Wolfgang Theis

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Crystallography, the primary method for determining the 3D atomic positions in crystals, has been fundamental to the development of many fields of science. However, the atomic positions obtained from crystallography represent a global average of many unit cells in a crystal. Here, we report, for the first time, the determination of the 3D coordinates of(More)
Single element quasicrystalline monolayers were prepared by deposition of antimony and bismuth on the fivefold surface of icosahedral Al71.5Pd21Mn8.5 and the tenfold surface of decagonal Al71.8Ni14.8Co13.4. Elastic helium atom scattering and low energy electron diffraction of the monolayers show Bragg peaks at the bulk derived positions of the clean(More)
The precise calibration of thermally driven processes in scanning tunnelling microscope (STM) manipulation experiments, especially at room temperature and above, is necessary to uncover an accurate picture of non-thermal dynamical processes such as desorption induced by electronic transitions, driven by the STM current. Here we probe the displacement (the(More)
The BTA deep hole drilling method was developed for machining holes with a high length-to-diameter ratio, good surface finish and straightness. The dynamic properties of the slender tool-boring bar combination necessary for producing this type of geometry significantly influence the overall process dynamics and lead to characteristic disturbances. These(More)
Perfect crystals are rare in nature. Real materials often contain crystal defects and chemical order/disorder such as grain boundaries, dislocations, interfaces, surface reconstructions and point defects. Such disruption in periodicity strongly affects material properties and functionality. Despite rapid development of quantitative material characterization(More)
Epitaxial interfaces of commensurate periodic materials can be characterized by a locking into registry of their atomic structure. This characteristic is identified as a natural framework to capture the essence of epitaxy also for systems including quasicrystalline materials. The resulting general definition for epitaxy requires a matching of reciprocal(More)
The surfaces of quasicrystals have been extensively studied since about 1990. In this paper we review work on the structure and morphology of clean surfaces, and their electronic and phonon structure. We also describe progress in adsorption and epitaxy studies. The paper is illustrated throughout with examples from the literature. We offer some reflections(More)
At a hydrogen coverage of one monolayer, W(110) is known to exhibit a Fermi nesting in its electronic surface states with a nesting vector q{N} of 0.9 A{-1} along [001]. Here we show that additional H adsorption allows a controlled tuning of q{N}. As q{N} approaches the commensurate value of 1.0 A{-1}, its signature in inelastic He-atom scattering becomes(More)
Similar p h e n o m e n a were also obse rved for t he case of ~ , /3-naphthols and m, f l -naph thy lamines h y d r o g e n b o n d e d wi th pyridil le. Th i s t y p e of f luorescence q u e n c h i n g caused b y t he ac id-base in te rac t ion be tween ~-e lec t ron s y s t e m s v ia t he h y d rogen b o n d m a y h a v e i ts ana l ogy in t he so lven(More)
Electron tomography in materials science has flourished with the demand to characterize nanoscale materials in three dimensions (3D). Access to experimental data is vital for developing and validating reconstruction methods that improve resolution and reduce radiation dose requirements. This work presents five high-quality scanning transmission electron(More)