| 1. |
- Zhou, Yushan, et al.
(författare)
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Micro ion beam analysis for the erosion of beryllium marker tiles in a tokamak limiter
- 2019
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - : Elsevier BV. - 0168-583X .- 1872-9584. ; 450, s. 200-204
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Tidskriftsartikel (refereegranskat)abstract
- Beryllium limiter marker tiles were exposed to plasma in the Joint European Torus to diagnose the erosion of main chamber wall materials. A limiter marker tile consists of a beryllium coating layer (7-9 mu m) on the top of bulk beryllium, with a nickel interlayer (2-3 mu m) between them. The thickness variation of the beryllium coating layer, after exposure to plasma, could indicate the erosion measured by ion beam analysis with backscattering spectrometry. However, interpretations from broad beam backscattering spectra were limited by the non-uniform surface structures. Therefore, micro-ion beam analysis (mu-IBA) with 3 MeV proton beam for Elastic back scattering spectrometry (EBS) and PIXE was used to scan samples. The spot size was in the range of 3-10 mu m. Scanned areas were analysed with scanning electron microscopy (SEM) as well. Combining results from mu-IBA and SEM, we obtained local spectra from carefully chosen areas on which the surface structures were relatively uniform. Local spectra suggested that the scanned area (approximate to 600 mu m x 1200 mu m) contained regions with serious erosion with only 2-3 mu m coating beryllium left, regions with intact marker tile, and droplets with 90% beryllium. The nonuniform erosion, droplets mainly formed by beryllium, and the possible mixture of beryllium and nickel were the major reasons that confused interpretation from broad beam EBS.
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| 2. |
- Dalbauer, V, et al.
(författare)
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On the phase formation of cathodic arc evaporated Al1-xCrx-based intermetallic coatings and substoichiometric oxides
- 2018
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Ingår i: Surface & Coatings Technology. - : ELSEVIER SCIENCE SA. - 0257-8972 .- 1879-3347. ; 352, s. 392-398
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Tidskriftsartikel (refereegranskat)abstract
- The phase evolution of Al1-xCrx-based intermetallic coatings and corresponding substoichiometric oxides grown by cathodic arc evaporation was investigated in order to obtain a better understanding of the relation between oxygen flow rate, Al and Cr content, and structural evolution of the coatings deposited. When using 20 sccm Ar, or 50 sccm O-2, or 100 sccm O-2 per active source (p.a.s.) the cathode reaction zone consists of various intermetallic Al-Cr-compounds, which are in good agreement with the binary Al-Cr phase diagram. This is generally also reflected in the phase composition of the metallic and substoichiometric oxide coatings. The Al-rich compositions, Al0.75Cr0.25 and Al0.70Cr0.30, show a strong tendency for the formation of gamma(1)-Al8Cr5 phases. Mostly, the coating compositions of the metallic constituents of the synthesised intermetallic and substoichiometric oxide coatings deviate from the elemental compositions of the cathode, show enrichment in Cr. This deviation is more pronounced for Cr-rich cathodes using low O-2 flow rates during deposition. The dense columnar structure of the intermetallic coatings (hardness values between 2.5 and 10.2 GPa) turns into a nano-composite-like morphology for depositions with 50 and 100 sccm O-2 p.a.s., which in turn leads to a significant hardness increase up to similar to 24 GPa. Among all coatings investigated, the Cr-rich compositions have higher hardness and denser morphology than the Al-rich layers.
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| 3. |
- Englund, Sven, et al.
(författare)
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Characterization of TiN back contact interlayers with varied thickness for Cu2ZnSn(S,Se)4 thin film solar cells
- 2017
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 639, s. 91-97
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Tidskriftsartikel (refereegranskat)abstract
- TiN thin films have previously been used as intermediate barrier layers on Mo back contacts in CZTS(e) solar cells to suppress excessive reaction of the Mo in the annealing step. In this work, TiN films with various thickness (20, 50 and 200 nm) were prepared with reactive DC magnetron sputtering on Mo/SLG substrates and annealed, without CZTS(e) layers, in either S or Se atmospheres. The as-deposited references and the annealed samples were characterized with X-ray Photoelectron Spectroscopy, X-ray Diffraction, Time-of-Flight-Elastic Recoil Detection Analysis, Time-of-Flight-Medium-Energy Ion Scattering, Scanning Electron Microscopy and Scanning Transmission Electron Microscopy – Electron Energy Loss Spectroscopy. It was found that the as-deposited TiN layers below 50 nm show discontinuities, which could be related to the surface roughness of the Mo. Upon annealing, TiN layers dramatically reduced the formation of MoS(e)2, but did not prevent the sulfurization or selenization of Mo. The MoS(e)2 had formed near the discontinuities, both below and above the TiN layers. Another unexpected finding was that the thicker TiN layer increased the amount of Na diffused to the surface after anneal, and we suggest that this effect is related to the Na affinity of the TiN layers and the MoS(e)2 thickness.
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| 4. |
- Englund, Sven, et al.
(författare)
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TiN Interlayers with Varied Thickness in Cu2ZnSnS(e)(4) Thin Film Solar Cells : Effect on Na Diffusion, Back Contact Stability, and Performance
- 2018
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Ingår i: Physica Status Solidi (a) applications and materials science. - : Wiley. - 1862-6300 .- 1862-6319. ; 215:23
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Tidskriftsartikel (refereegranskat)abstract
- In this study, interlayers with varied thickness of TiN between Cu2ZnSnS(e)(4) (CZTS(e)) absorbers and Mo on soda-lime glass substrates are investigated for CZTS(e) thin film solar cells. Na diffusion is analyzed using Secondary Ion Mass Spectrometry and it is found that the use of thick TiN interlayers facilitates Na diffusion into the absorbers. The CZTS(e)/TiN/Mo interfaces are scrutinized using Transmission Electron Microscopy (TEM) Electron Energy Loss Spectroscopy (EELS). It is found that diffusion of chalcogens present in the precursor occurs through openings, resulting from surface roughness in the Mo, in the otherwise chemically stable TiN interlayers, forming point contacts of MoS(e)(2). It is further established that both chalcogens and Mo diffuse along the TiN interlayer grain boundaries. Solar cell performance for sulfur-annealed samples improved with increased thickness of TiN, and with a 200 nm TiN interlayer, the solar cell performance is comparable to a typical Mo reference. Pure TiN bulk contacts are investigated and shown to work, but the performance is still inferior to the TiN interlayer back contacts. The use of thick TiN interlayers offers a pathway to achieve high efficiency CZTS(e) solar cells on highly inert back contacts.
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| 5. |
- Fluch, Ulrike, et al.
(författare)
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Uniform distribution of post-synthetic linker exchange in metal-organic frameworks revealed by Rutherford backscattering spectrometry
- 2017
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Ingår i: Chemical Communications. - : ROYAL SOC CHEMISTRY. - 1359-7345 .- 1364-548X. ; 53:48, s. 6516-6519
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Tidskriftsartikel (refereegranskat)abstract
- Rutherford backscattering spectrometry (RBS) has been used for the first time to study post-synthetic linker exchange (PSE) in metal-organic frameworks. RBS is a non-invasive method to quantify the amount of introduced linker, as well as providing a means for depth profiling in order to identify the preferred localization of the introduced linker. The exchange of benzenedicarboxylate (bdc) by similarly sized 2-iodobenzenedicarboxylate (I-bdc) proceeds considerably slower than migration of I-dbc through the UiO-66 crystal. Consequently, the I-bdc is found evenly distributed throughout the UiO-66 samples, even at very short PSE exposure times.
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| 6. |
- Glechner, T., et al.
(författare)
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Tuning structure and mechanical properties of Ta-C coatings by N-alloying and vacancy population
- 2018
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Tailoring mechanical properties of transition metal carbides by substituting carbon with nitrogen atoms is a highly interesting approach, as thereby the bonding state changes towards a more metallic like character and thus ductility can be increased. Based on ab initio calculations we could prove experimentally, that up to a nitrogen content of about 68% on the non-metallic sublattice, Ta-C-N crystals prevail a face centered cubic structure for sputter deposited thin films. The cubic structure is partly stabilized by non-metallic as well as Ta vacancies-the latter are decisive for nitrogen rich compositions. With increasing nitrogen content, the originally super-hard fcc-TaC0.71 thin films soften from 40 GPa to 26 GPa for TaC0.33N0.67, accompanied by a decrease of the indentation modulus. With increasing nitrogen on the non-metallic sublattice (hence, decreasing C) the damage tolerance of Ta-C based coatings increases, when characterized after the Pugh and Pettifor criteria. Consequently, varying the non-metallic sublattice population allows for an effective tuning and designing of intrinsic coating properties.
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| 7. |
- Kalamara, A., et al.
(författare)
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Determination of the Ir-193(n, 2n) reaction cross section and correction methodology for the Ir-191(n, gamma) contamination
- 2019
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Ingår i: European Physical Journal A. - : SPRINGER. - 1434-6001 .- 1434-601X. ; 55:10
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Tidskriftsartikel (refereegranskat)abstract
- The cross section of the Ir-193(n, 2n)Ir-192 reaction has been determined by means of the activation technique, relative to the Al-27(n, alpha) and Au-197(n, 2n) reference reactions cross sections, at neutron beam energies ranging from 10 to 21 MeV. The quasi-monoenergetic neutron beams were produced at the 5.5 MV Tandem T11/25 Accelerator Laboratory of NCSR "Demokritos" via the H-2(d, n) and H-3(d, n) reactions. The induced gamma-ray activity of the irradiated target and reference foils was measured with high resolution HPGe detectors. In order to correct for the contribution of the Ir-191(n, gamma)Ir-192 reaction, which is open to low energy parasitic neutrons, a recently developed analysis method was implemented and it is presented in great detail. Furthermore, cross section theoretical calculations were carried out using the EMPIRE and TALYS codes over a wide energy range.
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| 8. |
- Kantre, Karim-Alexandros, et al.
(författare)
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Assessing electronic energy loss of heavy ions detected in reflection geometry
- 2021
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Ingår i: Surface and Interface Analysis. - : John Wiley & Sons. - 0142-2421 .- 1096-9918. ; 53:7, s. 650-657
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Tidskriftsartikel (refereegranskat)abstract
- We study energy loss spectra of bromine ions scattered from silver thin films in the range of 4 to 36 MeV in forward reflection geometry. The different contributions to the energy loss were analyzed by complementary Monte-Carlo simulations. We assess the dependence of the scattering yield as well as nuclear and electronic losses on the penetration depth of detected ions. To investigate the entanglement of energy loss and depth information, electronic stopping cross sections were deduced from the experimental spectra by two different approaches: a) assuming a single scattering model and b) making use of Monte-Carlo simulations. The data obtained from the two approaches are compared and we assess the relative contributions from nuclear stopping as well as from the effect of multiple scattering on trajectory length. Results of both methods are compared to data from literature, to SRIM predictions and discussed in the context of composition depth‑profiling.
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| 9. |
- Kantre, Karim-Alexandros, et al.
(författare)
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Investigation of the energy loss of I in Au at energies below the Bragg peak
- 2019
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - : Elsevier BV. - 0168-583X .- 1872-9584. ; 450, s. 37-42
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Tidskriftsartikel (refereegranskat)abstract
- The energy loss of iodine in gold was investigated at energies below the Bragg peak. With the present work, the range of the available experimental data is extended to significantly lower energies, while the nuclear stopping power contribution is taken into account. Experiments were performed on thin film targets in reflection geometry. Electronic stopping cross sections were extracted by different approaches from experimental spectra. The obtained results have been compared to tabulated values from SRIM and previously published experimental data, where available. For all energies the obtained values are consistently higher than predicted by SRIM. Monte Carlo simulations (TRIM) have been performed to study path length distributions and the influence of nuclear stopping on the total energy loss. The results from the calculations indicate that the experimental geometry might be an important factor affecting the observed energy loss due to a selection of specific trajectories.
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| 10. |
- Kirnbauer, A., et al.
(författare)
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Mechanical properties and thermal stability of reactively sputtered multi-principal-metal Hf-Ta-Ti-V-Zr nitrides
- 2020
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Ingår i: Surface & Coatings Technology. - : ELSEVIER SCIENCE SA. - 0257-8972 .- 1879-3347. ; 389
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Tidskriftsartikel (refereegranskat)abstract
- Crystalline (Hf,Ta,Ti,V,Zr)N nitride thin films, with a high-entropy metal-sublattice, were synthesized at 440 degrees C by reactive magnetron sputtering using an equimolar Hf-Ta-Ti-V-Zr-compound target. The coatings are single-phase fcc structured mono-nitrides for N-2/(Ar + N-2) flow-rate-ratios (f(N2)) between 30 and 45%. For higher f(N2) a small fraction of a second phase (next to the fcc matrix) can be detected by X-ray diffraction (XRD) and selected area electron diffraction (SAED). All coatings studied (prepared with f(N2) between 30 and 60%) show similar chemical compositions and hardness (H) values between 30.0 and 34.0 GPa with indentation moduli of similar to 460 GPa. Atom probe tomography (APT) indicates a homogenous distribution of all elements within our fcc-(Hf,Ta,Ti,V,Zr)N even after vacuum-annealing at 1300 degrees C. While H decreased from 32.5 to 28.1 GPa by this annealing treatment, the coating is still single-phase fcc structured with a defect density (expressed by XRD and SAED features, transmission electron microscopy contrast, and grain sizes) comparable to the as-deposited state. Only after vacuum-annealing at 1500 degrees C, XRD and APT reveal the formation of hexagonal structured (Ta,V)(2)N. The onset of nitrogen-loss - detected by thermogravimetric analysis - is similar to 1350 degrees C. Based on our results we can conclude that the sluggish diffusion within our fcc-(Hf,Ta,Ti,V,Zr)N warrants the single-phase fcc structure up to 1300 degrees C, although ab initio based calculations would suggest the lower-entropy products [fcc-(Hf,Zr)N, fcc-(Ta,V)N, and fcc-TiN] and [fcc-(Hf,Zr)N and fcc-(Ta,Ti,V)N] to be energetically more stable up to 1302 K.
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