| 1. |
- Etula, Jarkko, et al.
(författare)
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Carbon nanotube membranes for EUV photolithography-a versatile material platform
- 2023
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Ingår i: International Conference on Extreme Ultraviolet Lithography 2023. - 9781510667488
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Konferensbidrag (refereegranskat)abstract
- Next generation of high-NA extreme ultraviolet (EUV) photolithography introduces higher power levels and faster reticle accelerations, enabling breakthrough in scanner efficiency. This results in higher temperatures and mechanical stresses on the EUV pellicles. Here we demonstrate scalable carbon nanotube (CNT) membrane mass production from a floating catalyst chemical vapor deposition (FC-CVD) reactor, using a direct dry deposition method. This direct high volume fabrication method yields highly uniform CNT networks with high strength and purity, enabling exceedingly thin CNT pellicles with high transparency at EUV. This end-To-end manufacturing process, starting from reagent gases, enables control and reproducibility over the final nanomaterial product. Control over synthesis allows tailoring of the carbon nanotube diameter and wall count (SWCNT or FWCNT), as well as control over the CNT network morphology such as the density, bundle size, and orientation of CNTs. The combination of this direct fabrication method with the exceptional mechanical and thermal properties of CNTs creates a versatile membrane platform, which can be further modified with post process steps such as purification to remove metal impurities. To enable conformal and thin coatings on CNTs, wet and dry functionalization steps are demonstrated to match the surface chemistry of CNTs to the specific deposition chemistry used in atomic layer (ALD), chemical vapor (CVD), or physical vapor (PVD) deposition processes. Thicker and denser CNT membranes with appropriate coatings are also suitable for other roles, such as filtering debris from an EUV source, blocking DUV photons and electrons, and providing a gas seal for differential pressure.
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| 2. |
- Garmysheva, Tatiana, et al.
(författare)
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Luminescence of ODC(II) in quartz and cristobalite glasses
- 2022
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Ingår i: Journal of Non-Crystalline Solids. - : Elsevier BV. - 0022-3093. ; 575
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Tidskriftsartikel (refereegranskat)abstract
- The results of the optical spectroscopy of twofold coordinated silicon centers – ODC(II) in quartz and cristobalite glasses are presented. The luminescence and excitation spectra attributed to different local symmetry of ODC(II) were investigated under synchrotron excitation in the VUV region. The observed differences in the luminescence and excitation spectra of ODC(II) are caused by the environment and, therefore, short-range order in the samples.
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| 3. |
- Kaminska, Agata, et al.
(författare)
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Defect-related photoluminescence and photoluminescence excitation as a method to study the excitonic bandgap of AlN epitaxial layers : Experimental and ab initio analysis
- 2020
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 117:23
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Tidskriftsartikel (refereegranskat)abstract
- We report defect-related photoluminescence (PL) and its vacuum ultraviolet photoluminescence excitation (PLE) spectra of aluminum nitride layers with various layer thicknesses and dislocation densities grown on two different substrates: sapphire and silicon. The defect-related transitions have been distinguished and examined in the emission and excitation spectra investigated under synchrotron radiation. The broad PL bands of two defect levels in the AlN were detected at around 3 eV and 4 eV. In the PLE spectra of these bands, a sharp excitonic peak originating most probably from the A-exciton of AlN was clearly visible. Taking into account the exciton binding energy, the measurements allow determination of the bandgaps of the investigated AlN samples and their temperature dependencies. Next, they are compared with the literature data obtained by other experimental techniques for bulk AlN crystals and layers grown on different substrates. The obtained results revealed that the AlN bandgap depends on the substrate. The theoretical analysis using density functional theory calculations showed that the effect is induced by the tetragonal strain related to the lattice mismatch between the substrate and the AlN layer, which has a strong influence on the spectral positions of the intrinsic excitons, and consequently on the bandgap of AlN layers.
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| 4. |
- Kappelhoff, Jan, et al.
(författare)
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Spectroscopic studies on Pr3+ doped YPO4 and LuPO4 upon vacuum ultraviolet (VUV) and synchrotron radiation excitation
- 2022
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Ingår i: Chemical Physics. - : Elsevier BV. - 0301-0104. ; 562
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Tidskriftsartikel (refereegranskat)abstract
- This work concerns the spectroscopic properties of micro- and nanoscale LuPO4:Pr3+ and microscale YPO4:Pr3+ upon excitation by VUV synchrotron radiation at a wide range of energies (5–45 eV) and two different temperatures (7 and 300 K). Both Pr3+ doped host materials show more intense UV-C emission than other Pr3+ phosphors studied earlier at FinEstBeAMS beamline under the same measurement conditions. The various relaxation processes of 5d14f1 → 4f2 interconfigurational transitions of Pr3+ and the difference between both hosts are discussed in detail.
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| 5. |
- Khanin, Vasilii, et al.
(författare)
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Exciton interaction with Ce3+ and Ce4+ ions in (LuGd)3(Ga,Al)5O12 ceramics
- 2021
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Ingår i: Journal of Luminescence. - : Elsevier BV. - 0022-2313. ; 237
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Tidskriftsartikel (refereegranskat)abstract
- Scintillators based on Ce-doped garnets are regularly co-doped with Mg2+ or Ca2+ to form Ce ions in 4+ state and reduce undesired afterglow. However overly high Ce4+ concentration leads to poor light yield performance. In order to understand the reason for variation in luminescence efficiency of Ce3+- and Ce4+-doped garnets we investigate the differences in energy conversion processes in complex LuGd2Ga3Al2O12:Ce3+/Ce4+ ceramics by means of VUV synchrotron irradiation. At first we have established via transmission spectroscopy and X-ray absorption spectroscopy that LuGd2Ga3Al2O12:Ce, Mg sample contains cerium in the 4+ state only. Then we show with VUV spectroscopy efficient interaction of excitons with Gd3+ and Ce3+, and lack of exciton absorption edge in LuGd2Ga3Al2O12:Ce4+ excitation spectrum. Instead, Ce4+ exhibits charge-transfer absorption band in the range of exciton emission. We suggest that when Ce4+ concentration becomes too high, the exciton → Gd3+ → Ce3+ energy transfer path is hindered. It leads to high intensity of Gd3+ luminescence in Lu1Gd2Ga3Al2O12:Ce, Mg ceramics, but lowered Ce3+ X-ray excited luminescence. Fine balance between 3+ and 4+ Ce concentrations is necessary to achieve the best performance of garnet scintillators.
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| 6. |
- Khanin, Vasilii M., et al.
(författare)
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Influence of 3d Transition Metal Impurities on Garnet Scintillator Afterglow
- 2020
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Ingår i: Crystal Growth and Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 20:5, s. 3007-3017
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Tidskriftsartikel (refereegranskat)abstract
- Garnet scintillators often suffer from undesired afterglow, the origin of which is not always well-understood. A possible origin is contamination with transition metal (TM) ions. These impurities can act as traps giving rise to afterglow. Alternatively, they may show long-lived (microsecond) d-d emission. Here we present a systematic study on the role of 3d TM impurities in (Lu,Gd)3(GaAl)5O12 garnet scintillators. Scintillator disks intentionally doped with ppm levels of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, or Zn were studied to identify TM-related traps in thermoluminescence (TSL) glow curves and their role in afterglow. For Ti, V, and Cr additional TSL peaks were observed that gave rise to RT afterglow in the 10-2-103 s time range, depending on garnet composition. On the millisecond time scale long-lived red/near-infrared emission was observed from Mn and Fe impurities, explained by spin-forbidden d-d emission. We show that afterglow can be reduced by the use of ultrapure raw materials. Other solutions include bandgap engineering for the garnet host to modify trap depths and applying optical filters to block the spin-forbidden d-d emission. The present study provides an insightful overview of the role of 3d TM impurities on afterglow in Ce-doped scintillators and procedures to predict and reduce afterglow. These insights will aid the development of Ce-doped garnets with superior afterglow behavior.
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| 7. |
- Kozlova, Anna P., et al.
(författare)
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Luminescence and vacuum ultraviolet excitation spectroscopy of cerium doped Gd3Ga3Al2O12 single crystalline scintillators under synchrotron radiation excitations
- 2020
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Ingår i: Results in Physics. - : Elsevier BV. - 2211-3797. ; 16
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Tidskriftsartikel (refereegranskat)abstract
- Cerium doped Gd3Ga3Al2O12 (GGAG) single crystals as well as GGAG:Ce single crystals co-doped by divalent (Mg2+, Ca2+), trivalent (Sc3+) or tetravalent (Zr4+, Ti4+) ions have been studied by means of the excitation luminescence spectroscopy in vacuum ultraviolet spectral range. Synchrotron radiation from the undulator beam was utilized for the luminescence excitation in the energy range from 4.5 to 800 eV. The influence of the co-dopant ions on the excitonic transitions as well as on the intrinsic defects in GGAG was revealed examining the luminescence emission and excitation spectra of both Gd3+ and Ce3+ ions in all single crystals studied. Special attention was paid to the analysis of Ce3+ excitation spectra in VUV spectral range (4.5–45 eV) where multiplication of electronic excitation (MEE) processes occur. It was obtained that GGAG:Ce single crystals having different co-dopant ions reveal distinguished efficiency of MEE. The role of intrinsic defects in MEE processes in the co-doped GGAG:Ce single crystals was elucidated.
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| 8. |
- Pankratov, Vladimir, et al.
(författare)
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Progress in development of a new luminescence setup at the FinEstBeAMS beamline of the MAX IV laboratory
- 2019
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Ingår i: Radiation Measurements. - : Elsevier BV. - 1350-4487. ; 121, s. 91-98
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Tidskriftsartikel (refereegranskat)abstract
- FinEstBeAMS is a new materials science beamline at the 1.5 GeV storage ring of the MAX IV Laboratory in Lund, Sweden. It has been built based on grazing incidence monochromatization of synchrotron light, which allows to cover a remarkably wide excitation energy range from ultraviolet to soft x-rays (4.5–1450 eV). A new mobile luminescence spectroscopy end station has been commissioned with design benefitting from the advantages of a high flux elliptically polarizing undulator light source. We report on the design of the luminescence end station, its technical realization and performance achieved so far. Special attention is paid to the experimental challenges for luminescence spectroscopy under grazing incidence excitation conditions. The first luminescence results obtained demonstrate a reliable performance of the advanced setup at FinEstBeAMS.
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| 9. |
- Pankratova, Viktorija, et al.
(författare)
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Time-resolved luminescence and excitation spectroscopy of Co-doped Gd3Ga3Al2O12 scintillating crystals
- 2020
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- Cerium doped Gd3Ga3Al2O12 (GGAG) single crystals as well as GGAG:Ce single crystals co-doped by divalent (Mg2+, Ca2+) and tetravalent (Zr4+, Ti4+) ions have been studied by means of time-resolved luminescence as well as the excitation luminescence spectroscopy in vacuum ultraviolet (VUV) and soft X-ray (XUV) spectral range. Tunable laser excitation was applied for time-resolved experiments in order to obtain luminescence decay curves under excitations in Ce3+, Gd3+ and excitonic absorption bands. The influence of the co-dopant ions on the Ce3+ luminescence decay kinetics is elucidated. The fastest luminescence decay was observed for the Mg2+ co-doped crystals under any excitation below bandgap energy indicating the perturbation of the 5d states of Ce3+ by Mg2+ ions. Synchrotron radiation was utilized for the luminescence excitation in the energy range from 4.5 to 800 eV. Special attention was paid to the analysis of Ce3+ excitation spectra in VUV and XUV spectral range where multiplication of electronic excitation (MEE) processes occur. Our results demonstrated that GGAG:Ce single crystals co-doped by Mg2+ ions as well as the GGAG:Ce crystal annealed in vacuum reveal the most efficient excitation of Ce3+ emission in VUV-XUV excitation range. The role of intrinsic defects in MEE processes in the co-doped as well as in the annealed GGAG:Ce single crystals is discussed.
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| 10. |
- Pejchal, Jan, et al.
(författare)
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Untangling the controversy on Ce3+luminescence in LaAlO3crystals
- 2022
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Ingår i: Materials Advances. - : Royal Society of Chemistry (RSC). - 2633-5409. ; 3:8, s. 3500-3512
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Tidskriftsartikel (refereegranskat)abstract
- Aluminum perovskites represent an important group of promising scintillation materials with excellent proportionality and energy resolution, but due to difficulties in crystal growth not much attention has been paid to them. We studied a Ce-doped LaAlO3lanthanum-aluminum perovskite (LaAP) because of its easy crystal growth facilitated by the large La3+cations in the matrix. Moreover, recent observations of intense blue luminescence by some researchers show that the potential of this material could not be ruled out. On the other hand, some reports claim that Ce3+luminescence is completely absent in the LaAP matrix. Therefore, we have decided to study this material in much greater detail using an extended set of correlated experiments to explain the observed discrepancies and underlying phenomena. Crystal growth by the micro-pulling-down method is reported together with the luminescence and scintillation properties. We demonstrate the influence of inclusions of other aluminate phases created during the crystal growth on the luminescence processes. The existence of the phases was simultaneously confirmed by observations using a scanning electron microscope, cathodoluminescence, energy-dispersive X-ray analysis and electron paramagnetic resonance (EPR), which were correlated with photoluminescence and scintillation studies. The EPR evidenced the incorporation of Ce ions in different environments comprising the LaAP matrix and inclusions. Based on these results, the luminescence mechanism is proposed and discussed and the low scintillation efficiency of the Ce-doped LaAP is explained together with the discrepancies in the literature.
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