| 1. |
- Landälv, Ludvig, 1982-, et al.
(författare)
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Phase evolution of radio frequency magnetron sputtered Cr-rich (Cr,Zr)(2)O-3 coatings studied by in situ synchrotron X-ray diffraction during annealing in air or vacuum
- 2019
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Ingår i: Journal of Materials Research. - : CAMBRIDGE UNIV PRESS. - 0884-2914 .- 2044-5326. ; 34:22, s. 3735-3746
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Tidskriftsartikel (refereegranskat)abstract
- The phase evolution of reactive radio frequency (RF) magnetron sputtered Cr0.28Zr0.10O0.61 coatings has been studied by in situ synchrotron X-ray diffraction during annealing under air atmosphere and vacuum. The annealing in vacuum shows t-ZrO2 formation starting at similar to 750-800 degrees C, followed by decomposition of the alpha-Cr2O3 structure in conjunction with bcc-Cr formation, starting at similar to 950 degrees C. The resulting coating after annealing to 1140 degrees C is a mixture of t-ZrO2, m-ZrO2, and bcc-Cr. The air-annealed sample shows t-ZrO2 formation starting at similar to 750 degrees C. The resulting coating after annealing to 975 degrees C is a mixture of t-ZrO2 and alpha-Cr2O3 (with dissolved Zr). The microstructure coarsened slightly during annealing, but the mechanical properties are maintained, with no detectable bcc-Cr formation. A larger t-ZrO2 fraction compared with alpha-Cr2O3 is observed in the vacuum-annealed coating compared with the air-annealed coating at 975 degrees C. The results indicate that the studied pseudo-binary oxide is more stable in air atmosphere than in vacuum.
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| 2. |
- Broekhuijsen, Sjoerd, 1993-, et al.
(författare)
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Synthesis and characterization of 11B4C containing Ni/Ti multilayers using combined neutron and X-ray reflectometry
- 2023
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Ingår i: Optical Materials Express. - : Optica Publishing Group. - 2159-3930 .- 2159-3930. ; 13:4, s. 1140-1149
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Tidskriftsartikel (refereegranskat)abstract
- The performance of multilayers in optical components, such as those used in neutron scattering instruments, is crucially dependent on the achievable interface width. We have shown how the interface width of Ni/Ti multilayers can be improved using the incorporation of B4C to inhibit the formation of nanocrystals and limit interdiffusion and intermetallic reactions at the interfaces. A modulated ion-assistance scheme was used to prevent intermixing and roughness accumulation throughout the layer stack. In this work we investigate the incorporation of low-neutron-absorbing 11B4C for Ni/Ti neutron multilayers. Combined fitting of neutron reflectivity and X-ray reflectivity measurements shows an elimination of accumulated roughness for the 11B4C containing multilayers with a mean interface width of 4.5 Å, resulting in an increase in reflectivity at the first Bragg peak by a factor of 2.3 and 1.5 for neutron and X-ray measurements, respectively.
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| 3. |
- Chang, Jui-Che, et al.
(författare)
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Domain epitaxial growth of Ta3N5 film on c-plane sapphire substrate
- 2022
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Ingår i: Surface & Coatings Technology. - : Elsevier. - 0257-8972 .- 1879-3347. ; 443
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Tidskriftsartikel (refereegranskat)abstract
- Tritantalum pentanitride (Ta3N5) semiconductor is a promising material for photoelectrolysis of water with high efficiency. Ta3N5 is a metastable phase in the complex system of TaN binary compounds. Growing stabilized single-crystal Ta3N5 films is correspondingly challenging. Here, we demonstrate the growth of a nearly single-crystal Ta3N5 film with epitaxial domains on c-plane sapphire substrate, Al2O3(0001), by magnetron sputter epitaxy. Introduction of a small amount ~2% of O2 into the reactive sputtering gas mixed with N2 and Ar facilitates the formation of a Ta3N5 phase in the film dominated by metallic TaN. In addition, we indicate that a single-phase polycrystalline Ta3N5 film can be obtained with the assistance of a Ta2O5 seed layer. With controlling thickness of the seed layer smaller than 10 nm and annealing at 1000 °C, a crystalline β phase Ta2O5 was formed, which promotes the domain epitaxial growth of Ta3N5 films on Al2O3(0001). The mechanism behind the stabilization of the orthorhombic Ta3N5 structure resides in its stacking with the ultrathin seed layer of orthorhombic β-Ta2O5, which is energetically beneficial and reduces the lattice mismatch with the substrate.
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| 4. |
- Chang, Jui-Che, et al.
(författare)
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Orthorhombic Ta3-xN5-yOy thin films grown by unbalanced magnetron sputtering : The role of oxygen on structure, composition, and optical properties
- 2021
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Ingår i: Surface & Coatings Technology. - : Elsevier. - 0257-8972 .- 1879-3347. ; 406
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Tidskriftsartikel (refereegranskat)abstract
- Direct growth of orthorhombic Ta3N5-type Ta-O-N compound thin films, specifically Ta3-xN5-yOy, on Si and sapphire substrates with various atomic fractions is realized by unbalanced magnetron sputtering. Low-degree fiber-textural Ta3-xN5-yOy films were grown through reactive sputtering of Ta in a gas mixture of N-2, Ar, and O-2 with keeping a partial pressure ratio of 3:2:0.1 in a total working pressure range of 5-30 mTorr. With increasing total pressure from 5 to 30 mTorr, the atomic fraction of O in the as-grown Ta3-xN5-yOy films was found to increase from 0.02 to 0.15 while that of N and Ta decrease from 0.66 to 0.54 and 0.33 to 0.31, respectively, leading to a decrease in b lattice constant up to around 1.3%. Metallic TaNx phases were formed without oxygen. For a working pressure of 40 mTorr, an amorphous, O-rich Ta-N-O compound film with a high O fraction of similar to 0.48, was formed, mixed with non-stoichiometric TaON and Ta2O5. By analyzing the plasma discharge, the increasing O incorporation is associated with oxide formation on top of the Ta target due to a higher reactivity of Ta with O than with N. The increase of O incorporation in the films also leads to a optical bandgap widening from similar to 2.22 to similar to 2.96 eV, which is in agreement with the compositional and structural changes from a crystalline Ta3-xN5-yOy to an amorphous O-rich Ta-O-N compound.
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| 5. |
- Dorri, Samira, 1988-, et al.
(författare)
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Enhanced quality of single crystal CrBx/TiBy diboride superlattices by controlling boron stoichiometry during sputter deposition
- 2024
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Ingår i: Applied Surface Science. - : Elsevier. - 0169-4332 .- 1873-5584.
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Tidskriftsartikel (refereegranskat)abstract
- Single-crystal CrB2/TiB2 diboride superlattices with well-defined layers are promising candidates for neutron optics. However, excess B in sputter-deposited TiBy using a single TiB2 target deteriorates the structural quality of CrBx/TiBy (0001) superlattices. We study the influence of co-sputtering of TiB2 + Ti on the stoichiometry and crystalline quality of 300-nm-thick TiBy single layers and CrBx/TiBy (0001) superlattices on Al2O3(0001) substrates grown by DC magnetron sputter epitaxy at growth-temperatures TS ranging from 600 to 900 °C. By controlling the relative applied powers to the TiB2 and Ti magnetrons, y could be reduced from 3.3 to 0.9. TiB2.3 grown at 750 °C exhibited epitaxial domains about 10x larger than non-co-sputtered films. Close-to-stoichiometry CrB1.7/TiB2.3 superlattices with modulation periods Λ = 6 nm grown at 750 °C showed the highest single crystal quality and best layer definition. TiB2.3 layers display rough top interfaces indicating kinetically limited growth while CrB1.7 forms flat and abrupt top interfaces indicating epitaxial growth with high adatom mobility.
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| 6. |
- Eriksson, Fredrik, 1975-, et al.
(författare)
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Interface engineering of short-period Ni/V multilayer X-ray mirrors
- 2006
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 500:1-2, s. 84-95
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Tidskriftsartikel (refereegranskat)abstract
- Low-energy ion-assisted magnetron sputter deposition has been used for the synthesis of highly reflective Ni/V multilayer soft X-ray mirrors. A low ion energy and a high ion-to-metal flux ratio were employed in order to stimulate the adatom mobility while minimizing ion-induced intermixing at the interfaces. An analytic model, based on the binary collision approximation, was used in order to gain insight into low-energy ion-surface interactions as a function of ion energy and ion-to-metal flux ratio. The model predicted a favorable region in the ion energy-flux parameter space where only surface atomic displacements are stimulated during growth of Ni and V for multilayers. For a series of Ni/V multilayer mirrors with multilayer periods about Λ = 1.2 nm, grown with a continuous ion assistance using energies in the range 7-36 eV and with ion-to-metal flux ratios ΦNi = 4.7 and ΦV=20.9, specular and diffuse X-ray scattering analyses revealed that ion energies of ∼27-31 eV produced the best trade-off between reduced interfacial roughness and intermixing. However, it was also concluded that an interface mixing of about ± 1 atomic distance is unavoidable when a continuous flux of assisting ions is used. To overcome this limitation, a sophisticated interface engineering technique was employed, where the first 0.3 nm of each layer was grown with a high-flux low-energy ion assistance and the remaining part was grown with a slightly higher ion energy. This method was demonstrated to largely eliminate the intermixing while maintaining the smoothening effect of ion assistance. Two Ni/V multilayer soft X-ray mirror structures, one with 500 periods designed for near-normal incidence and one 150 periods reflecting polarizer at the Brewster angle, were grown utilizing the interface engineering concept. Both the near-normal incidence reflectivity as well as polarizability were improved by a factor of 2 as compared to previously reported data for an X-ray energy of E = 511 eV. © 2005 Elsevier B.V. All rights reserved.
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| 7. |
- Eriksson, Fredrik, 1975-, et al.
(författare)
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Morphology control in Ni/Ti multilayer neutron mirrors by ion-assisted interface engineering and B4C incorporation
- 2023
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Ingår i: Optical Materials Express. - : Optica Publishing Group. - 2159-3930 .- 2159-3930. ; 13:5, s. 1424-1439
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Tidskriftsartikel (refereegranskat)abstract
- The optical contrast and minimum layer thickness of Ni/Ti broadband neutron multilayer supermirrors is usually hampered by an interface width, typically 0.7 nm, caused by nanocrystallites, interdiffusion, and/or intermixing. We explore the elimination of nanocrystallites in combination with interface smoothening by modulation of ion assistance during magnetron sputter deposition of 0.8 to 6.4 nm thick Ni and Ti layers. The amorphization is achieved through incorporation of natural B4C where B and C preferably bond to Ti. A two-stage substrate bias was applied to each layer; -30 V for the initial 1 nm followed by -100 V for the remaining part, generating multilayer mirrors with interface widths of 0.40-0.45 nm. The results predict that high performance supermirrors with m-values as high as 10 are feasible by using 11B isotope-enriched B4C combined with temporal control of the ion assistance.
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| 8. |
- Ghafoor, Naureen, 1975-, et al.
(författare)
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Impact of B4C co-sputtering on structure and optical performance of Cr/Sc multilayer X-ray mirrors
- 2017
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Ingår i: Optics Express. - : Optical Society of America. - 1094-4087. ; 25:15, s. 18274-18287
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Tidskriftsartikel (refereegranskat)abstract
- The influence of B4C incorporation during magnetron sputter deposition of Cr/Sc multilayers intended for soft X-ray reflective optics is investigated. Chemical analysis suggests formation of metal: boride and carbide bonds which stabilize an amorphous layer structure, resulting in smoother interfaces and an increased reflectivity. A near-normal incidence reflectivity of 11.7%, corresponding to a 67% increase, is achieved at λ = 3.11 nm upon adding 23 at.% (B + C). The advantage is significant for the multilayer periods larger than 1.8 nm, where amorphization results in smaller interface widths, for example, giving 36% reflectance and 99.89% degree of polarization near Brewster angle for a multilayer polarizer. The modulated ion-energy-assistance during the growth is considered vital to avoid intermixing during the interface formation even when B + C are added.
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| 9. |
- Zubayer, Anton, 1995-
(författare)
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Enhanced Polarizing Neutron Optics with 11B4C Incorporation : SLD Tunability, Interface Refinement, and Elimination of Magnetic Coercivity
- 2023
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis explores novel strategies for improving Fe-based polarizing neutron optics, a critical part for improving neutron scattering methods to study materials science, physics, biology, medicine, chemistry and cultural heritage. Polarization analysis is important in uncovering data on magnetic domains, protein structures, molecular composition and orientation in biological systems, and ion-diffusion mechanisms that would otherwise be inaccessible. However, conventional methods, particularly state-of-the-art multilayer polarizing neutron optics, are hindered by low specular reflectivity, low polarization at higher scattering vectors/angles, high diffuse scattering and the need for high external magnetic fields for polarizer magnetization. The outcomes leading to this thesis, introduces the concept of scattering length density tuning, strategies to decrease the interface width, the diminishing of lateral correlation and magnetic coercivity. All improvements realized by introducing 11B4C in clever ways.The multilayers were deposited using ion-assisted DC magnetron sputter deposition (DCMS). Our improvement of Fe-based multilayer mirrors all revolves around the use of 11B4C. 11B4C in various concentrations can be used together with other materials to tune the scattering length density contrasts. It can amorphize the interfaces and layers to achieve smaller interface width, diminish lateral correlations and eliminate magnetic coercivity. In other words, increase reflectivity, increase polarization, decrease diffuse scattering and saturate at lower fields. The multilayers were mainly characterized using X-ray reflectivity (XRR), X-ray diffraction (XRD), grazing incidence small/wide angle X-ray scattering (GISAXS/GIWAXS), elastic recoil detection analysis (ERDA), magneto-optical Kerr effect (MOKE), vibrating sample magnetometry (VSM), transmission electron microscopy (TEM) and polarized neutron reflectivity (PNR). All results prove the benefit of using 11B4C in Fe-based polarizing neutron optics.
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| 10. |
- Ahrentorp, Fredrik, et al.
(författare)
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Sensitive magnetic biodetection using magnetic multi-core nanoparticles and RCA coils
- 2017
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Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853 .- 1873-4766. ; 427, s. 14-18
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Tidskriftsartikel (refereegranskat)abstract
- We use functionalized iron oxide magnetic multi-core particles of 100 nm in size (hydrodynamic particle diameter) and AC susceptometry (ACS) methods to measure the binding reactions between the magnetic nanoparticles (MNPs) and bio-analyte products produced from DNA segments using the rolling circle amplification (RCA) method. We use sensitive induction detection techniques in order to measure the ACS response. The DNA is amplified via RCA to generate RCA coils with a specific size that is dependent on the amplification time. After about 75 min of amplification we obtain an average RCA coil diameter of about 1 mu m. We determine a theoretical limit of detection (LOD) in the range of 11 attomole (corresponding to an analyte concentration of 55 fM for a sample volume of 200 mu L) from the ACS dynamic response after the MNPs have bound to the RCA coils and the measured ACS readout noise. We also discuss further possible improvements of the LOD.
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