Refine
Year of publication
Document Type
Way of publication
- Open Access (2)
Keywords
Institute
- FG Geopedologie und Landschaftsentwicklung (16)
- FG Technische Akustik (16)
- FG Halbleitermaterialien (10)
- FG Angewandte Physik und Halbleiterspektroskopie (5)
- FG Bodenschutz und Rekultivierung (2)
- FG Ökologie (2)
- Forschungszentrum Landschaftsentwicklung und Bergbaulandschaften (FZLB) (2)
- Zentrale Analytik der BTU Cottbus-Senftenberg (ZA-BTU) / Zentrales Analytisches Labor (2)
- FG Anorganische Chemie (1)
- FG Biotechnologie der Wasseraufbereitung (1)
Defects play an important role for surface reconstructions and therefore also influence the substrate growth. In this work we present a first principle calculation for the Ge(001) surface without and with tin impurities incorporated into the top surface layer. By mapping the system onto an Ising-type model, with interaction constants taken from density functional theory, the stability of the surface reconstructions under the influence of different concentrations of tin impurities is explored. This approach allows us to simulate the possible phase transitions for the different surface reconstructions including the local structure around the tin impurity atoms. In addition, we compare our theoretical results with experimental STM images on clean and Sn-doped Ge(100) surfaces.
Slope deposits, which veil entire slopes or large parts of them in a rather uniform manner (cover beds), are ubiquitous in the subdued mountains of Central Europe. Here we provide an overview of the current state of knowledge on these deposits. The Central European cover beds are divided into (1) the upper layer that is ubiquitously distributed and displays a relatively constant thickness; (2) the intermediate layer the distribution of which is mainly restricted to flat relief, to slope depressions, and to lee-ward facing slopes; and (3) the basal layer, which is rather widespread again. Both the upper and intermediate layer contain intermixed loess, whereas the basal layer is free of loess and typically has a high bulk density. Aside from the loess content, the composition of the layers differs, reflecting varying portions of crushed and chemically weathered rock allocated from up-slope. This causes notable diversity depending on bedrock and, thus, induces remarkable regional differences.
Cover beds were mainly formed by periglacial gelifluction. The upper layer formed in the Late Glacial possibly during several short episodes of activity. In contrast, the underlying layers may be diachronous; nevertheless, they display recurring vertical sequences. This is probably due to the fact that loess-free layers usually could not deposit as long as there was loess in the environs, which may have been inherited from older deposits. Thus, the last phase of surface wash, during which older loess was removed, determines the age of the lower layers.