| 1. |
- Andrade, Pedro Amarante, et al.
(författare)
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The Flow and Pressure Relationships in Different Tubes Commonly Used for Semi-occluded Vocal Tract Exercises
- 2016
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Ingår i: Journal of Voice. - : Mosby-Elsevier. - 0892-1997 .- 1873-4588. ; 30:1, s. 36-41
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Tidskriftsartikel (refereegranskat)abstract
- This experimental study investigated the back pressure (Pback) versus flow (U) relationship for 10 different tubes commonly used for semi-occluded vocal tract exercises, that is, eight straws of different lengths and diameters, a resonance tube, and a silicone tube similar to a Lax Vox tube. All tubes were assessed with the free end in air. The resonance tube and silicone tube were further assessed with the free end under water at the depths from 1 to 7 cm in steps of 1 cm. The results showed that relative changes in the diameter of straws affect Pback considerably more compared with the same amount of relative change in length. Additionally, once tubes are submerged into water, Pback needs to overcome the pressure generated by the water depth before flow can start. Under this condition, only a small increase in Pback was observed as the flow was increased. Therefore, the wider tubes submerged into water produced an almost constant Pback determined by the water depth, whereas the thinner straws in air produced relatively large changes to Pback as flow was changed. These differences may be taken advantage of when customizing exercises for different users and diagnoses and optimizing the therapy outcome.
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| 2. |
- Björling, Alexander, et al.
(författare)
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Coherent Bragg imaging of 60 nm Au nanoparticles under electrochemical control at the NanoMAX beamline
- 2019
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Ingår i: Journal of Synchrotron Radiation. - 0909-0495. ; 26, s. 1830-1834
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Tidskriftsartikel (refereegranskat)abstract
- Nanoparticles are essential electrocatalysts in chemical production, water treatment and energy conversion, but engineering efficient and specific catalysts requires understanding complex structure-reactivity relations. Recent experiments have shown that Bragg coherent diffraction imaging might be a powerful tool in this regard. The technique provides three-dimensional lattice strain fields from which surface reactivity maps can be inferred. However, all experiments published so far have investigated particles an order of magnitude larger than those used in practical applications. Studying smaller particles quickly becomes demanding as the diffracted intensity falls. Here, in situ nanodiffraction data from 60 nm Au nanoparticles under electrochemical control collected at the hard X-ray nanoprobe beamline of MAX IV, NanoMAX, are presented. Two-dimensional image reconstructions of these particles are produced, and it is estimated that NanoMAX, which is now open for general users, has the requisites for three-dimensional imaging of particles of a size relevant for catalytic applications. This represents the first demonstration of coherent X-ray diffraction experiments performed at a diffraction-limited storage ring, and illustrates the importance of these new sources for experiments where coherence properties become crucial.
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| 3. |
- Chayanun, Lert, et al.
(författare)
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Combining Nanofocused X-Rays with Electrical Measurements at the NanoMAX Beamline
- 2019
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Ingår i: Crystals. - : MDPI AG. - 2073-4352. ; 9:8
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Tidskriftsartikel (refereegranskat)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.
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| 4. |
- Chayanun, Lert, et al.
(författare)
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Nanoscale mapping of carrier collection in single nanowire solar cells using X-ray beam induced current
- 2019
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Ingår i: Journal of Synchrotron Radiation. - 0909-0495.
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Tidskriftsartikel (refereegranskat)abstract
- Here it is demonstrated how nanofocused X-ray beam induced current (XBIC) can be used to quantitatively map the spatially dependent carrier collection probability within nanostructured solar cells. The photocurrent generated by a 50 nm-diameter X-ray beam was measured as a function of position, bias and flux in single p–i–n doped solar-cell nanowires. The signal gathered mostly from the middle segment decays exponentially toward the p- and n-segments, with a characteristic decay length that varies between 50 nm and 750 nm depending on the flux and the applied bias. The amplitude of the XBIC shows saturation at reverse bias, which indicates that most carriers are collected. At forward bias, the relevant condition for solar cells, the carrier collection is only efficient in a small region. Comparison with finite element modeling suggests that this is due to unintentional p-doping in the middle segment. It is expected that nanofocused XBIC could be used to investigate carrier collection in a wide range of nanostructured solar cells.
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| 5. |
- Dzhigaev, Dmitry, et al.
(författare)
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Strain mapping inside an individual processed vertical nanowire transistor using scanning X-ray nanodiffraction
- 2020
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3372 .- 2040-3364. ; 12:27, s. 14487-14493
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Tidskriftsartikel (refereegranskat)abstract
- Semiconductor nanowires in wrapped, gate-all-around transistor geometry are highly favorable for future electronics. The advanced nanodevice processing results in strain due to the deposited dielectric and metal layers surrounding the nanowires, significantly affecting their performance. Therefore, non-destructive nanoscale characterization of complete devices is of utmost importance due to the small feature sizes and three-dimensional buried structure. Direct strain mapping inside heterostructured GaSb-InAs nanowire tunnel field-effect transistor embedded in dielectric HfO2, W metal gate layers, and an organic spacer is performed using fast scanning X-ray nanodiffraction. The effect of 10 nm W gate on a single embedded nanowire with segment diameters down to 40 nm is retrieved. The tensile strain values reach 0.26% in the p-type GaSb segment of the transistor. Supported by the finite element method simulation, we establish a connection between the Ar pressure used during the W layer deposition and the nanowire strain state. Thus, we can benchmark our models for further improvements in device engineering. Our study indicates, how the significant increase in X-ray brightness at 4th generation synchrotron, makes high-throughput measurements on realistic nanoelectronic devices viable.
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| 6. |
- Hammarberg, Susanna, et al.
(författare)
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Fast nanoscale imaging of strain in a multi-segment heterostructured nanowire with 2D Bragg ptychography
- 2024
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Ingår i: Journal of Applied Crystallography. - 0021-8898. ; 57, s. 60-70
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Tidskriftsartikel (refereegranskat)abstract
- Developing semiconductor devices requires a fast and reliable source of strain information with high spatial resolution and strain sensitivity. This work investigates the strain in an axially heterostructured 180 nm-diameter GaInP nanowire with InP segments of varying lengths down to 9 nm, simultaneously probing both materials. Scanning X-ray diffraction (XRD) is compared with Bragg projection ptychography (BPP), a fast single-projection method. BPP offers a sufficient spatial resolution to reveal fine details within the largest segments, unlike scanning XRD. The spatial resolution affects the quantitative accuracy of the strain maps, where BPP shows much-improved agreement with an elastic 3D finite element model compared with scanning XRD. The sensitivity of BPP to small deviations from the Bragg condition is systematically investigated. The experimental confirmation of the model suggests that the large lattice mismatch of 1.52% is accommodated without defects.
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| 7. |
- Hammarberg, Susanna, et al.
(författare)
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High resolution strain mapping of a single axially heterostructured nanowire using scanning X-ray diffraction
- 2020
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Ingår i: Nano Research. - : Springer Science and Business Media LLC. - 1998-0124 .- 1998-0000. ; 13:9, s. 2460-2468
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Tidskriftsartikel (refereegranskat)abstract
- Axially heterostructured nanowires are a promising platform for next generation electronic and optoelectronic devices. Reports based on theoretical modeling have predicted more complex strain distributions and increased critical layer thicknesses than in thin films, due to lateral strain relaxation at the surface, but the understanding of the growth and strain distributions in these complex structures is hampered by the lack of high-resolution characterization techniques. Here, we demonstrate strain mapping of an axially segmented GaInP-InP 190 nm diameter nanowire heterostructure using scanning X-ray diffraction. We systematically investigate the strain distribution and lattice tilt in three different segment lengths from 45 to 170 nm, obtaining strain maps with about 10−4 relative strain sensitivity. The experiments were performed using the 90 nm diameter nanofocus at the NanoMAX beamline, taking advantage of the high coherent flux from the first diffraction limited storage ring MAX IV. The experimental results are in good agreement with a full simulation of the experiment based on a three-dimensional (3D) finite element model. The largest segments show a complex profile, where the lateral strain relaxation at the surface leads to a dome-shaped strain distribution from the mismatched interfaces, and a change from tensile to compressive strain within a single segment. The lattice tilt maps show a cross-shaped profile with excellent qualitative and quantitative agreement with the simulations. In contrast, the shortest measured InP segment is almost fully adapted to the surrounding GaInP segments. [Figure not available: see fulltext.].
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| 8. |
- Hammarberg, Susanna, et al.
(författare)
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Nanoscale X-ray Imaging of Composition and Ferroelastic Domains in Heterostructured Perovskite Nanowires : Implications for Optoelectronic Devices
- 2023
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Ingår i: ACS Applied Nano Materials. - 2574-0970. ; 6:19, s. 17698-17705
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Tidskriftsartikel (refereegranskat)abstract
- Metal halide perovskites (MHPs) have garnered significant interest as promising candidates for nanoscale optoelectronic applications due to their excellent optical properties. Axially heterostructured CsPbBr3-CsPb(Br(1-x)Clx)3 nanowires can be produced by localized anion exchange of pregrown CsPbBr3 nanowires. However, characterizing such heterostructures with sufficient strain and real space resolution is challenging. Here, we use nanofocused scanning X-ray diffraction (XRD) and X-ray fluorescence (XRF) with a 60 nm beam to investigate a heterostructured MHP nanowire as well as a reference CsPbBr3 nanowire. The nano-XRD approach gives spatially resolved maps of composition, lattice spacing, and lattice tilt. Both the reference and exchanged nanowire show signs of diverse types of ferroelastic domains, as revealed by the tilt maps. The chlorinated segment shows an average Cl composition of x = 66 and x = 70% as measured by XRD and XRF, respectively. The XRD measurements give a much more consistent result than the XRF ones. These findings are consistent with photoluminescence measurements, showing x = 73%. The nominally unexchanged segment also has a small concentration of Cl, as observed with all three methods, which we attribute to diffusion after processing. These results highlight the need to prevent such unwanted processes in order to fabricate optoelectronic devices based on MHP heterostructures.
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| 9. |
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| 10. |
- Hammarberg, Susanna
(författare)
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Strain Mapping of Single Nanowires using Nano X-ray Diffraction
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Nanowires are explored as basic components for a large range of electronic devices. The nanowire format offersseveral benefits, including reduced material consumption and increased potential for combining materials to formnew novel heterostructures. Several factors, such as mechanical stress from contacting or a lattice mismatch in aheterostructure, can strain and change the lattice tilt. The strain is often intertwined with small gradients ofcomposition. The strain relaxation can differ significantly from bulk due to the small diameters, but the mechanismsare not fully comprehended. X-rays have a penetrating power that makes it possible to investigate embeddedsamples without preparation or slicing. The high flux of coherent X-ray beams from synchrotron radiation facilities,combined with the nano-focus capabilities developed in recent years, have made it possible to probe nano-crystals.The 4th generation of synchrotrons, including MAX IV in Lund, Sweden, has even higher brilliance than previoussources. Diffraction imaging techniques using synchrotron radiation can reveal small strains down to 10-4-10-5. Thefield of coherent imaging pushes the limits of resolutions below the size of the focus. With Bragg ptychography, thedisplacement field in a crystal can be probed with resolution beyond the probe focus by numerically reconstructingthe phase.This thesis includes the development of X-ray nano-diffraction methods for the characterizing of nanowires, includingGaInP/InP barcode nanowires, p-i-n InP nanowire devices and metal halide perovskite CsPbBr3 nanowires. Itincludes a theoretical background of the scattering mechanisms in Thomson scattering in nano-crystals, goesthrough the formalism for coherent diffraction imaging, crystal structure and deformation in nanoobjects and thetechnical aspects of the experimental setup and measurement. Moreover, theoretical modelling of elastic strainrelaxation in these nanowires was performed with finite element modelling.Single III-V nanowire heterostructures and III-V nanowire devices were probed with scanning XRD and Braggprojection ptychography (BPP). How the techniques compare to each other and how the results are affected by thedifferent approximations that are made in the respective technique was explored. Finite element simulationscombined with nano-diffraction revealed that the lattice mismatch of 1.5% could be relaxed elastically for thediameter of 180 nm. From the strain mapping of the nanowire device, we found how the contacting of the nanowirebends the nanowire resulting in a tilt normal to the substrate.Single perovskite metal-halide perovskite CsPb(Br(1-x)Clx)3 nanowire heterostructures were characterized withscanning nano-XRD and XRF, which showed that the lattice spacing was affected by composition and strain.Composition gradients revealed that Cl diffusion had taken place within the heterostructure. Furthermore, extractingthe lattice tilts from shifts of the Bragg peak revealed a ferroelastic domain structure with simultaneously existinglattice tilts. These findings are beneficial for the further development of MHP nanowires devices.
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