [2, 3]; carbon structures (mainly graphitic [3, 4] or dimers [5]) placed at the interface SiC / SiO2; the structure of SiC layers placed in the vicinity of interface [2]; intrinsic oxide defects creating electronic states ...
Study of damage in ion-irradiated α-SiC by optical spectroscopy
Journal of Physics: Condensed Matter, 2006
UV-visible absorption and Raman scattering spectroscopy were used to investigate the effects of 4 MeV Xe-ion and 4 MeV Au-ion irradiations on α-SiC single crystals. The evolution of transmission spectra upon irradiation evidences an increase of the optical absorption. The optical band-gap energy decreases versus fluence, which is linked to band-gap closure attributed to the creation of localized states into the forbidden energy band. A strong effect of the irradiation temperature is observed as a result of dynamic annealing enhanced by the temperature increase. The Urbach energy increases versus fluence due to disorder accumulation in the damaged layer. Comparison of Urbach energy and disorder parameters extracted from Raman spectra shows that the Urbach energy is sensitive to the disorder induced by the accumulation of point defects.
Influence of ion energy on damage induced by Au-ion implantation in silicon carbide single crystals
Journal of Materials Science, 2011
Silicon carbide is an interesting material for GEN IV fission reactor projects because of its excellent properties. However, these properties will be altered under extreme conditions such as irradiation because of accumulation of damage. Mechanisms playing a role in defect formation require further studies in the case of high energy heavy ion irradiations. In this work a silicon carbide single crystal slice has been implanted with 20 MeV Au ions and probed by using Raman spectrometry. The resulting Raman spectra recorded as a function of depth clearly show a damaged zone, in which the width is in agreement with the projected range of the incident ions (R p ) calculated by using SRIM code. In this area, three damaged zones have been brought to light because of the high spatial resolution of the Raman spectrometry technique. The existence of these zones is discussed with regard to the different energy loss regimes of the implanted ions such as the electronic and nuclear ones.
Microstructural development in cubic silicon carbide during irradiation at elevated temperatures
Journal of Nuclear Materials, 2006
Microstructural development in chemically vapor-deposited (CVD) high-purity beta-SiC during neutron and self-ion irradiation at elevated temperatures was studied. The CVD SiC samples were examined by transmission electron microscopy following neutron irradiation to 4.5-7.7 • 10 25 n/m 2 (E > 0.1 MeV) at 300 and 800°C and 5.1 MeV Si 2+ ion irradiation up to 200dpaat600−1400°C.Theevolutionofvariousirradiation−produceddefectsincludingblackspotdefects,dislocationloops,networkdislocations,andcavitieswascharacterizedasafunctionofirradiationtemperatureandfluence.Itwasdemonstratedthattheblackspotdefectsandsmalldislocationloopscontinuetodominateatrelativelylowtemperatures(<200 dpa at 600-1400°C. The evolution of various irradiation-produced defects including black spot defects, dislocation loops, network dislocations, and cavities was characterized as a function of irradiation temperature and fluence. It was demonstrated that the black spot defects and small dislocation loops continue to dominate at relatively low temperatures (<200dpaat600−1400°C.Theevolutionofvariousirradiation−produceddefectsincludingblackspotdefects,dislocationloops,networkdislocations,andcavitieswascharacterizedasafunctionofirradiationtemperatureandfluence.Itwasdemonstratedthattheblackspotdefectsandsmalldislocationloopscontinuetodominateatrelativelylowtemperatures(<800°C), whereas they grow into Frank faulted loops and finally develop into dislocation networks at a higher temperature (1400°C). Substantial cavity formation on grain boundaries and stacking faults was confirmed after ion irradiation at 1400°C. These observations were discussed in relation with the known irradiation phenomena in SiC, such as low temperature swelling and cavity swelling.
Structural irradiation damage and recovery in nanometric silicon carbide
Progress in Nuclear Energy, 2012
Silicon carbide is one of the candidate materials for core components of some nuclear reactor projects (Gen-IV). In order to improve their thermo-mechanical properties, materials with nanometric grain size are considered. For such materials, nearly no data concerning their behaviour under irradiation are available. In this paper, we study the damage and subsequent recovery of a nanostructured 3CeSiC ceramic. Samples were irradiated at room temperature with 4 MeV Au ions and subsequently annealed. Their structural modifications are analysed with a grazing incidence X-ray diffraction method. Results show that these nanoceramic materials present the same damage kinetics during irradiation as conventional micrometric grained SiC, with total amorphisation at the highest fluence. However, while the recrystallisation of a conventional ceramic is expected to occur through an epitaxial recrystallisation from the non-damaged parts of the large grains, the nanometric material is healed only after annealing at 1000 C through mechanisms that can be attributed to a heterogeneous nucleation and growth of b crystallites in the totally amorphised grains.
Comparative Analysis of Defect Formation in Silicon Carbide under Electron and Proton Irradiation
Materials Science Forum, 2013
The irradiation with 0.9 MeV electrons and with 8 MeV and 15 MeV protons were performed for studying radiation defects. Proton scattering in a silicon carbide film has been numerically simulated. Distribution histograms of the energy imparted to recoil atoms are obtained. Two energy ranges are considered when analyzing the histograms. In the first range of "low" energies, individual Frenkel pairs with closely spaced components are created. In the second range, recoil atoms have energies sufficient for generating a cascade of displacements. This gives rise to microscopic regions with high density of vacancies and vacancy complexes of various kinds. All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, www.ttp.net. (ID: 194.85.224.35, Russian Academy of Sciences, St. Petersburg, Russian Federation-19/03/13,12:40:24)
Applied Physics A, 2018
At moderately elevated temperatures, radiation defects in SiC exhibit pronounced dynamic annealing, which remains poorly understood. Here, we study 3C-SiC bombarded at 100 • C with pulsed beams of 500 keV Ar ions. Radiation damage is monitored by a combination of X-ray diffraction, Raman scattering, and ion channeling. Similar damage buildup behavior but with different defect relaxation time constants, ranging from ∼ 1 to ∼ 6 ms, is observed for the different types of lattice defects probed by these techniques. A correlation between relaxation times and the nature of the defects is proposed. These results reveal additional complexity of radiation defect dynamics in SiC and demonstrate that results of different defect characterization techniques are needed for a better understanding of dynamic annealing processes in solids.
Optical spectroscopy study of damage induced in 4H-SiC by swift heavy ion irradiation
Journal of physics. Condensed matter : an Institute of Physics journal, 2012
Single crystals of 4H-SiC were irradiated with swift heavy ions (332 MeV Ti, 106 MeV Pb and 2.7 GeV U) in the electronic energy loss regime. The resulting damage was investigated with UV-visible optical absorption spectroscopy and micro-Raman spectroscopy. The evolution of the Raman data with fluence shows an accumulation of isolated point defects without amorphization of the material and a partial recrystallization of the structure, but only at the lowest fluence. Furthermore, the longitudinal optical phonon-plasmon coupling mode disappears upon irradiation, suggesting a strong perturbation of the electronic structure. This evolution is consistent with the optical bandgap decrease and the Urbach edge broadening that was also previously observed for the irradiation with 4 MeV Au ions.