| 1. |
- Dittrich, Laura, et al.
(författare)
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Impact of ion irradiation and film deposition on optical and fuel retention properties of Mo polycrystalline and single crystal mirrors
- 2023
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Ingår i: Nuclear Materials and Energy. - : Elsevier BV. - 2352-1791. ; 37
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Tidskriftsartikel (refereegranskat)abstract
- Polycrystalline (PC) and single crystal (SC) molybdenum mirrors were irradiated with 98Mo+, 1H+, 4He+, 11B+ and 184W+. Energies were chosen to impact the optically active region (up to 30 nm deep) of Mo mirrors. Some surfaces were coated by magnetron sputtering either with B or W films 4–65 nm thick. The overall objective was to simulate the neutron-induced damage and transmutation (H, He), and the impact of H, He, B, W on the optical performance of test mirrors, and on fuel retention. In parallel, a set of PC Mo mirrors irradiated with 1.6 MeV 98Mo3+ to a damage of 2 dpa and 20 dpa was installed in the JET tokamak for exposure during deuterium-tritium campaigns. Data from spectrophotometric, ion beam and microscopy techniques reveal: (i) the irradiation decreased specular reflectivity, whereby the differences between PC and SC in reflectivity are very small, (ii) He is retained in bubbles within 25–30 nm of the subsurface layer in all irradiated materials, (iii) W, either deposited or implanted, decreases reflectivity, but the strongest reflectivity degradation is caused by B deposition. Laboratory studies show the correlation of damage and H retention. Several cycles of W deposition and its removal from SC-Mo mirrors by plasma-assisted methods were also performed.
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| 2. |
- Kretschmer, Andreas, et al.
(författare)
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Analysis of (Al,Cr,Nb,Ta,Ti)-nitride and-oxynitride diffusion barriers in Cu-Si interconnects by 3D-Secondary Ion Mass Spectrometry
- 2023
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Ingår i: Materials Characterization. - : Elsevier. - 1044-5803 .- 1873-4189. ; 197
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Tidskriftsartikel (refereegranskat)abstract
- We report on the barrier performance of a nitride, and three oxynitrides of the system Al-Cr-Nb-Ta-Ti between Cu and Si. Different high-entropy sublattice nitrides have been tested before as diffusion barriers in this system, by depositing thin barriers on single crystalline Si substrates, followed by a thick Cu layer on top, and subsequent vacuum annealing. We investigated a reversed stacking sequence, by sputtering 15-30 nm of (Al,Cr,Nb,Ta,Ti)-O-N (between 0.5 and 63.7 at.% O) on polished polycrystalline Cu substrates, followed by 200 nm of Si. The samples were then vacuum annealed at 600, 700, 800 and 900 degrees C for 30 min. All four investigated coatings perform similar. Secondary Ion Mass Spectrometry depth profiling in high-current-bunched mode (lateral res-olution +/- 1 mu m) shows breakthrough of Si even at 600 degrees C. But 3D constructed images with Burst Alignment mode (lateral resolution of +/- 2 nm) reveal that this failure is a highly localized phenomenon, likely related to coarsening effects at the Cu grain boundaries, leading to punctuation of the diffusion barrier. Aside from this penetration, the majority of the area of each barrier coating retains its function. This in-depth analysis shows that the barrier function of the nitride and oxynitride coatings mostly stays intact up to 800 degrees C and fails completely at 900 degrees C.
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| 3. |
- Pitthan, Eduardo, et al.
(författare)
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In-situ, real-time investigation of the formation of oxygen-containing rare-earth hydrides by combining a quartz crystal microbalance and ion beam analysis
- 2023
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Ingår i: Materialia. - : Elsevier. - 2589-1529. ; 27
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Tidskriftsartikel (refereegranskat)abstract
- We present an in-situ and real-time investigation of the formation of YHO and GdHO thin films grown by reactive e(-)-beam evaporation. Mass changes were continuously monitored during deposition, oxidation, and illumination using a highly sensitive quartz crystal microbalance, while changes in chemical composition and depth profiles were investigated simultaneously by ion beam analysis. Results highlight the strong reactivity of freshly deposited YHx and GdHx films, even under ultra-high vacuum conditions. Oxidation starts at the surfaces of the films and the oxidation rate is strongly dependent on the O-2 pressure. The response of the system under ion beam irradiation and in-situ illumination is also presented and discussed. For the measured mass changes, a quantitative agreement better than 2% was observed between both techniques and demonstrates the consistency and sensitivity of this approach.
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| 4. |
- Pitthan, Eduardo, et al.
(författare)
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Influence of thermal annealing and of the substrate on sputter-deposited thin films from EUROFER97 on tungsten
- 2023
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Ingår i: Nuclear Materials and Energy. - : Elsevier BV. - 2352-1791. ; 35
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Tidskriftsartikel (refereegranskat)abstract
- The modification of sputter-deposited films from EUROFER97 on tungsten during and after annealing were investigated in-situ and ex-situ. The annealing resulted in a densification of the film, formation of large grains, segregation of W at the surface, and the formation of Fe-W compounds at the interfacial region. Similar structural modifications were observed also for a film annealed on a MgO substrate, with an exception to the change in composition (no increase of W concentration). Results indicate that the substrate significantly affects thermally induced modifications of re-deposited EUROFER97.
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| 5. |
- Pitthan, Eduardo, et al.
(författare)
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Thin films sputter-deposited from EUROFER97 in argon and deuterium atmosphere : Material properties and deuterium retention
- 2023
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Ingår i: Nuclear Materials and Energy. - : Elsevier. - 2352-1791. ; 34
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Tidskriftsartikel (refereegranskat)abstract
- Sputter-deposited thin films (33–1160 nm) from EUROFER97 were obtained on different substrates (C, Si, W, MgO) in argon and a mix of argon and deuterium atmosphere. The composition, microstructure, and mechanical properties of the films were analyzed and compared to those of the bulk material. The films feature lower density (-10%), higher hardness (+79%), and smaller crystallites in comparison to the bulk. Despite such differences, the elemental atomic composition of the films and the bulk was very similar, as determined by ion beam analysis. Deposition in deuterium-containing atmosphere resulted in a low deuterium incorporation (0.28% of atomic content), indicating low retention of hydrogen-isotopes in the deposited material.
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| 6. |
- Shams-Latifi, Jila, et al.
(författare)
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Experimental electronic stopping cross-section of tungsten bulk and sputter-deposited thin films for slow protons, deuterons and helium ions
- 2023
-
Ingår i: Nuclear Materials and Energy. - : Elsevier BV. - 2352-1791. ; 36
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Tidskriftsartikel (refereegranskat)abstract
- The experimental electronic stopping cross-section of tungsten for low-energy protons, deuterons, and helium ions is deduced from backscattering experiments from thin films and bulk using time-of-flight low-energy ion scattering (ToF-LEIS). Two complementary experimental approaches showed consistent results in the energy ranges of 0.3-10 keV for protons, 0.33-10 keV for deuterons, and 0.7-10 keV for He+ ions. In relative mea-surements, a Au sample was used as the reference, while in absolute energy loss measurements, sputter-deposited thin films of tungsten on carbon substrates were employed. The experimental energy-converted spectra were compared to Monte-Carlo simulations in both approaches for quantitative analysis taking the influence of plural and multiple scattering into account. The results show proportionality to the ion velocity. We discuss the present datasets in comparison to semiempirical modelling and predictions from theory.
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| 7. |
- Wolf, Philipp M., et al.
(författare)
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An in situ ToF-LEIS characterization of the surface of Ti-based thin films under oxygen exposure and at elevated temperatures
- 2023
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Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 638
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Tidskriftsartikel (refereegranskat)abstract
- Ti-based coatings are utilized in a wide variety of applications, from biomedical implants to mechanical tools. Insight into initial stages of processes triggered by gas exposure and temperature change in the near-surface region of such coatings is essential for the understanding of their macroscopic behavior. We present an in situ time-of-flight low-energy ion scattering (ToF-LEIS) approach for the non-destructive and depth-resolved study of composition and morphology of the immediate surface region with sub-nm resolution. Ti-based coatings, with increasing compositional complexity, starting from in situ grown Ti, followed by ex situ grown Ti, TiN, and (Ti,Al) N, are studied concerning effects of exposure to oxygen and elevated temperatures. On the clean in situ deposited Ti surface, a 1.9 nm thick oxide layer is observed after exposure to 4000 Langmuir oxygen at room temperature. In contrast, for ex situ grown samples, an oxidic surface layer not removable by surface ion sputtering is found to limit effects of further oxygen exposure. TiN does not show significant changes when exposed to oxygen at 370 & DEG;C. For (Ti,Al)N, a nm-thick Al-rich surface layer is observed at annealing temperatures above 600 & DEG;C, both in ultra-high vacuum and in 1.0 x 10-3 Pa of oxygen.
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| 8. |
- Wolf, Philipp Mika, 1994-
(författare)
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Synthesis and In Situ ToF-LEIS Analysis of Ultrathin Silicides and Ti-based Films
- 2023
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Thin films and coatings play a significant role in today’s society, with applications in electronics, optics, mechanics, and biomedicine. Further advancement in the field of surface coatings requires a good understanding of the unique features of ultrathin films and surfaces, which can only be reached with analysis techniques capable of resolving composition and morphology on a sub-nm scale.Time-of-flight low-energy ion scattering (ToF-LEIS), is such a method, with the surplus of non-destructive analysis. This thesis is devoted to demonstrating the use of in situ ToF-LEIS in the study of ultrathin film synthesis and surface modification. To showcase the possibilities offered by ToF-LEIS, two studies are presented: (1) The study of the phase transition of ultrathin nickel silicides and (2) the study of Ti-based coatings exposed to oxygen at elevated temperatures.In the first study, the growth and the phase transition sequence of Ni on Si(100) are investigated for initial film thicknesses below 4 nm. A partially ordered film with composition equivalent to Ni2Si is found for room-temperature deposition. Further, an unprecedented direct phase transition from orthorhombic δ-Ni2Si to epitaxial NiSi2-x, skipping the NiSi phase present in thicker films, is observed at 290 °C. This direct phase transition is explained by an enhanced interfacial effect between the substrate and the silicide for ultrathin films.The second study contains the in situ investigation of effects of low amounts of oxygen and high temperature on four coatings, in situ grown Ti as well as ex situ grown Ti, TiN, and (Ti,Al)N. On the ex situ samples, a persistent surface oxide layer is found, not removable by ion sputtering, limiting the effects of further oxygen exposure compared to the in situ sample. The nitride samples show a high stability towards further oxidation even at elevated temperatures. Additionally, the formation of an Al-rich surface layer is observed on (Ti,Al)N above 750 °C.
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