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In this study, the effect of swift heavy ions (SHIs) irradiation in the recrystallization of polycrystalline SiC pre-implanted with selenium (Se) ions and migration of Se was investigated. The main objective of this study is to investigate the role of SHIs with the maximum electronic energy loss greater than 20 keV/nm on structural evolution of initially amorphized pre-implanted SiC and the migration of pre-implanted fission products (FPs). The pristine SiC samples were first implanted with 200 keV Se ions to a fluence of 1 × 1016 cm−2 at room temperature (RT) and at 350 °C. Some of the pre-implanted samples were then irradiated with bismuth (Bi) ions of 710 MeV to a fluence of 1 × 1013 cm−2 at RT. The characterization of both the implanted and implanted then irradiated SiC was conducted using techniques such as transmission electron microscopy (TEM), Raman spectroscopy, scanning electron microscopy (SEM), and Rutherford backscattering spectrometry (RBS). At RT, Se ions implantation caused the amorphization of SiC to a depth of about 187 nm beneath the surface. In contrast, when implanted at 350 °C, the SiC retained its crystalline structure with some defects (i.e., point defects, point defect clusters and some dislocation loops). The SHIs irradiation of the RT implanted SiC resulted in the reduction of the amorphous layer thickness from 187 nm to around 178 nm and led to the formation of nanocrystalline SiC in the amorphous layer. Irradiation of the SiC implanted at 350 °C induced some crystallization of defects. Notably, no evidence of Se ions migration was observed in both the irradiated RT-implanted and the hot-implanted SiC. • Polycrystalline SiC substrates were implanted with Se ions of 200 keV to a fluence of 1 × 1016 cm−2 at room temperature (RT) and 350 °C, subsequently some samples were irradiated with710 MeV Bi+51 (maximum electronic energy loss of 33.7 keV/nm) to fluence of 1 × 1013 cm−2 at RT. • At RT, the implantation of the ions caused amorphization in SiC, whereas implantation at 350 °C maintained its crystalline structure with some defects. • The SHIs irradiation of RT pre-implanted SiC led to the formation of nanocrystalline SiC in the amorphous layer. While irradiation of the SiC implanted at 350 °C induced some crystallization of defects. • There was no migration of the implanted Se ions was detected after exposing both RT and 350 °C pre-implanted SiC to 710 MeV Bi+51 irradiation with maximum electronic energy loss of about 33.7 keV/nm. [ABSTRACT FROM AUTHOR]

Abstract Recent work has shown that electronic excitations play a role in the creation of optical point defects in AlN although the material had been considered during a long time as insensitive to electronic energy loss and radiolysis. We address here an indirect observation of the effect of electronic excitations on point defect in AlN. Unprecedented climb of screw dislocations under swift heavy irradiation in irradiated AlN is studied. This is a sign to point defect diffusion towards the dislocation, which allows the increase of the length of the dislocation line. It is demonstrated that the climb, thus the point defect creation and/or their mobility is mainly induced by electronic excitations. This happens above an electronic stopping power threshold much lower than the one for ion track formation in AlN. This climb of dislocation was also observed for the same irradiation conditions in Al x Ga 1−x N (x = 0.5; 0.7; 0.8). [ABSTRACT FROM AUTHOR]

In this work, GaN epilayers, grown on (0 0 0 1) sapphire substrate, were studied under swift heavy ion irradiation with a broad variety of projectiles at different energies. Several characterization techniques including transmission electron microscopy, optical absorption spectroscopy and Raman scattering spectroscopy, employed for different irradiation conditions, allowed the identification and the attribution of the origin of the observed modifications. It has been established that for projectiles presenting an electronic stopping power higher than a threshold of 17 keV.nm −1 , there was the formation of disordered latent tracks on the ion paths. We have shown that these tracks become more continuous and are visible until a higher depth with the increase of the projectile electronic stopping power. We have also highlighted that the latent tracks induce the appearance of a biaxial stress of the order of some GPa and strongly modify the optical bandgap values. Contrary to this effect of electronic energy loss, the atomic displacements generated by nuclear energy loss process did not imply significant biaxial stress and optical bandgap closing. [ABSTRACT FROM AUTHOR]

AlN, GaN, and InN were irradiated at room temperature with monatomic swift heavy ions and high-energy fullerenes. Ion track formation was studied using transmission electron microscopy in both plane view and cross-sectional modes. A full experimental description of ion track formation in these compounds is presented. AlN shows a remarkable resistance towards track formation; InN is the most sensitive and shows partial decomposition, likely into N and metallic clusters; the overlapping of the amorphous tracks in GaN does not give an amorphous layer because of a track-induced recrystallization. We discuss the application of the inelastic thermal spike model, which allows good and simple predictions of track radii in oxides, to the studied III-nitrides, and in general to semiconductors. [ABSTRACT FROM AUTHOR]

This paper details in-situ studies of modifications induced by swift heavy ion irradiation in α-Al2O3. This complex behaviour is intermediary between the behaviour of amorphizable and non-amorphizable materials, respectively. A unique combination of irradiation experiments was performed at the IRRSUD beam line of the GANIL facility, with three different characterisation techniques: in-situ UV–Vis absorption, in-situ grazing incidence X-Ray diffraction and ex-situ transmission electron microscopy. This allows a complete study of point defects, and by depth profile of structural and microstructural modifications created on the trajectory of the incident ion. The α-Al2O3 crystals have been irradiated by 92 MeV Xenon and 74 MeV Krypton ions, the irradiation conditions have been chosen rather similar with an energy range where the ratio between electronic and nuclear stopping power changes dramatically as function of depth penetration. The main contribution of electronic excitation, above the threshold for track formation, is present beneath the surface to finally get almost only elastic collisions at the end of the projected range. Amorphization kinetics by the overlapping of multiple ion tracks is observed. In the crystalline matrix, long range strains, unit-cell swelling, local microstrain, domain size decrease, disordering of oxygen sublattice as well as colour centre formation are found. This study highlights the relationship between ion energy losses into a material and its response. While amorphization requires electronic stopping values above a certain threshold, point defects are predominantly induced by elastic collisions, while some structural modifications of the crystalline matrix, such as unit-cell swelling, are due to contribution of both electronic and nuclear processes. [ABSTRACT FROM AUTHOR]

In this work, Al x Ga 1 − x N ( x = 0; 0.1; 0.3; 0.5; 0.65; 0.7; 0.8; 1) wurtzite epilayers, grown on c-plane sapphire substrates, have been irradiated with Swift Heavy Ions at GANIL facility. Modifications induced by irradiation are characterized with in-situ optical absorption spectroscopy at 15 K. Spectra of these irradiated alloys exhibit optical absorption band formation, related to new energy levels in their bandgaps, whose positions only depend on the composition of the layer. However, these absorption bands are not observed in the Al x Ga 1 − x N with Al molar fraction less than 0.3, likely because the energy level of the corresponding defect is located above the conduction band. Moreover, using different irradiation conditions, a coupled effect between nuclear collisions and electronic excitations for these color center creation have been investigated. A synergy between these two phenomena has been shown and appears to be independent of the composition of the alloy. [ABSTRACT FROM AUTHOR]