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- Özçetin, Seda
(creator_code:cre_t, designer, utgivare, creator_code:fmk_t, producent, creator_code:res_t, bilagor, fotograf, creator_code:vdg_t)
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Look, a ToSsphere! : Behind the checkbox of Terms of Service
- 2023
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Konstnärligt arbeteabstract
- In this project, I attempt to go behind the checkbox and unpack what is it that we agree on when we check ‘I have read and agree on ToS’ boxes. By engaging with ToS at different scales – zooming in and out – through reading, translating, and transposing, I explore what each mode of engagement reveals, what questions they lead to, and how these explorations could inform designers.
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| 2. |
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| 3. |
- Bhandary, Sumanta, 1985-, et al.
(författare)
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Correlated electron behavior of metalorganic molecules: insights from density functional theory and exact diagonalization studies.
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The proper description of electronic structure of correlated orbitals in the metal centers of functional metalorganics is a challenging problem. In this letter, we apply density functional theory and exact diagonalization method in a many body approach to study the ground state electronic conguration of iron porphyrin (FeP) molecule. Our study reveals that FeP is a potential candidate for realizing a spin crossover due to a subtle balance of crystal elds and hybridization of the Fe d-orbitals and ligand N p-states. Moreover, the mechanism of switching between two close lying electronic congurations of Fe-d orbitals is revealed. This hybrid method can generally be applied to properly describe the electronic and related low energy physics of the whole class of correlated metal centered organometallic molecules.
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| 4. |
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| 5. |
- Zholud, Dmitrii, 1984
(författare)
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Tail approximations for the Student t-, F-, and Welch statistics for non-normal and not necessarily i.i.d. random variables
- 2014
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Ingår i: Bernoulli. - : Bernoulli Society for Mathematical Statistics and Probability. - 1350-7265. ; 20:4, s. 2102-2130
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Tidskriftsartikel (refereegranskat)abstract
- Let T be the Student one- or two-sample t-, F-, or Welch statistic. Now release the underlying assumptions of normality, independence and identical distribution and consider a more general case where one only assumes that the vector of data has a continuous joint density. We determine asymptotic expressions for P(T > u) as u -> infinity for this case. The approximations are particularly accurate for small sample sizes and may be used, for example, in the analysis of High-Throughput Screening experiments, where the number of replicates can be as low as two to five and often extreme significance levels are used. We give numerous examples and complement our results by an investigation of the convergence speed - both theoretically, by deriving exact bounds for absolute and relative errors, and by means of a simulation study.
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| 6. |
- Benter, Sandra
(författare)
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Adventures of III-V Semiconductor Surfaces
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Tailoring the surface composition and morphology of materials to enable new electronic devices is important for a wide range of applications such as quantum computing or spintronics. A fundamental understanding of the changes induced in the surface during different process steps can help to establish new synthesis routes as well as devices. This thesis focuses on the manipulation of III-V semiconductor compounds, in particularthe surfaces of InAs and GaAs crystals.By implementing lithographically defined metal islands on the InAs surface, we push the boundaries of substrate annealing temperatures inhibiting the formation of In droplets locally. The employed Pd layer acts as a sink for freely diffusing In atoms above the congruent melting temperature. Here, As atoms go into gas phase at a higher rate compared to In due to the difference in vapor pressure. This lateral control over the concentration of In on the surface was investigated via scanning electron, atomic force as well as X-ray photoemission electron microscopy (XPEEM), and opens new pathways for epitaxy and the synthesis of heterostructures. Furthermore, theoretical studies have shown that the implementation of Bi atoms into the lattice of III-V compound semiconductors can facilitate band gap reduction and increased spin-orbit coupling desirable for fabricating of topological insulators. Particularly, the interaction of group III elements with Bi has attracted great interest. However, manufacturing these diluted Bismides is not trivial, since most approaches like molecular beam epitaxy, synthesis from the melt or metal organic vapor deposition suffer from limited and inhomogeneous Bi incorporation into the crystal.By following the approach of depositing Bi atoms onto a III-V sample and subsequent annealing, this thesis aims to synthesize and characterize heterostructures displaying III-V bulk properties and a surface made of III-As-Bi compounds. Different sample preparation routes were explored focusing on GaAs and InAs substrates with zinc blende (ZB) and wurtzite (WZ) crystal structure. The latter is only achievable in low-dimensional materials and will be employed in the form of InAs nanosheets. Part of this study focusses on the investigation of Bi-induced structural and chemical changes in the surface of the III-V compounds by utilizing surface sensitive techniques such as scanning tunneling microscopy, X-ray photoemission spectroscopy, low energy electron diffraction and XPEEM. Our results show that the mechanism of Bi incorporation is highly dependent on the underlying crystal structure, as well as process parameters such as time and substrate temperature. Additionally, first band structure measurements of InAs WZ crystal nanosheets collected via averaging angleresolved photoemission spectroscopy (ARPES) are presented. In contrast to other ZB crystal facets, a 2D electron gas (2DEG) is already detected after removing the native oxide and diminished after Bi deposition. We attribute the origin of the 2DEG to unique step and edge morphologies found on the WZ nanosheets. The thesis concludes with an ARPES study on InAs(111)B substrates presenting new electronic states inside the band gap based on the interaction of Bi and As atoms.
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| 7. |
- Di Bernardo, Mario, et al.
(författare)
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Contraction analysis for a class of nondifferentiable systems with applications to stability and network synchronization
- 2014
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Ingår i: SIAM Journal of Control and Optimization. - : Society for Industrial & Applied Mathematics (SIAM). - 0363-0129 .- 1095-7138. ; 52:5, s. 3203-3227
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we extend to a generic class of piecewise smooth dynamical systems a fundamental tool for the analysis of convergence of smooth dynamical systems: contraction theory. We focus on switched nondifferentiable systems satisfying Caratheodory conditions for the existence and uniqueness of a solution. After generalizing the classical definition of contraction to this class of dynamical systems, we give sufficient conditions for global convergence of their trajectories. The theoretical results are then applied to solve a set of representative problems such as proving global asymptotic stability of switched linear systems, giving conditions for incremental stability of piecewise smooth systems, and analyzing the convergence of networked switched systems.
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| 8. |
- Zhong, Haiyi, et al.
(författare)
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Gas storage in geological formations : A comparative review on carbon dioxide and hydrogen storage
- 2024
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Ingår i: Materials Today Sustainability. - : Elsevier BV. - 2589-2347. ; 26
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Tidskriftsartikel (refereegranskat)abstract
- Carbon dioxide and hydrogen storage in geological formations at Gt scale are two promising strategies toward net-zero carbon emissions. To date, investigations into underground hydrogen storage (UHS) remain relatively limited in comparison to the more established knowledge body of underground carbon dioxide storage (UCS). Despite their analogous physical processes can be used for accelerating the advancements in UHS technology, the existing distinctions possibly may hinder direct applicability. This review therefore contributes to advancing our fundamental understanding on the key differences between UCS and UHS through multi-scale comparisons. These comparisons encompass key factors influencing underground gas storage, including storage media, trapping mechanisms, respective fluid properties, petrophysical properties, and injection scenarios. They provide guidance for the conversion of our existing knowledge from UCS to UHS, emphasizing the necessity of incorporating these factors relevant to their trapping and loss mechanisms. The article also outlines future directions to address the crucial knowledge gaps identified, aiming to enhance the utilisation of geological formations for hydrogen and carbon dioxide storage.
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| 9. |
- Benter, Sandra, et al.
(författare)
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Geometric control of diffusing elements on InAs semiconductor surfaces via metal contacts
- 2023
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Ingår i: Nature Communications. - 2041-1723. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Local geometric control of basic synthesis parameters, such as elemental composition, is important for bottom-up synthesis and top-down device definition on-chip but remains a significant challenge. Here, we propose to use lithographically defined metal stacks for regulating the surface concentrations of freely diffusing synthesis elements on compound semiconductors. This is demonstrated by geometric control of Indium droplet formation on Indium Arsenide surfaces, an important consequence of incongruent evaporation. Lithographic defined Aluminium/Palladium metal patterns induce well-defined droplet-free zones during annealing up to 600 °C, while the metal patterns retain their lateral geometry. Compositional and structural analysis is performed, as well as theoretical modelling. The Pd acts as a sink for free In atoms, lowering their surface concentration locally and inhibiting droplet formation. Al acts as a diffusion barrier altering Pd’s efficiency. The behaviour depends only on a few basic assumptions and should be applicable to lithography-epitaxial manufacturing processes of compound semiconductors in general.
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| 10. |
- Benter, S., et al.
(författare)
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Quasi One-Dimensional Metal-Semiconductor Heterostructures
- 2019
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 19:6, s. 3892-3897
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Tidskriftsartikel (refereegranskat)abstract
- The band offsets occurring at the abrupt heterointerfaces of suitable material combinations offer a powerful design tool for high performance or even new kinds of devices. Because of a large variety of applications for metal-semiconductor heterostructures and the promise of low-dimensional systems to present exceptional device characteristics, nanowire heterostructures gained particular interest over the past decade. However, compared to those achieved by mature two-dimensional processing techniques, quasi one-dimensional (1D) heterostructures often suffer from low interface and crystalline quality. For the GaAs-Au system, we demonstrate exemplarily a new approach to generate epitaxial and single crystalline metal-semiconductor nanowire heterostructures with atomically sharp interfaces using standard semiconductor processing techniques. Spatially resolved Raman measurements exclude any significant strain at the lattice mismatched metal-semiconductor heterojunction. On the basis of experimental results and simulation work, a novel self-assembled mechanism is demonstrated which yields one-step reconfiguration of a semiconductor-metal core-shell nanowire to a quasi 1D axially stacked heterostructure via flash lamp annealing. Transmission electron microscopy imaging and electrical characterization confirm the high interface quality resulting in the lowest Schottky barrier for the GaAs-Au system reported to date. Without limiting the generality, this novel approach will open up new opportunities in the syntheses of other metal-semiconductor nanowire heterostructures and thus facilitate the research of high-quality interfaces in metal-semiconductor nanocontacts.
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