| 1. |
- Buchanan, E. M., et al.
(författare)
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The Psychological Science Accelerator's COVID-19 rapid-response dataset
- 2023
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Ingår i: Scientific Data. - : Springer Science and Business Media LLC. - 2052-4463. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- In response to the COVID-19 pandemic, the Psychological Science Accelerator coordinated three large-scale psychological studies to examine the effects of loss-gain framing, cognitive reappraisals, and autonomy framing manipulations on behavioral intentions and affective measures. The data collected (April to October 2020) included specific measures for each experimental study, a general questionnaire examining health prevention behaviors and COVID-19 experience, geographical and cultural context characterization, and demographic information for each participant. Each participant started the study with the same general questions and then was randomized to complete either one longer experiment or two shorter experiments. Data were provided by 73,223 participants with varying completion rates. Participants completed the survey from 111 geopolitical regions in 44 unique languages/dialects. The anonymized dataset described here is provided in both raw and processed formats to facilitate re-use and further analyses. The dataset offers secondary analytic opportunities to explore coping, framing, and self-determination across a diverse, global sample obtained at the onset of the COVID-19 pandemic, which can be merged with other time-sampled or geographic data.
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| 2. |
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| 3. |
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| 4. |
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| 5. |
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| 6. |
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| 7. |
- Sawicki, M., et al.
(författare)
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Homogeneous and heterogeneous magnetism in (Zn,Co)O : From a random antiferromagnet to a dipolar superferromagnet by changing the growth temperature
- 2013
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 88:8
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Tidskriftsartikel (refereegranskat)abstract
- A series of (Zn,Co)O layers with Co contents x up to 40% grown by atomic layer deposition have been investigated. All structures deposited at 160 degrees C show magnetic properties specific to II-VI dilute magnetic semiconductors with localized spins S = 3/2 coupled by strong but short-range antiferromagnetic interactions resulting in low-temperature spin-glass freezing for x = 0.16 and 0.4. At higher growth temperature (200 degrees C) metallic Co nanocrystals precipitate in two locations giving rise to two different magnetic responses: (i) a superparamagnetic contribution coming from volume disperse nanocrystals; (ii) a ferromagneticlike behavior brought about by nanocrystals residing at the (Zn,Co)O/substrate interface. It is shown that the dipolar coupling within the interfacial two-dimensional dense dispersion of nanocrystals is responsible for the ferromagneticlike behavior.
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| 8. |
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| 9. |
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| 10. |
- ASPELMEIER, A, et al.
(författare)
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AC SUSCEPTIBILITY MEASUREMENTS OF MAGNETIC MONOLAYERS - MCXD, MOKE, AND MUTUAL INDUCTANCE
- 1995
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Ingår i: JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS. - : ELSEVIER SCIENCE BV. - 0304-8853. ; 146:3, s. 256-266
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Tidskriftsartikel (refereegranskat)abstract
- A refined analysis of dispersive and absorptive contributions to the complex magnetic susceptibility yields detailed information on magnetic and structural properties of ultrathin films. The new ac modulated magnetic circular X-ray dichroism (MCXD) techni
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| 11. |
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| 12. |
- Sridhar, Arun R., et al.
(författare)
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Identifying Risk of Adverse Outcomes in COVID-19 Patients via Artificial Intelligence-Powered Analysis of 12-Lead Intake Electrocardiogram.
- 2022
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Ingår i: Cardiovascular digital health journal. - : Elsevier. - 2666-6936. ; 3:2, s. 62-74
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Tidskriftsartikel (refereegranskat)abstract
- Background: Adverse events in COVID-19 are difficult to predict. Risk stratification is encumbered by the need to protect healthcare workers. We hypothesize that AI can help identify subtle signs of myocardial involvement in the 12-lead electrocardiogram (ECG), which could help predict complications.Objective: Use intake ECGs from COVID-19 patients to train AI models to predict risk of mortality or major adverse cardiovascular events (MACE).Methods: We studied intake ECGs from 1448 COVID-19 patients (60.5% male, 63.4±16.9 years). Records were labeled by mortality (death vs. discharge) or MACE (no events vs. arrhythmic, heart failure [HF], or thromboembolic [TE] events), then used to train AI models; these were compared to conventional regression models developed using demographic and comorbidity data.Results: 245 (17.7%) patients died (67.3% male, 74.5±14.4 years); 352 (24.4%) experienced at least one MACE (119 arrhythmic; 107 HF; 130 TE). AI models predicted mortality and MACE with area under the curve (AUC) values of 0.60±0.05 and 0.55±0.07, respectively; these were comparable to AUC values for conventional models (0.73±0.07 and 0.65±0.10). There were no prominent temporal trends in mortality rate or MACE incidence in our cohort; holdout testing with data from after a cutoff date (June 9, 2020) did not degrade model performance.Conclusion: Using intake ECGs alone, our AI models had limited ability to predict hospitalized COVID-19 patients' risk of mortality or MACE. Our models' accuracy was comparable to that of conventional models built using more in-depth information, but translation to clinical use would require higher sensitivity and positive predictive value. In the future, we hope that mixed-input AI models utilizing both ECG and clinical data may be developed to enhance predictive accuracy.
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| 13. |
- Ethier, J-F., et al.
(författare)
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Clinical Data Integration Model : Core Interoperability Ontology for Research Using Primary Care Data
- 2015
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Ingår i: Methods of Information in Medicine. - 0026-1270 .- 2511-705X. ; 54:1, s. 16-23
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: This article is part of the Focus Theme of Methods of Information in Medicine on "Managing Interoperability and Complexity in Health Systems". Background: Primary care data is the single richest source of routine health care data. However its use, both in research and clinical work, often requires data from multiple clinical sites, clinical trials databases and registries. Data integration and interoperability are therefore of utmost importance. Objectives: TRANSFoRm's general approach relies on a unified interoperability frame-work, described in a previous paper. We developed a core ontology for an interoperability framework based on data mediation. This article presents how such an ontology, the Clinical Data Integration Model (CDIM), can be designed to support, in conjunction with appropriate terminologies, biomedical data federation within TRANSFoRm, an EU FP7 project that aims to develop the digital infrastructure for a learning healthcare system in European Primary Care. Methods: TRANSFoRm utilizes a unified structural /terminological interoperability framework, based on the local-as-view mediation paradigm. Such an approach mandates the global information model to describe the domain of interest independently of the data sources to be explored. Following a requirement analysis process, no ontology focusing on primary care research was identified and, thus we designed a realist ontology based on Basic Formal Ontology to support our framework in collaboration with various terminologies used in primary care. Results: The resulting ontology has 549 classes and 82 object properties and is used to support data integration for TRANSFoRm's use cases. Concepts identified by researchers were successfully expressed in queries using CDIM and pertinent terminologies. As an example, we illustrate how, in TRANSFoRm, the Query Formulation Workbench can capture eligibility criteria in a computable representation, which is based on CDIM. Conclusion: A unified mediation approach to semantic interoperability provides a flexible and extensible framework for all types of interaction between health record systems and research systems. CDIM, as core ontology of such an approach, enables simplicity and consistency of design across the heterogeneous software landscape and can support the specific needs of EHR-driven phenotyping research using primary care data.
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| 14. |
- MAY, F, et al.
(författare)
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AN ANGLE-DEPENDENT MAGNETIC CIRCULAR X-RAY DICHROISM STUDY OF CO/CU(100) - EXPERIMENT VERSUS THEORY
- 1995
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Ingår i: JOURNAL OF PHYSICS-CONDENSED MATTER. - : IOP PUBLISHING LTD. - 0953-8984. ; 7:6, s. 1111-1119
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Values for the magnetic moments of 3d transition metals have been calculated from magnetic circular x-ray dichroism measurements using sum rules. In this work we reveal that these calculations are sensitive to a damping effect resulting from a decrease in
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| 15. |
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| 16. |
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| 17. |
- TISCHER, M, et al.
(författare)
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LOCAL MAGNETISM AND ELEMENT-SPECIFIC SUSCEPTIBILITY FOR NI/CU(100)
- 1995
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Ingår i: VACUUM. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0042-207X. ; 46:8-10, s. 1211-1214
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- We report magnetic circular X-ray dichroism (MCXD) measurements of ultrathin Ni films grown on Cu(?OO). The Curie temperature of the films is determined by means of a.c. MXCD susceptibility, a technique that allows T-c to be probed precisely and unambiguo
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| 18. |
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| 19. |
- ARVANITIS, D, et al.
(författare)
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PAIR POTENTIALS IN THE SEXAFS ANALYSIS
- 1995
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Ingår i: PHYSICA B. - : ELSEVIER SCIENCE BV. - 0921-4526. ; 209:1-4, s. 431-435
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- An overview for a dynamical SEXAFS analysis for several systems is presented in terms of effective pair potentials. Model potentials of Madelung type are found to describe well the adsorption of N, O, O-2 on Cu and Ni metal surfaces. The potential paramet
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| 20. |
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| 21. |
- Delaney, BC, et al.
(författare)
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Translational Medicine and Patient Safety in Europe: TRANSFoRm--Architecture for the Learning Health System in Europe
- 2015
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Ingår i: BioMed research international. - : Hindawi Limited. - 2314-6141 .- 2314-6133. ; 2015, s. 961526-
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Tidskriftsartikel (refereegranskat)abstract
- The Learning Health System (LHS) describes linking routine healthcare systems directly with both research translation and knowledge translation as an extension of the evidence-based medicine paradigm, taking advantage of the ubiquitous use of electronic health record (EHR) systems. TRANSFoRm is an EU FP7 project that seeks to develop an infrastructure for the LHS in European primary care.Methods. The project is based on three clinical use cases, a genotype-phenotype study in diabetes, a randomised controlled trial with gastroesophageal reflux disease, and a diagnostic decision support system for chest pain, abdominal pain, and shortness of breath.Results. Four models were developed (clinical research, clinical data, provenance, and diagnosis) that form the basis of the projects approach to interoperability. These models are maintained as ontologies with binding of terms to define precise data elements. CDISC ODM and SDM standards are extended using an archetype approach to enable a two-level model of individual data elements, representing both research content and clinical content. Separate configurations of the TRANSFoRm tools serve each use case.Conclusions.The project has been successful in using ontologies and archetypes to develop a highly flexible solution to the problem of heterogeneity of data sources presented by the LHS.
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| 22. |
- Gill, Dipender, et al.
(författare)
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ACE inhibition and cardiometabolic risk factors, lung ACE2 and TMPRSS2 gene expression, and plasma ACE2 levels : a Mendelian randomization study
- 2020
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Ingår i: Royal Society Open Science. - : ROYAL SOC. - 2054-5703. ; 7:11
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Tidskriftsartikel (refereegranskat)abstract
- Angiotensin-converting enzyme 2 (ACE2) and serine protease TMPRSS2 have been implicated in cell entry for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus responsible for coronavirus disease 2019 (COVID-19). The expression of ACE2 and TMPRSS2 in the lung epithelium might have implications for the risk of SARS-CoV-2 infection and severity of COVID-19. We use human genetic variants that proxy angiotensin-converting enzyme (ACE) inhibitor drug effects and cardiovascular risk factors to investigate whether these exposures affect lung ACE2 and TMPRSS2 gene expression and circulating ACE2 levels. We observed no consistent evidence of an association of genetically predicted serum ACE levels with any of our outcomes. There was weak evidence for an association of genetically predicted serum ACE levels with ACE2 gene expression in the Lung eQTL Consortium (p = 0.014), but this finding did not replicate. There was evidence of a positive association of genetic liability to type 2 diabetes mellitus with lung ACE2 gene expression in the Gene-Tissue Expression (GTEx) study (p = 4 x 10(-4)) and with circulating plasma ACE2 levels in the INTERVAL study (p = 0.03), but not with lung ACE2 expression in the Lung eQTL Consortium study (p = 0.68). There were no associations of genetically proxied liability to the other cardiometabolic traits with any outcome. This study does not provide consistent evidence to support an effect of serum ACE levels (as a proxy for ACE inhibitors) or cardiometabolic risk factors on lung ACE2 and TMPRSS2 expression or plasma ACE2 levels.
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| 23. |
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| 24. |
- Gridneva, Lidia, et al.
(författare)
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Experimental investigation of the spin reorientation of Co/Au based magnetic nanodot arrays
- 2008
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121 .- 1550-235X. ; 77:10
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Tidskriftsartikel (refereegranskat)abstract
- (Co/Au) and (Au/ Co/ Au) nanomagnet arrays grown on nanostructured self-organized SiGe templates have been characterized by means of x-ray photoemission electron microscopy, x-ray magnetic circular dichroism, and by extended x-ray absorption spectroscopy using synchrotron radiation. In-plane magnetization is observed at room temperature for practically all Co thicknesses, a stable macroscopic perpendicular magnetic order only at low temperature. The spin reorientation transition in these dot arrays takes place for smaller Co thicknesses over a broader thickness range than in two-dimensional systems. This finding appears to be related with structural relaxation modifications, occurring within the local Co atom environment, which are not necessarily connected with the orbital moment variations. These variations appear in the form of a systematic increase, correlated with the existence of out-of-plane magnetization.
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| 25. |
- Ivanov, Sergey A., et al.
(författare)
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Structural and magnetic properties of nickel antimony ferrospinels
- 2015
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Ingår i: Materials Chemistry and Physics. - : Elsevier BV. - 0254-0584 .- 1879-3312. ; 158, s. 127-137
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Tidskriftsartikel (refereegranskat)abstract
- Spinel-type compounds of Fe-Ni-Sb-O system were synthesized as polycrystalline powders. The crystal and magnetic properties were investigated using X-ray and neutron powder diffraction, Mossbauer and X-ray absorption spectroscopy and magnetization measurements. The samples crystallize in the cubic system, space group Fd - 3 m. The distribution of cations between octahedral and tetrahedral sites was refined from the diffraction data sets using constraints imposed by the magnetic, Mossbauer and EDS results and the ionic radii. The cation distribution and the temperature dependence of the lattice parameter (a) and the oxygen positional parameter (u) were obtained. A chemical formula close to Fe0.8Ni1.8Sb0.4O4 was determined, with Sb5+ cations occupying octahedral sites, and Fe3+ and Ni2+ occupying both tetrahedral and octahedral sites. Fe3+ mainly (85/15 ratio) occupy tetrahedral sites, and conversely Ni2+ mainly reside on octahedral ones. The magnetic unit cell is the same as the crystallographic one, having identical symmetry relations. The results indicate that the compounds have a collinear ferrimagnetic structure with antiferromagnetic coupling between the tetrahedral (A) and octahedral (B) sites. Uniquely, the temperature dependence of the net magnetization of this rare earth free ferrimagnet exhibits a compensation point.
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| 26. |
- Kowalik, I. A., et al.
(författare)
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Element-specific characterization of heterogeneous magnetism in (Ga,Fe)N films
- 2012
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 85:18, s. 184411-
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Tidskriftsartikel (refereegranskat)abstract
- We employ x-ray spectroscopy to characterize the distribution and magnetism of particular alloy constituents in (Ga,Fe)N films grown by metal organic vapor phase epitaxy. Furthermore, photoelectron microscopy gives direct evidence for the aggregation of Fe ions, leading to the formation of Fe-rich nanoregions adjacent to the samples surface. A sizable x-ray magnetic circular dichroism (XMCD) signal at the Fe L edges in remanence and at moderate magnetic fields at 300 K links the high-temperature ferromagnetism with the Fe(3d) states. A sizable value of the orbital moment measured in remanence points to a large magnetic anisotropy and to a correspondingly high blocking temperature, which can stabilize the ferromagnetic-like response of the Fe-rich nanocrystals at 300 K. The XMCD response at the N K edge highlights that the N(2p) states, due to exchange coupling to Fe ions, carry considerable spin polarization. These results, supported by ab initio studies of XMCD spectra for various FeN delta nanocrystals, demonstrate that nanocrystals with delta > 0.25 account for the ferromagnetic behavior of (Ga,Fe)N films.
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| 27. |
- Kowalik, I. A., et al.
(författare)
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Soft x-ray absorption spectroscopy on Co doped ZnO : structural distortions and electronic structure
- 2016
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Ingår i: 16th International Conference On X-Ray Absorption Fine Structure (XAFS16). - : IOP Publishing.
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Konferensbidrag (refereegranskat)abstract
- We present soft x-ray absorption spectra from a series of Co doped ZnO films. We discuss systematic variations of the Co L-edge white line intensity and multiplet features for this series of samples. We document sizeable differences in the electronic state of the Co ionic cores, as well as in the local environment of the host lattice atoms, characterised by means of x-ray absorption spectra at the O K-edge and Zn L-edges. Model calculations allow to correlate the observed effects to small structural distortions of the ZnO lattice.
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| 28. |
- May, F, et al.
(författare)
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Magnetic coupling of Ni, Cu and Co bi- and trilayers probed by magnetic circular X-ray dichroism
- 1997
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Ingår i: JOURNAL DE PHYSIQUE IV. - : EDITIONS PHYSIQUE. - 1155-4339. ; 7:C2, s. 389-395
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Using magnetic circular X-ray dichroism (MCXD), Co/Ni, Cu/Co and Cu/Ni bilayers and Co/Cu/Ni and Ni/Cu/Co trilayers grown on a Cu(001) substrate were investigated. The Co layers were about 2 monolayers (Mi,) and the Ni layers were between 1.5 and 4.5 ML t
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| 29. |
- Mulders, A. M., et al.
(författare)
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On The Interface Magnetism Of Thin Oxidized Co Films : Orbital And Spin Moments
- 2009
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Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 21:12, s. 124211-
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Tidskriftsartikel (refereegranskat)abstract
- An x-ray magnetic circular dichroism study of a polycrystalline Co/CoO bilayer is presented. Using both the chemical specificity and surface sensitivity in the core level techniques, we find that uncompensated Co2+ spin moments participate in the remanent ferromagnetic response of the bilayer that has oxygen nearest neighbors. These are likely located at the Co/CoO interface. As intermixing of magnetic species is not present in Co/CoO, it is concluded that the observed interface moments are due to interface roughness. Given their direction, these moments appear to not directly correlate to the exchange bias in these bilayers.
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| 30. |
- Racka, K., et al.
(författare)
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Growth of SiC by PVT method in the presence of cerium dopant
- 2013
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248 .- 1873-5002. ; 377, s. 88-95
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Tidskriftsartikel (refereegranskat)abstract
- The effect of the presence of CeO2 in the source material on the properties of SiC crystals grown by Physical Vapor Transport (PVT) method is investigated. The doping efficiency and, indirectly, the presence of the cerium vapour in the growth atmosphere were examined by study of structural, electrical and optical properties of the crystals. X-ray photoelectron spectroscopy shows that Ce2O3 and CeO2 coexist on the SiC post-growth surfaces. A detectable Ce incorporation is observed only in the last grown part of the crystal.
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| 31. |
- Schenk, Linda, 1980-, et al.
(författare)
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Teaching and discussing about risk : seven elements of potential significance for science education
- 2019
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Ingår i: International Journal of Science Education. - : Informa UK Limited. - 0950-0693 .- 1464-5289. ; 41:9, s. 1271-1286
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Tidskriftsartikel (refereegranskat)abstract
- The present paper takes its point of departure in risk being a relevant content for science education, and that there are many different approaches to how to incorporate it. By reviewing the academic literature on the use and definitions of risk from fields such as engineering, linguistics and philosophy, we identified key elements of the risk concept relevant for science education. Risk is a phenomenon of the future that may be conveyed by our activity, it is something that may or may not take place. Hence, at the core of risk we find uncertainty and consequence. Furthermore, the elements of probability and severity are relevant modifiers of the consequence, as well as both subject to uncertainty. Additionally, in framing, understanding and decision-making on risk, as individuals or society, we need to acknowledge that risk has both objective and subjective components, lying in the interface between knowledge and values. In this paper, we describe how these key elements were derived from the literature and derive a schematic model of the risk concept for the purpose of science education. We further discuss how this model may assist in planning, execution and evaluation of teaching activities explicitly or implicitly involving risk issues.
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| 32. |
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| 33. |
- TISCHER, M, et al.
(författare)
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ENHANCEMENT OF ORBITAL MAGNETISM AT SURFACES - CO ON CU(100)
- 1995
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Ingår i: PHYSICAL REVIEW LETTERS. - : AMER INST PHYSICS. - 0031-9007. ; 75:8, s. 1602-1605
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- By combining magnetic circular x-ray dichroism experiments with first principles electronic structure calculations, we demonstrate that the orbital contribution to magnetism can be strongly enhanced at surfaces. This effect is illustrated for Co grown on
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| 34. |
- Wende, H, et al.
(författare)
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Bond length and adsorbate vibrations of (2x3)N/Cu(110): A SEXAFS study
- 1996
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Ingår i: PHYSICAL REVIEW B-CONDENSED MATTER. - : AMER INST PHYSICS. - 0163-1829. ; 54:8, s. 5920-5926
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Temperature- and angle-dependent surface-extended x-ray-absorption fine-structure (SEXAFS) measurements on the system (2X3)N/Cu(110) are reported. Three inequivalent adsorption sites of the N atoms within the surface unit cell are identified. The successf
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| 35. |
- Wende, H, et al.
(författare)
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Surface atomic-XAFS for nitrogen atoms on copper
- 1997
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Ingår i: JOURNAL DE PHYSIQUE IV. - : EDITIONS PHYSIQUE. - 1155-4339. ; 7:C2, s. 211-212
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The presence of oscillatory structures in the atomic x-ray absorption background is reported for the first time for surface EXAFS of c(2x2)NiCu(100) and (2x3)N/Cu(110). The experimental data for N/Cu(110) are compared to FEFF7 calculations of the oscillat
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| 36. |
- Wessely, Ola, et al.
(författare)
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Initial and final state effects in the x-ray absorption process of La1-xSrxMnO3
- 2003
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Ingår i: Physical Review B : Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 68:23, s. 235109-1
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Tidskriftsartikel (refereegranskat)abstract
- We have probed the electronic structure of La1-xSrxMnO3 using x-ray absorption spectroscopy, and compared our results to theory. It is shown that the O projected spectrum reveals a signal that is consistent only with hybridized and delocalized Mn d-states whereas the Mn projected spectrum reveals a signal that can only be reproduced by atomic like theory allowing for multiplet formation between the core hole and the valence electrons of the final state. Our results indicate that the ground state electronic structure has delocalized Mn d-states. This is discussed to be caused by a dynamical screening of the core hole created in the absorption process.
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| 37. |
- Wolska, A., et al.
(författare)
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Structural and magnetic properties of Mn(+) implanted silicon crystals studied using X-ray absorption spectroscopy techniques
- 2011
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Ingår i: Radiation Physics and Chemistry. - : Elsevier BV. - 0969-806X .- 1879-0895. ; 80:10, s. 1119-1124
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Tidskriftsartikel (refereegranskat)abstract
- The implantation of Mn ions into two Si substrates with different doping (P or B), resistivity and oxygen content was performed at low and high substrate temperatures. Different post-implantation processing was carried out to study its influence on the structural and magnetic properties of these samples. The local order around the Mn atoms was characterized by X-ray absorption fine structure techniques and the magnetic properties of the Mn ionic cores were determined by means of X-ray magnetic circular dichroism measurements. The results are discussed in relation to the structural and macroscopic magnetic properties. It is shown that the amorphous matrix speeds up the formation of MnSi(x) inclusions. However, the existence of inclusions or the type of electrically active dopants is not directly related to the magnetic properties. Therefore, in the performed studies, the importance of structural defects on the magnetic properties was confirmed. A localized magnetic moment carried by the Mn ionic cores could not be detected by means of dichroic measurements.
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| 38. |
- Wolska, A., et al.
(författare)
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Study of the Local Environment of Mn Ions Implanted in GaSb
- 2010
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Ingår i: Acta Physica Polonica. A. - 0587-4246 .- 1898-794X. ; 117:2, s. 286-292
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Tidskriftsartikel (refereegranskat)abstract
- The first attempts to establish an implantation process leading to formation of ferromagnetic inclusions inside the GaSb matrix are presented. Gallium antimonide containing ferromagnetic MnSb precipitations is considered as a promising material for novel spintronic applications. It is possible to obtain such inclusions during the molecular beam epitaxy (MBE) growth. However, for commercial application it would be also important to find an optimal way of producing this kind of inclusions by Mn ions implantation. In order to achieve this goal, several parameters of implantation and post annealing procedures were tested. The ion energy was kept at 10 keV or 150 keV and four different ion doses were applied, as well as various annealing conditions. The analysis of X-ray absorption spectra allowed to estimate the local atomic order around Mn atoms. Depending on the implantation energy and annealing processes, the manganese oxides or manganese atoms located in a heavily defected GaSb matrix were observed. The performed analysis helped in indicating the main obstacles in formation of MnSb inclusions inside the GaSb matrix by Mn ion implantation.
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| 39. |
- Wolska, A., et al.
(författare)
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XANES studies of Mn K and L-3,L-2 edges in the (Ga,Mn) As layers modified by high temperature annealing
- 2008
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Ingår i: Acta Physica Polonica. A. - 0587-4246 .- 1898-794X. ; 114:2, s. 357-366
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Tidskriftsartikel (refereegranskat)abstract
- Ga1-xMnx As is commonly considered as a promising material for microelectronic applications utilizing the electron spin. One of the ways that allow increasing the Curie temperature above room temperature is to produce second phase inclusions. In this paper Gal-,Mn.As samples containing precipitations of ferromagnetic MnAs are under consideration. We focus on the atomic and electronic structure around the Mn atoms relating to the cluster formation. The changes in the electronic structure of the Mn, Ga and As atoms in the (Ga,Mn)As layers after high temperature annealing were determined by X-ray absorption near edge spectroscopy. The experimental spectra were compared with the predictions of ab initio full multiple scattering theory using the FEFF 8.4 code. The nominal concentration of the Mn atoms in the investigated samples was 6% and 8%. We do not observe changes in the electronic structure of Ca and As introduced by the presence of the Mn atoms. We find, in contrast, considerable changes in the electronic structure around the Mn atoms. Moreover, for the first time it was possible to indicate the preferred interstitial positions of the Mn atoms.
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