| 1. |
- Andreasson, Björn Pererik, 1979-, et al.
(författare)
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Detecting oxygen vacancies in SrTiO3 by 3d transition-metal tracer ions
- 2009
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - College Park, MD : American Physical Society. - 1098-0121 .- 1550-235X. ; 80:21, s. Article number: 212103-
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Tidskriftsartikel (refereegranskat)abstract
- X-ray absorption experiments on 3d transition-metal tracer ions in SrTiO3 are presented. The absorption spectra of the tracer-ion changed upon reduction in the SrTiO3. This change is due to an oxygen vacancy created at the tracer-ion site. This finding is supported by density-functional theory calculations, which prove that the oxygen vacancies preferentially are created at the tracer-ion sites. Using the chemical sensitivity of x-ray absorption spectroscopy, tracer ions can be used to detect oxygen vacancies in SrTiO3 and possibly in other oxide systems. © 2009 The American Physical Society.
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| 2. |
- Andreasson, Björn Pererik, 1979-, et al.
(författare)
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Origin of oxygen vacancies in resistive switching memory devices
- 2009
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Ingår i: Journal of Physics, Conference Series. - Bristol : Institute of Physics Publishing (IOPP). - 1742-6588 .- 1742-6596. ; 190, s. Article number: 012074-
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Tidskriftsartikel (refereegranskat)abstract
- The resistive switching state in Cr-doped SrTiO3 was induced by applying an electric field. This was done in ambient air and in an atmosphere of H2/Ar. The distribution of the thereby introduced oxygen vacancies was studied by spatially resolved X-ray fluorescence images. It was concluded that the oxygen vacancies were introduced in the interface between the SrTiO3 and the positively biased electrode. © 2009 IOP Publishing Ltd.
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| 3. |
- Andreasson, Björn Pererik, 1979-, et al.
(författare)
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Resistive switching in Cr-doped SrTiO3 : An X-ray absorption spectroscopy study
- 2007
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Ingår i: Materials Science & Engineering. - Amsterdam : Elsevier. - 0921-5107 .- 1873-4944. ; 144:1-3, s. 60-63
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Tidskriftsartikel (refereegranskat)abstract
- X-ray absorption spectroscopy was used to study the microscopic origin of conductance and resistive switching in chromium-doped strontium titanate (Cr:SrTiO3). Differences in the X-ray absorption near edge spectroscopy (XANES) at the Cr K-edge indicate that the valence of Cr changes from 3+ to 4+ underneath the anode of our sample device after the application of an electric field. Spatially resolved X-ray fluorescence microscopy (μ-XRF) maps show that the Cr4+ region retracts from the anode-Cr:SrTiO3 interface after a conducting state has been achieved. This interface region is studied with extended X-ray absorption fine structure (EXAFS) and the results are compared with structural parameters obtained from density functional theory (DFT) calculations. They confirm that oxygen vacancies which are localized at the octahedron with a Cr at its center are introduced at the interface. It is proposed that the switching state is not due to a valence change of chromium but caused by changes of oxygen vacancies at the interface. © 2007 Elsevier B.V. All rights reserved.
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| 4. |
- Andreasson, Björn Pererik, 1979-, et al.
(författare)
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Spatial distribution of oxygen vacancies in Cr-doped SrTiO3 during an electric-field-driven insulator-to-metal transition
- 2009
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Ingår i: Applied Physics Letters. - College Park, MD : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 94:1, s. Article number: 013513-
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Tidskriftsartikel (refereegranskat)abstract
- Spatially resolved x-ray fluorescence maps are presented that show the introduction and the evolution of oxygen vacancies in chromium-doped strontium titanate during an electric-field-driven insulator-to-metal transition. The vacancies are introduced at the anode and diffuse through the crystal toward the cathode. The spatial distribution of vacancies is explained by a model describing the electrical breakdown as a percolation process. Strong differences in the vacancy distribution were found when the transition took place in air and in a hydrogen-enriched atmosphere. In air, the vacancies disappeared from the surface, whereas in the reducing hydrogen atmosphere, they remained at the surface. © 2009 American Institute of Physics.
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| 5. |
- Friel, Ross, Dr, 1982-, et al.
(författare)
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3D Printed Radar Lenses with Anti-Reflective Structures
- 2019
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Ingår i: Designs. - Basel : MDPI. - 2411-9660. ; 3:2
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Tidskriftsartikel (refereegranskat)abstract
- Background: The purpose of this study was to determine if 3D printed lenses with wavelength specific anti-reflective (AR) surface structures would improve beam intensity and thus radar efficiency for a Printed Circuit Board (PCB)-based 60 GHz radar. This would have potential for improved low-cost radar lenses for the consumer product market. Methods: A hyperbolic lens was designed in 3D Computer Aided Design (CAD) software and was then modified with a wavelength specified AR structure. Electromagnetic computer simulation was performed on both the ‘smooth’ and ‘AR structure’ lenses and compared to actual 60 GHz radar measurements of 3D printed polylactic acid (PLA) lenses. Results: The simulation results showed an increase of 10% in signal intensity of the AR structure lens over the smooth lens. Actual measurement showed an 8% increase in signal of the AR structure lens over the smooth lens. Conclusions: Low cost and readily available Fused Filament Fabrication (FFF) 3D printing has been shown to be capable of printing an AR structure coated hyperbolic lens for millimeter wavelength radar applications. These 3D Printed AR structure lenses are effective in improving radar measurements over non-AR structure lenses. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.
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| 6. |
- Guarese, Renan, et al.
(författare)
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A proposal for augmented situated visualization towards EMC testing
- 2020
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Ingår i: CEUR Workshop Proceedings. - : CEUR-WS. ; , s. 12-15
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Konferensbidrag (refereegranskat)abstract
- Copyright © 2020 for this paper by its authors.In EMC testing, 3D electromagnetic field data often needs to be visually analysed by an expert in order to detect product defects or unwanted interference between multiple devices. In this sense, the present work proposes the use of data visualization techniques allied to an Augmented Reality user interface to provide information that helps professionals to analyse the same data, however spatially situated where it was first measured. Apart from visualizing it, users may also interact with the data to narrow down their search by switching the attributes being displayed, combining them together, applying filters or changing the formatting in which data is presented. The approaches being proposed in this work will ultimately be tested against each other in comparable 2D and 3D interactive visualizations of the same data in a series of usability assessments with users to validate the solutions. The goal is to ultimately expose whether AR can help users to make more accurate decisions, particularly in EMC related tasks.
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| 7. |
- Guarese, Renan, et al.
(författare)
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Augmented situated visualization methods towards electromagnetic compatibility testing
- 2021
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Ingår i: Computers & graphics. - Oxford : Elsevier. - 0097-8493 .- 1873-7684. ; 94, s. 1-10
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Tidskriftsartikel (refereegranskat)abstract
- In electrical engineering, hardware experts often need to analyze electromagnetic radiation data to detect any external interference or anomaly. The field that studies this sort of assessment is called electromagnetic compatibility (EMC). As a way to support EMC analysis, we propose the use of Augmented Situated Visualization (ASV) to supply professionals with visual and interactive information that helps them to comprehend that data, however situating it where it is most relevant in its spatial context. Users are able to interact with the visualization by changing the attributes being displayed, comparing the overlaps of multiple fields, and extracting data, as a way to refine their search. The solutions being proposed in this work were tested against each other in comparable 2D and 3D interactive visualizations of the same data in a series of data-extraction assessments with users, as a means to validate the approaches. Results exposed a correctness-time trade-off between the interaction methods. The hand-based techniques (Hand Slider and Touch Lens) were the least error-prone, being near to half as error-inducing as the gaze-based method. Touch Lens also performed as the least time-consuming method, taking in average less than half of the average time required by the others. For the visualization methods tested, the 2D ray casts presented a higher usability score and lesser workload index than the 3D topology view, however exposing over two times the error ratio. Ultimately, this work exposes how AR can help users to have better performances in a decision-making context, particularly in EMC related tasks, while also furthering the research in the ASV field. © 2020 Elsevier Ltd
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| 8. |
- Hagström, A. L., et al.
(författare)
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An iterative approach to determine the refractive index of 3D printed 60GHz PLA lenses
- 2018
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Ingår i: Proceedings of the 14th Loughborough Antennas and Propagation Conference (LAPC 2018). - Piscataway, N.J. : IEEE. - 9781785619694
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Konferensbidrag (refereegranskat)abstract
- This paper describes an iterative approach to determine quasi-optical properties of standard 3D printer filament material to, in an inexpensive and fast way, construct focusing lenses for millimetre wave systems. Results from three lenses with different focal lengths are shown and discussed. The real part of the permittivity at 60GHz for polylactic acid (PLA) is in this paper determined to be εr=2.74. © 2018 Institution of Engineering and Technology. All rights reserved.
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| 9. |
- Iqbal, Amjad, et al.
(författare)
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SIW-based frequency-adjustable antenna for IoT-based duplex wireless devices
- 2024
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Ingår i: AEU - International Journal of Electronics and Communications. - München : Elsevier. - 1434-8411 .- 1618-0399. ; 173
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Tidskriftsartikel (refereegranskat)abstract
- This paper proposes a compact and frequency-adjustable/reconfigurable dielectric (DR)-loaded eighth-mode substrate integrated waveguide (EMSIW) antenna for duplex wireless communications. The miniaturization of the resonators is realized using a rectangular slot and high isolation is achieved by keeping a reasonable space between them. The proposed design is simulated using a three-dimensional (3D) full-wave simulator, then analysed with a circuit model and finally validated experimentally. Frequency-reconfigurability in the suggested antenna is achieved by placing DRs with different permittivities in the designated holes that are realized in the open-ended portion of each resonator. Consequently, the lower- and high-resonant bands can be reconfigured from 4.70 to 5.23 GHz and from 5.55 to 6.34 GHz, respectively. It is worth mentioning that both resonant band can be independently reconfigured. Moreover, the inter-resonator coupling is always lower than −23.5 dB in the bands of interest. Furthermore, the peak realized gains are always greater than 4.7 dBi in the lower frequency band and 5.5 dBi in the higher one. The suggested antenna has stable radiation properties in both bands in all frequency ranges. Hence, this design is suitable for compact reconfigurable devices due to its compactness, large frequency ranges, stable radiation patterns, and high isolation. © 2023 Elsevier GmbH
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| 10. |
- Janousch, Markus, et al.
(författare)
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Role of oxygen vacancies in cr-doped SrTiO3 for resistance-change memory
- 2007
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Ingår i: Advanced Materials. - Weinheim : Wiley-VCH Verlagsgesellschaft. - 0935-9648 .- 1521-4095. ; 19:17, s. 2232-2235
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Tidskriftsartikel (refereegranskat)abstract
- A high density of oxygen vacancies has been found in an experiment to determine the path of electrical conduction in Cr-doped SrTiO3 memory cells. The Cr acts as a seed for the localization of oxygen vacancies, leading to a statistically homogeneous distribution of charge carriers within the path. This warrants a controllable doping profile and improved device scaling down to the nanometer scale. The combination of laterally resolved micro-X-ray absorption spectroscopy and thermal imaging concludes that the resistance switching in Cr-doped SrTiO3 originates from an oxygen-vacancy drift to/from the electrode that was used as anode during the conditioning process. The experiments shows that this oxygen vacancy concept is crucial for the entire class of transition-metal-oxide-based bipolar resistance-change memory.
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