| 1. |
- Chayanun, Lert, et al.
(author)
-
Combining Nanofocused X-Rays with Electrical Measurements at the NanoMAX Beamline
- 2019
-
In: Crystals. - : MDPI AG. - 2073-4352. ; 9:8
-
Journal article (peer-reviewed)abstract
- The advent of nanofocused X-ray beams has allowed the study of single nanocrystals and complete nanoscale devices in a nondestructive manner, using techniques such as scanning transmission X-ray microscopy (STXM), X-ray fluorescence (XRF) and X-ray diffraction (XRD). Further insight into semiconductor devices can be achieved by combining these techniques with simultaneous electrical measurements. Here, we present a system for electrical biasing and current measurement of single nanostructure devices, which has been developed for the NanoMAX beamline at the fourth-generation synchrotron, MAX IV, Sweden. The system was tested on single InP nanowire devices. The mechanical stability was sufficient to collect scanning XRD and XRF maps with a 50 nm diameter focus. The dark noise of the current measurement system was about 3 fA, which allowed fly scan measurements of X-ray beam induced current (XBIC) in single nanowire devices.
|
|
| 2. |
- Dierks, Hanna, et al.
(author)
-
3D X-ray microscopy with a CsPbBr3 nanowire scintillator
- 2023
-
In: Nano Research. - : Springer Science and Business Media LLC. - 1998-0124 .- 1998-0000. ; 16:1, s. 1084-1089
-
Journal article (peer-reviewed)abstract
- X-ray microscopy is an essential imaging method in many scientific fields, which can be extended to three-dimensional (3D) using tomography. Recently, metal halide perovskite (MHP) nanomaterials have become a promising candidate for X-ray scintillators, due to their high light yield, high spatial resolution, and easy fabrication. Tomography requires many projections and therefore scintillators with excellent stability. This is challenging for MHPs, which often suffer from fast degradation under X-ray irradiation and ambient conditions. Here, we demonstrate that MHP scintillators of CsPbBr3 nanowires (diameter: 60 nm, length: 5–9 µm) grown in anodized aluminum oxide (CsPbBr3 NW/AAO) have sufficient stability for X-ray micro-tomography. A tomogram was taken with a Cu X-ray source over 41 h (dose 4.2 Gyair). During this period the scintillator brightness fluctuated less than 5%, which enabled a successful reconstruction. A long-term study with 2 weeks of continuous X-ray exposure (37.5 Gyair) showed less than 14% fluctuations in brightness and no long-term degradation, despite variations in the ambient relative humidity from 7.4 %RH to 34.2 %RH. The resolution was stable at (180 ± 20) 1pmm−1, i.e., about 2.8 micron. This demonstrates that CsPbBr3 NW/AAO scintillators are promising candidates for high resolution X-ray imaging detectors.
|
|
| 3. |
- Dierks, Hanna, et al.
(author)
-
A versatile laboratory setup for high resolution X-ray phase contrast tomography and scintillator characterization
- 2023
-
In: Journal of X-Ray Science and Technology. - 0895-3996. ; 31:1, s. 1-12
-
Journal article (peer-reviewed)abstract
- BACKGROUND: X-ray micro-tomography (μCT) is a powerful non-destructive 3D imaging method applied in many scientific fields. In combination with propagation-based phase-contrast, the method is suitable for samples with low absorption contrast. Phase contrast tomography has become available in the lab with the ongoing development of micro-focused tube sources, but it requires sensitive and high-resolution X-ray detectors. The development of novel scintillation detectors, particularly for microscopy, requires more flexibility than available in commercial tomography systems. OBJECTIVE: We aim to develop a compact, flexible, and versatile μCT laboratory setup that combines absorption and phase contrast imaging as well as the option to use it for scintillator characterization. Here, we present details on the design and implementation of the setup. METHODS: We used the setup for μCT in absorption and propagation-based phase-contrast mode, as well as to study a perovskite scintillator. RESULTS: We show the 2D and 3D performance in absorption and phase contrast mode, as well as how the setup can be used for testing new scintillator materials in a realistic imaging environment. A spatial resolution of around 1.3μm is measured in 2D and 3D. CONCLUSIONS: The setup meets the needs for common absorption μCT applications and offers increased contrast in phase contrast mode. The availability of a versatile laboratory μCT setup allows not only for easy access to tomographic measurements, but also enables a prompt monitoring and feedback beneficial for advances in scintillator fabrication.
|
|
| 4. |
- Dierks, Hanna, et al.
(author)
-
Experimental optimization of X-ray propagation-based phase contrast imaging geometry
- 2020
-
In: Optics Express. - 1094-4087. ; 28:20, s. 29562-29575
-
Journal article (peer-reviewed)abstract
- Propagation-based phase contrast imaging (PB-PCI) with an X-ray lab source is a powerful technique to study low absorption samples, e.g. soft tissue or plastics, on the micrometer scale but is often limited by the low flux and coherence of the source. The setup geometry is essential for the performance since there is a trade-off where a short source distance yields a high contrast-to-noise ratio (CNR) but a low relative fringe contrast. While theoretical optimization strategies based on Fresnel propagation have been reported, there is a need for experimental testing of these models. Here, we systematically investigate this trade-off experimentally using two different setups with high-resolution detectors: a custom-built system with a Cu X-ray source and a commercial system (Zeiss Xradia) with a W source. The fringe contrast, CNR and fringe separation for a low-absorption test sample were measured for 130 different combinations of magnification and overall distances. We find that these figures-of-merit are sensitive to the magnification and that an optimum can be found that is independent of the overall source-detector distance. In general, we find that the theoretical models show excellent agreement with the measurements. However, this requires the complicated X-ray spectrum to be considered, in particular for the broadband W source.
|
|
| 5. |
- Dierks, Hanna, et al.
(author)
-
Optimization of phase contrast imaging with a nano-focus x-ray tube
- 2023
-
In: Applied Optics. - 1559-128X. ; 62:20, s. 5502-5507
-
Journal article (peer-reviewed)abstract
- Propagation-based phase contrast imaging with a laboratory x-ray source is a valuable tool for studying samples that show only low absorption contrast, either because of low density, elemental composition, or small feature size. If a propagation distance between sample and detector is introduced and the illumination is sufficiently coherent, the phase shift in the sample will cause additional contrast around interfaces, known as edge enhancement fringes. The strength of this effect depends not only on sample parameters and energy but also on the experimental geometry, which can be optimized accordingly. Recently, x-ray lab sources using transmission targets have become available, which provide very small source sizes in the few hundred nanometer range. This allows the use of a high-magnification geometry with a very short source-sample distance, while still achieving sufficient spatial coherence at the sample position. Moreover, the high geometrical magnification makes it possible to use detectors with a larger pixel size without reducing the image resolution. Here, we explore the influence of magnification on the edge enhancement fringes in such a geometry. We find experimentally and theoretically that the fringes become maximal at a magnification that is independent of the total source-detector distance. This optimal magnification only depends on the source size, the steepness of the sample feature, and the detector resolution. A stronger influence of the sample feature on the optimal magnification compared to low-magnification geometries is observed.
|
|
| 6. |
- Dierks, Hanna
(author)
-
X-ray Phase Contrast Tomography : Setup and Scintillator Development
- 2023
-
Doctoral thesis (other academic/artistic)abstract
- X-ray microscopy and micro-tomography (μCT) are valuable non-destructive examination methods in many disciplines such as bio-medical research, archaeometry, material science and paleontology. Besides being implemented at synchrotrons radiation sources, laboratory setups using an X-ray tube and high-resolution scintillation detector routinely provide information on the micrometre scale. To improve the image contrast for small and low-density samples, it is possible to introduce a propagation distance between sample and detector to perform propagation-based phase contrast imaging (PB-PCI). This contrast mode relies on a sufficiently coherent illumination and is characterised by the appearance of an additional intensity modulations (‘edge enhancement fringes’) around interfaces in the image. The strength of this effect depends on hardware as well as geometry parameters. This thesis describes the development of a laboratory setup for X-ray μCT with a PB-PCI option. It contains the theoretical and technical background of the setup design as well the characterization of the achieved performance.Moreover, the optimization of the PB-PCI geometry was explored both theoretically as well as experimentally for three different setups. A simple rule for finding the optimal magnification to achieve high phase contrast for edge features was deduced. The effect of the polychromatic source spectrum und detector sensitivity was identified and included into the theoretical model.Besides application and methodological studies, the setup was used to test and characterise new X-ray scintillator materials. Recently, metal halide perovskite nanocrystals (MHP NCs) have gained attention due to their outstanding opto-electronic performance. The main challenge for their use and commercialization is their low long-term stability against humidity, temperature, and light exposure. Here, a CsPbBr3 scintillator comprised of an ordered array of nanowires (NW) in an anodized aluminium oxide (AAO) membrane is presented as a promising new scintillator for X-ray microscopy and μCT. It shows a high light yield under X-ray exposure which improves with smaller NW diameter and higher NW length. In contrast to many other MHP materials this scintillator shows good stability under continuous X-ray exposure and changing environmental conditions over extended time spans of several weeks. This makes it suitable for tomography, which is demonstrated by acquiring the first high-resolution tomogram using a MHP scintillator with the presented laboratory setup.
|
|
| 7. |
- Kalbfleisch, Sebastian, et al.
(author)
-
X-ray in-line holography and holotomography at the NanoMAX beamline
- 2022
-
In: Journal of Synchrotron Radiation. - : International Union of Crystallography (IUCr). - 0909-0495 .- 1600-5775. ; 29, s. 224-229
-
Journal article (peer-reviewed)abstract
- Coherent X-ray imaging techniques, such as in-line holography, exploit the high brilliance provided by diffraction-limited storage rings to perform imaging sensitive to the electron density through contrast due to the phase shift, rather than conventional attenuation contrast. Thus, coherent X-ray imaging techniques enable high-sensitivity and low-dose imaging, especially for low-atomic-number (Z) chemical elements and materials with similar attenuation contrast. Here, the first implementation of in-line holography at the NanoMAX beamline is presented, which benefits from the exceptional focusing capabilities and the high brilliance provided by MAX IV, the first operational diffractionlimited storage ring up to approximately 300 eV. It is demonstrated that in-line holography at NanoMAX can provide 2D diffraction-limited images, where the achievable resolution is only limited by the 70 nm focal spot at 13 keV X-ray energy. Also, the 3D capabilities of this instrument are demonstrated by performing holotomography on a chalk sample at a mesoscale resolution of around 155 nm. It is foreseen that in-line holography will broaden the spectra of capabilities of MAX IV by providing fast 2D and 3D electron density images from mesoscale down to nanoscale resolution.
|
|
| 8. |
- Zhang, Zhaojun, et al.
(author)
-
Single-Crystalline Perovskite Nanowire Arrays for Stable X-ray Scintillators with Micrometer Spatial Resolution
- 2022
-
In: ACS Applied Nano Materials. - : American Chemical Society (ACS). - 2574-0970. ; 5:1, s. 881-889
-
Journal article (peer-reviewed)abstract
- X-ray scintillation detectors based on metal halide perovskites have shown excellent light yield, but they mostly target applications with spatial resolution at the tens of micrometers level. Here, we use a one-step solution method to grow arrays of 15-μm-long single-crystalline CsPbBr3 nanowires (NWs) in an AAO (anodized aluminum oxide) membrane template, with nanowire diameters ranging from 30 to 360 nm. The CsPbBr3 nanowires in AAO (CsPbBr3 NW/AAO) show increasing X-ray scintillation efficiency with decreasing nanowire diameter, with a maximum photon yield of ∼5 »300 ph/MeV at 30 nm diameter. The CsPbBr3 NW/AAO composites also display high radiation resistance, with a scintillation-intensity decrease of only ∼20-30% after 24 h of X-ray exposure (integrated dose 162 Gyair) and almost no change after ambient storage for 2 months. X-ray images can distinguish line pairs with a spacing of 2 μm for all nanowire diameters, while slanted edge measurements show a spatial resolution of ∼160 lp/mm at modulation transfer function (MTF) = 0.1. The combination of high spatial resolution, radiation stability, and easy fabrication makes these CsPbBr3 NW/AAO scintillators a promising candidate for high-resolution X-ray imaging applications.
|
|
