Deuterium retention and transport in ion-irradiated tungsten exposed to deuterium atoms: role of grain boundaries

The influence of grain boundaries on deuterium (D) retention and transport was investigated in nanocrystalline tungsten (W) by exposing the samples to sub eV D atoms. Thin tungsten films with nanometer-sized grains were produced by pulsed laser deposition on tungsten substrates. Their grain size was increased up to one micrometer by thermal annealing in vacuum up to 1223 K. Irradiation damage was created by 20 MeV W ions at 290 K. The transmission electron microscopy analysis showed one order of magnitude larger dislocation density in nanometer-grained samples compared with the larger-grained samples. The samples were after W irradiation exposed to 0.3 eV D atoms at 600 K. D retention and D depth profiles were measured by nuclear reaction analysis. In the as-deposited nanometer-grained samples, D populated the damaged region more than three times faster than in the samples with larger grains, indicating that grain-boundaries increase D transport through the material. The concentration of defects was assessed by the final D concentration in the samples. The sample with the smallest grain size showed slightly larger D concentration in the irradiated area, but the difference in the D concentration was not substantial between different-grained samples. A large D concentration in the non-irradiated nanometer-grained sample was measured which is an indication for a high defect density in the initial material. From our observations, it can be postulated that the nanocrystalline microstructure did not substantially influence the generation of irradiation-induced defects by defect annihilation at grain boundaries

First study of the location of deuterium in displacement-damaged tungsten by nuclear reaction analysis in channeling configuration

Nuclear reaction analysis (NRA-C) together with Rutherford backscattering spectrometry (RBS-C), both in a channeling configuration were used to study the location of deuterium (D) in irradiation-induced defects in tungsten (W) using a 3He probe beam. The defects were created by W ion irradiation at two different damage doses of 0.02 and 0.2 dpa and two temperatures of 290 K and 800 K. Angular scans over the 〈100〉 axial channel showed that for both 800 K irradiated samples the NRA yield peaks in the centre of the channel, where the RBS is at its minimum. For the room-temperature-irradiated samples this is only true for the low dose. For the high dose sample hardly any peak is observed. 2D channeling maps were recorded for the samples damaged to 0.02 dpa at 290 K and 0.2 dpa at 800 K. They show in addition to the maximum D signal in the 〈100〉 axial channel increased intensity in a (110) planar channel where the RBS intensities are low. The software algorithm RBSADEC was used to investigate the location of the D in the lattice. A first comparison of simulation and experiment suggests that D is located close to tetrahedral sites

Effects of Irradiation on Porous Silicon

Besides the well-known effect of photoluminescence, the impinging of photons and other kinds of particles such as electrons, ions, and muons on porous silicon produces important effects. Some of these effects can modify the structure and properties of the material, distorting the interpretation of data based on the use of irradiation. Some of the irradiation effects are useful in different applications such as photodynamic therapy or display applications. This work is a review of the effects of irradiation on porous silicon.Fil: Koropecki, Roberto Roman. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Física del Litoral. Universidad Nacional del Litoral. Instituto de Física del Litoral; ArgentinaFil: Arce, Roberto Delio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Física del Litoral. Universidad Nacional del Litoral. Instituto de Física del Litoral; Argentin