Damage In SiC Research Articles

Raman scattering as a probing method of subsurface damage in SiC

The subsurface damage extension has been investigated in 4H- and 6H-SiC as a function of the size of the polishing abrasive powder. Raman scattering spectra have been collected in the transverse ki//ks⊥c configuration and, from an analysis of the high-frequency longitudinal phonon–plasmon coupled mode, the free carrier density has been evaluated at different distances beneath the sample surface. It was found that the variation of the carrier density depends strongly on the size of the polishing slurry. Moreover, comparing 6H- and 4H-SiC it was found that, for a given slurry 4H-SiC damaged is deeper than 6H-SiC.

イオン注入ＳｉＣのパルスレーザーアニールとレーザー同時照射による低損傷イオン注入

In order to decrease the annealing temperature of ion-implanted SiC and reduce accumulated damage in SiC during ion implantation, a non-thermal-equilibrium annealing process using a pulsed excimer laser and simultaneous excimer laser annealing during ion implantation (SLII) were carried out. Laser annealed and SLII SiC were characterized by Rutherford backscattering channeling measurement. When 3, 000 shots and 30, 000 shots of laser irradiation were performed, the χ values of the N+ implanted SiC were suppressed from 89% before irradiation to 44% and 24%, respectively. When 30, 000 shots and 300, 000 shots of laser irradiation were performed, the x values of the Al+ implanted layers were suppressed from 64% before irradiation to 20% and 10%, respectively. Laser annealing brought good results in reducing the annealing temperature and suppressing damage in the ion-implanted SiC. Similarly, the χ values of the N+ implanted layer were decreased from 6365% to 3.55.7% by SLII. SLII also proved to be effective for suppressing implantation-induced damage in SiC.

Suppression of implantation-induced damage in 6H–SiC by simultaneous excimer laser irradiation during ion implantation

The implantation-induced damage suppression effect on 6H–SiC by simultaneous excimer laser irradiation during ion implantation (SLII) was demonstrated. A 308-nm XeCl excimer laser was used as the light source. Secondary ion mass spectroscopy indicated that SLII causes N atom diffusion in SiC. The damage suppression effect was evaluated by Rutherford backscattering channeling measurement. SLII proved to be effective for the suppression of implantation-induced damage in SiC. In the vicinity of the surface, SiC with almost no implantation-induced damage was obtained without postimplantation annealing.

Computer simulation of a 10 keV Si displacement cascade in SiC

The threshold energy for atomic displacement and the evolution of high-energy displacement cascades in β-SiC have been examined using molecular dynamics simulations. A modified form of the Tersoff potential was used in combination with a repulsive potential obtained from density functional theory to describe the interactions between the atoms. The evolution of lattice damage in a 10 keV Si cascade was studied for about 10 ps. The system size varied from 8000 atoms for the displacement energy calculations to 192,000 atoms for the cascade simulations. The results indicate that the minimum displacement energy is about 36 eV for Si and 28 eV for C. The cascade lifetime was found to be of the order of 0.1 ps, and the surviving C vacancies and interstitials outnumbered the corresponding Si defects by a factor of about 3. These results are discussed in light of previous theoretical and experimental studies of radiation damage in SiC.

X-ray diffractometry and high-resolution electron microscopy of neutron-irradiated SiC to a fluence of 1.9×10 27 n/m 2

Neutron-induced damage in SiC up to a fluence of 1.9×10 27 n/m 2 ( E>0.1 MeV) was examined by means of X-ray diffractometry and high-resolution electron microscopy. Specimens of β-SiC were irradiated in fast breeder reactors at 370 to 650°C. The lattice parameters of all specimens were increased by the irradiation, but above 2×10 26 n/m 2 lattice expansion decreased and was accompanied by significant peak broadening. Electron microscopy revealed a high density of interstitial loops on {111}, where X-ray diffraction peaks showed marked broadening. Peak broadening could be attributed mainly to the crystallite size effect at lower fluences, but a strain contribution was significant above 2×10 26 n/m 2. Electron diffraction patterns and high-resolution images indicated preservation of crystallinity up to the highest fluence observed. Thermal annealing up to 1000°C did not affect the peak broadening and average loop diameter. Above 1400°C, decrease in lattice strain and increase in crystallite size with increasing annealing temperature were observed.

Heavy ion fusion research in Spain

The indirect-direct illumination scheme has been investigated, and simulations were performed using the radiation-hydrodynamics code Sara, showing good agreement with experiments performed at CEL-V Limeil (France) in the PHEBUS laser. The use of an externally guided implosion of the fuel has been suggested, where two pellets, each being accelerated from opposite mouths of a cannon barrel, will collide and implode in a central cavity. A detailed opacity model ( Jimena-Dca) has been developed that treats absorption bands that result from many-particle configurations using the original Mozskowski's formalism; our average ion model ( Jimena-Ai) also includes that model. Frequency-dependent opacities for intermediate- and high- Z plasmas have been computed and tested through the WORKOP series. An adaptive mesh scheme has been implemented in the two-dimensional Arwen code based on an implicit Riemann solver and part of a Lagrangian flux-corrected transport staggered-mesh (RMFCT) scheme. The code can handle several materials on a Eulerian mesh, and includes simple ion and laser energy sources. A two-dimensional code for radiation-hydrodynamics ( Multi-2D) has been developed that uses non-structured triangular grids, and includes arbitrary Eulerian-Lagrangian hydrodynamics, radiation transport by discrete ordinates, and laser or heavy ion beam deposition. The inventory and radiological code ACAB has been extensively used to determine the activation in inertial fusion reactors and has been improved to include pulsed regimes and fission process. A molecular dynamics code has been developed in collaboration with LLNL to study neutron damage in SiC. DENIM is actively participating as one of the main proponents of the European Heavy Ion Ignition Facility of the European authorities, together with GSI Darmstadt, ENEA Frascatti and KfK Karlsruhe.

Thermal stability of dry etch damage in SiC

The introduction of dry etch damage into n-type SiC has been measured by monitoring the sheet resistance after exposure to Ar plasmas under both reactive ion etching and electron cyclotron resonance conditions. The threshold rf powers for measurable resistance changes in 1 μm thick films are ∼250 W for reactive ion etching (RIE) conditions, and ∼150 W for electron cyclotron resonance (ECR) conditions. A major annealing stage occurs with an activation energy of ∼3.4 eV, but some damage remains even after 1050 °C annealing.

Photothermal characterization of creep damage in SiC–SiO2

We demonstrate that ceramic composites with near surface damage may be characterized with photothermal methods in a noncontact, sensitive way through dependence on temperature. As an application we characterize a SiC–SiO2 composite with creep damage.

Comments on “considerations on PyC and SiC coated oxide particles for gas cooled fast reactor application” by M. Dalle Donne and G. Schumacher

Neutron-induced damage in SiC up to a fluence of 1.9×1027 n/m2 (E>0.1 MeV) was examined by means of X-ray diffractometry and high-resolution electron microscopy. Specimens of β-SiC were irradiated in fast breeder reactors at 370 to 650°C. The lattice parameters of all specimens were increased by the irradiation, but above 2×1026 n/m2 lattice expansion decreased and was accompanied by significant peak broadening. Electron microscopy revealed a high density of interstitial loops on {111}, where X-ray diffraction peaks showed marked broadening. Peak broadening could be attributed mainly to the crystallite size effect at lower fluences, but a strain contribution was significant above 2×1026 n/m2. Electron diffraction patterns and high-resolution images indicated preservation of crystallinity up to the highest fluence observed. Thermal annealing up to 1000°C did not affect the peak broadening and average loop diameter. Above 1400°C, decrease in lattice strain and increase in crystallite size with increasing annealing temperature were observed.

Radiation Damage in SiC

SiC has a band gap energy of about 2.9 ev; intrinsic SiC would be an excellent insulator at room temperature. In practice, the uncompensated room temperature resistivity of single crystal SiC rarely exceeds 100 Ω-cm. Information about radiation damage in SiC is scanty. Rates of charge carrier removal upon irradiation are similar to those found in Si. Most of the defects anneal at less than 8000C; within the operating range of some SiC devices. We have been interested principally in SiC p-n junctions, as rectifiers and as radiation detectors, and have studied their degradation in charged particle and neutron fluxes. Useful life is 1-100 times greater than can be achieved in comparable Si devices.