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Tungsten targets were first irradiated with high energy W6+ ions (20 MeV) with different dose rates at 800 K and then loaded with deuterium at room temperature to decorate the displacement damage created in the first step. Detailed microstructure investigations were performed and compared with calculated damage profiles and deuterium depth profiles to link defect characteristics with the ability to retain hydrogen isotopes. Results directly indicate that depending on the used dose rate dislocation density and characteristics change. However, deuterium retention does not. Thus, we conclude that overall dislocation density does not affect deuterium retention significantly. Changes in D retention were observed as function of the depth of the damaged zone. Variations of dislocation density were also depth dependent. Consequently, we link changes in D retention with the dislocation presence, number of implanted tungsten ions and other point defects. The latter seem to affects D retention the most.

The precipitation behavior of Y2O3 and MnO nanoparticles after isothermal treatment, in a Ni-free N-containing oxide dispersion strengthened (ODS) steel was studied by wide-angle X-ray scattering (WAXS), ultra-small-angle and small-angle X-ray scattering (USAXS/SAXS), small angle neutron scattering (SANS) and scanning transmission electron microscopy (STEM). Mechanical properties were investigated via tensile and micro-hardness testing. Additional precipitation occurred during annealing, in addition to the precipitates formed during sintering. The highest volume distribution of Y2O3, with average size of 6 nm, was determined by alloy contrast variation (ACV) analysis of SAXS and SANS for the sample annealed at 800 °C; this sample shows the highest hardness and ultimate tensile strength. Above that temperature, coarsening of both matrix and precipitates and depletion of nitrogen from matrix degraded the mechanical properties. The very fine nanoparticles and thermally induced dissolution of nitrogen influenced mechanical properties.

In order to fabricate the AlGaN/GaN-on-Si HEMTs on existing Si-CMOS production lines, manufacturing processes must meet the rigors of Si-CMOS technology eliminating Au. One of the requirements is formation of Au-free, low resistivity ohmic contacts to AlGaN/GaN heterostructures. In this work we report structural and electrical studies of Ti/Al-based ohmic contacts to AlGaN/GaN HEMTs with TiN/Cu cover layers. Ohmic contacts have been observed after annealing of Ti/Al/TiN/Cu or Ti/Al/Ti/TiN/Cu/TiN multilayers on recessed AlGaN/GaN structure at temperature of 550 °C, specific contact resistance is about 2.3 × 10−4 Ω cm2, however, lower value was obtained after annealing at 750 °C. The XRD and TEM studies reveal formation of additional phases during annealing, namely Al3Ti and Ti2AlN inside the volume of the metallization stack and AlN at metal/GaN interface. Measured dependence of contact resistance on temperature suggests a “metal-like” carrier transport mechanism in partially recessed Ti/Al/Ti/TiN/Cu ohmic contact to 2D electron gas.

Tungsten targets have been self-damaged with 20 MeV W6+ ions followed by decoration of defects with deuterium and 500 keV helium implantation. Such treatment creates a significant amount of irradiation-induced defects which depend on the distance from the surface. As a final step, selected samples were annealed at 1700 K for 30 min to study defect evolution at high temperature. Detailed TEM analysis, supported with quantification of microstructure, provided an insight into the effect of helium implantation on the previously established dislocation structure and its thermal stability. It was shown that helium is implanted into the material down to approximately 900 nm from the surface and creates a locally enhanced dislocation density which remained stable even after high temperature annealing. This phenomenon is opposite to annihilation of dislocations observed in the sample without helium treatment. At the same time, helium implanted zone is the source of internal stress fields which cover the whole irradiated depth. Thermal treatment releases lattice from this stress. The possible reasons of these occurrences are discussed in the light of helium interactions with vacancies and self-interstitials in the presence of dislocations which directly impacts hydrogen isotopes retention.

The final shut-down of Tokamak Experiment for Technology Oriented Research in year 2013 created unique opportunities for multi-directional studies of in-vessel components. A set of specimens from t ...