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Single-event burnout and single-event leakage current (SELC) in silicon carbide (SiC) power devices induced by heavy ions severely limit their space application, and the underlying mechanism is still unclear. One fundamental problem is lack of high-resolution characterization of radiation damage in the irradiated SiC power devices, which is a crucial indicator of the related mechanism. In this Letter, high-resolution transmission electron microscopy (TEM) was used to characterize the radiation damage in the 1437.6 MeV 181Ta-irradiated SiC junction barrier Schottky diode under 200 V. The amorphous radiation damage with about 52 nm in diameter and 121 nm in length at the Schottky metal (Ti)–semiconductor (SiC) interface was observed. More importantly, in the damage site the atomic mixing of Ti, Si, and C was identified by electron energy loss spectroscopy and high-angle annular dark-field scanning TEM. It indicates that the melting of the Ti–SiC interface induced by localized Joule's heating is responsible for the amorphization and the possible formation of titanium silicide, titanium carbide, or ternary phases. The mushroom-like hillock in the Ti layer can be attributed to Rayleigh–Taylor instability, as another evidence for ever-happened localized melting near the Schottky interface. These modifications at nanoscale in turn cause localized degradation of the Schottky contact, resulting in permanent increase in leakage current. This experimental study provides very valuable clues for a thorough understanding of the SELC mechanism in SiC diodes. [ABSTRACT FROM AUTHOR]

Besides radiation resistance, thermal recovery of radiation damage provides another critical criterion to evaluate the host phase for immobilizing high-level waste (HLW) produced by nuclear plants. Despite the increasing investigations, a comprehensive atomic-scale understanding remains elusive on thermal annealing of radiation damage in ceramics. Here, using in situ heating high-resolution transmission electron microscopy, we investigate the thermal annealing of radiation damage in natural metamict titanite (CaTiSiO 5) caused by a high alpha decay dose from the incorporated U and Th during the geologic time. The recovery of the fully amorphous titanite precursor starts at 456 ℃ from the appearances of monoclinic nanoparticles 2–5 nanometers wide, and more nanoparticles form as the temperature gradually increases. At 1000 ℃, the amorphous phase recovers through epitaxial growth with titanite nanoparticles as templates. This study provides information for a unit-cell-scale understanding of the thermal stability of radiation damage in titanite-based ceramics, having significance for immobilizing HLW. • Thermal recovery of totally amorphous titanite was investigated by in situ heating HRTEM. • The recovery of amorphous titanite starts from the appearance of nanoparticles. • The epitaxial growth with a titanite nanoparticle being the template was observed in real time. [ABSTRACT FROM AUTHOR]

Reidite, a high-pressure phase of zircon, is increasingly identified at terrestrial impact sites. Despite its growing recognition, the potential applications for estimating minimum impact pressure face impediments due to existing discrepancies in the condition of zircon-reidite transformation, controversial models governing the transformation mechanism, and unclear effects of pre-existing radiation damage on reidite formation. Here, we show enhanced reidite formation by synchrotron X-ray diffraction, Raman spectroscopy, and transmission electron microscopy analyses of zircon grains that have experienced different alpha-decay doses from U and Th impurities and subsequent pressurization in diamond anvil cells. Below ∼1 × 1018 α-decay events/g, the α-decay-induced isolated point defects in the still crystalline zircon facilitate the minor atomic readjustments required for reidite formation. However, above this dose, the loss of long-range periodicity in severely damaged or even metamict zircon inhibits the transformation. The enhanced reidite formation by minor radiation damage coincides with the more common occurrence of reidite at impact sites for which the precursor zircon has a relatively lower alpha-decay-event dose before the impact event. In addition, the detailed atomic-scale structures of twinned reidite provide unambiguous evidence for a characteristic internal stress-induced martensitic transition. These findings have important implications for interpreting the formation conditions of natural reidite due to the convergence of pressure from the static, shockwave, and natural reidite samples. • Moderate radiation damage enhances atomic adjustments for reidite formation. • Reidite preferentially occurs in craters with moderately damaged zircon. • Static, shocked, and natural reidite have similar formation mechanisms. • Atomic scale twinned reidite suggests internal stress-assisted martensitic transition. • Constraining the minimum impact pressure should consider radiation damage. [ABSTRACT FROM AUTHOR]

The effect of defects on the high‐pressure behavior of materials is fundamental to understanding and designing materials for extreme environments. Previous work has demonstrated that radiation damage can enhance phase stability or alter the transformation pathway. Here, we report the high‐pressure phase stability of CeO2 irradiated by swift heavy ions. CeO2 is of particular interest because it can be used as a non‐radioactive surrogate for UO2 and PuO2. High‐pressure Raman spectroscopy shows that low‐fluence ion irradiated CeO2 exhibits nearly the same high‐pressure behavior as unirradiated CeO2; whereas, after high‐fluence irradiation, the phase stability of CeO2 is significantly enhanced, with the critical phase transition pressure increased from 31.7 to 37.3 GPa and only about 7% high‐pressure phase transition fraction at 45.1 GPa. In comparison with the high‐pressure Raman results of pre‐irradiated CeO2 before and after 573, 1073, and 1 273 K annealing in air, we propose that large interstitial‐type defect clusters, such as dislocation loops formed in heavily‐irradiated CeO2, are predominately responsible for the increased phase stability at high pressures. [ABSTRACT FROM AUTHOR]