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Institution

Johannes Kepler University of Linz

EducationLinz, Oberösterreich, Austria
About: Johannes Kepler University of Linz is a education organization based out in Linz, Oberösterreich, Austria. It is known for research contribution in the topics: Thin film & Quantum dot. The organization has 6605 authors who have published 19243 publications receiving 385667 citations.


Papers
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Journal ArticleDOI
TL;DR: An up to now unmatched structural perfection of the quantum dot crystal and a narrow quantum dot size distribution are revealed, indicating a low defect density in the three-dimensional SiGe quantum dot crystals.
Abstract: Modern nanotechnology offers routes to create new artificial materials, widening the functionality of devices in physics, chemistry, and biology. Templated self-organization has been recognized as a possible route to achieve exact positioning of quantum dots to create quantum dot arrays, molecules, and crystals. Here we employ extreme ultraviolet interference lithography (EUV-IL) at a wavelength of I ) 13.5 nm for fast, large-area exposure of templates with perfect periodicity. Si(001) substrates have been patterned with two-dimensional hole arrays using EUV-IL and reactive ion etching. On these substrates, three-dimensionally ordered SiGe quantum dot crystals with the so far smallest quantum dot sizes and periods both in lateral and vertical directions have been grown by molecular beam epitaxy. X-ray diffractometry from a sample volume corresponding to about 3.6 × 107 dots and atomic force microscopy (AFM) reveal an up to now unmatched structural perfection of the quantum dot crystal and a narrow quantum dot size distribution. Intense interband photoluminescence has been observed up to room temperature, indicating a low defect density in the three-dimensional (3D) SiGe quantum dot crystals. Using the Ge concentration and dot shapes determined by X-ray and AFM measurements as input parameters for 3D band structure calculations, an excellent quantitative agreement between measured and calculated PL energies is obtained. The calculations show that the band structure of the 3D ordered quantum dot crystal is significantly modified by the artificial periodicity. A calculation of the variation of the eigenenergies based on the statistical variation in the dot dimensions as determined experimentally ( ±10% in linear dimensions) shows that the calculated electronic coupling between neighboring dots is not destroyed due to the quantum dot size variations. Thus, not only from a structural point of view but also with respect to the band structure, the 3D ordered quantum dots can be regarded as artificial crystal.

157 citations

Journal ArticleDOI
TL;DR: It is shown that this phenomenon is based on geometric principles, namely on a periodic pattern of interconnected half-open capillary channels that narrow and widen, and derived a theoretical model for the local behaviour of the liquid in such capillaries.
Abstract: Moisture-harvesting lizards such as the Texas horned lizard (Iguanidae: Phrynosoma cornutum) live in arid regions. Special skin adaptations enable them to access water sources such as moist sand and dew: their skin is capable of collecting and transporting water directionally by means of a capillary system between the scales. This fluid transport is passive, i.e. requires no external energy, and directs water preferentially towards the lizard's snout. We show that this phenomenon is based on geometric principles, namely on a periodic pattern of interconnected half-open capillary channels that narrow and widen. Following a biomimetic approach, we used these principles to develop a technical prototype design. Building upon the Young-Laplace equation, we derived a theoretical model for the local behaviour of the liquid in such capillaries. We present a global model for the penetration velocity validated by experimental data. Artificial surfaces designed in accordance with this model prevent liquid flow in one direction while sustaining it in the other. Such passive directional liquid transport could lead to process improvements and reduction of resources in many technical applications.

157 citations

Journal ArticleDOI
TL;DR: In this article, it is shown how self-organized structures can be applied in the development of actuators with complex, out-of-plane actuationmodes, which is then demonstrated in the case of dielectric elastomer actuators.
Abstract: When a stretched elastomer is laminated to a flat plastic frame, a complex shape is formed, which is termed a minimum-energy structure. It is shown how self-organized structures can be applied in the development of actuators with complex, out-of-plane actuationmodes. This unusual concept is then demonstrated in the case of dielectric elastomer actuators. Among advantages of this approach are the simplicity in manufacturing, the potential complexity and sophistication of the manufactured structures, and the general benefits of the concept when applied to other electro-mechanically active materials.

157 citations

Journal ArticleDOI
TL;DR: In this article, a class of a posteriori parameter choice strategies for Tikhonov regularization (including variants of Morozov's and Arcangeli's methods) were proposed, leading to optimal convergence rates toward the minimal-norm, least-squares solution of an ill-posed linear operator equation in the presence of noisy data.
Abstract: We propose a class ofa posteriori parameter choice strategies for Tikhonov regularization (including variants of Morozov's and Arcangeli's methods) that lead to optimal convergence rates toward the minimal-norm, least-squares solution of an ill-posed linear operator equation in the presence of noisy data.

154 citations

Journal ArticleDOI
TL;DR: The fabrication of pure and stable hexagonal silicon evidenced by structural characterization is demonstrated, which opens the way for exploring its optical, electrical, superconducting, and mechanical properties.
Abstract: Silicon, arguably the most important technological semiconductor, is predicted to exhibit a range of new and interesting properties when grown in the hexagonal crystal structure. To obtain pure hexagonal silicon is a great challenge because it naturally crystallizes in the cubic structure. Here, we demonstrate the fabrication of pure and stable hexagonal silicon evidenced by structural characterization. In our approach, we transfer the hexagonal crystal structure from a template hexagonal gallium phosphide nanowire to an epitaxially grown silicon shell, such that hexagonal silicon is formed. The typical ABABAB... stacking of the hexagonal structure is shown by aberration-corrected imaging in transmission electron microscopy. In addition, X-ray diffraction measurements show the high crystalline purity of the material. We show that this material is stable up to 9 GPa pressure. With this development, we open the way for exploring its optical, electrical, superconducting, and mechanical properties.

154 citations


Authors

Showing all 6718 results

NameH-indexPapersCitations
Wolfgang Wagner1562342123391
A. Paul Alivisatos146470101741
Klaus-Robert Müller12976479391
Christoph J. Brabec12089668188
Andreas Heinz108107845002
Niyazi Serdar Sariciftci9959154055
Lars Samuelson9685036931
Peter J. Oefner9034830729
Dmitri V. Talapin9030339572
Tomás Torres8862528223
Ramesh Raskar8667030675
Siegfried Bauer8442226759
Alexander Eychmüller8244423688
Friedrich Schneider8255427383
Maksym V. Kovalenko8136034805
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
20242
202354
2022187
20211,404
20201,412
20191,365