@misc{LangeErnstTeubneretal., author = {Lange, Felix and Ernst, Owen C. and Teubner, Thomas and Richter, Carsten and Schmidbauer, Martin and Skibitzki, Oliver and Schroeder, Thomas and Schmidt, Peer and Boeck, Torsten}, title = {In-plane growth of germanium nanowires on nanostructured Si(001)/SiO2 substrates}, series = {Nano Futures}, volume = {4}, journal = {Nano Futures}, number = {3}, issn = {2399-1984}, doi = {10.1088/2399-1984/ab82a0}, pages = {1 -- 8}, abstract = {Germanium (Ge) nanowires (NWs) were grown in-plane on nano-structured Si(001)/SiO2 substrates by molecular beam epitaxy using gold (Au) as the solvent. The site-selective NW growth was enabled by a rectangular array of gold droplets on silicon (Si) tips with an Au nuclei density below 0.25 μm-2 on the surrounding silicon oxide (SiO2). The initial growth of Ge NWs starting from Si-Au droplets with SixGe1-x nucleation from ternary alloy is discussed from a thermodynamic point of view. The in-plane NW elongation occurred within ⟨110⟩ directions on the substrate and NWs were mainly bounded by two 55◦ inclined 111 facets and a less pronounced planar (001) top facet. Fully relaxed crystal lattices of Ge NWs were observed from two-dimensional reciprocal space maps of x-ray diffraction measurements.}, language = {en} } @misc{SchmidtBussEwertetal., author = {Schmidt, Thomas and Buß, Lars and Ewert, Moritz and Sch{\"o}nhoff, Gunnar and Wehling, Tim Oliver and Falta, Jens}, title = {Adsorption of sulfur on Si(111)}, series = {Surface Science}, volume = {694}, journal = {Surface Science}, issn = {0039-6028}, doi = {10.1016/j.susc.2019.121561}, pages = {11}, abstract = {The adsorption of S on Si(111)- 7 × 7 has been investigated for different preparation schemes and parameters. S was supplied from an electrochemical Ag2S cell. For room temperature adsorption and subsequent annealing, no ordered S induced reconstruction can be observed with spot profile analysis low-energy electron diffraction (SPALEED). S deposition at temperatures above about 400°C, however, leads to a well-ordered reconstruction. Judging from the LEED pattern, the same reconstruction was already observed by Metzner et al. [Surf. Sci. 377-379(1997) 71-74] who identified it as 4 × 4 reconstruction. The upper temperature limit for the pre-paration of this superstructure depends on S flux, which is needed to compensate for desorption. Prolonged S exposure leads to surface roughening, as observed with SPALEED and scanning tunneling microscopy (STM), pointing to surface etching by S. From our SPALEED data, we can conclude that the observed reconstruction is not a 4 × 4 reconstruction, but a 20/12 superstructure with a rectangular unit cell that exists in three rotational domains, as confirmed by STM. Different structural trial models have been assessed with density functional theory. Among these model structures, a configuration with dimers adsorbed on bridging sites, with a S coverage of 1 monolayer, is most likely, since it is energetically favorable and is in agreement with all experimental results.}, language = {en} } @misc{KrisponeitFischerEsseretal., author = {Krisponeit, Jon-Olaf and Fischer, Simon and Esser, Sven and Moshnyaga, Vasily and Schmidt, Thomas and Piper, Louis F. J. and Flege, Jan Ingo and Falta, Jens}, title = {The morphology of VO2/TiO2(001): terraces, facets, and cracks}, series = {Scientific Reports}, volume = {10}, journal = {Scientific Reports}, issn = {2045-2322}, doi = {10.1038/s41598-020-78584-9}, pages = {8}, abstract = {Vanadium dioxide (VO2) features a pronounced, thermally-driven metal-to-insulator transition at 340 K. Employing epitaxial stress on rutile TiO2(001) substrates, the transition can be tuned to occur close to room temperature. Striving for applications in oxide-electronic devices, the lateral homogeneity of such samples must be considered as an important prerequisite for efforts towards miniaturization. Moreover, the preparation of smooth surfaces is crucial for vertically stacked devices and, hence, the design of functional interfaces. Here, the surface morphology of VO2/TiO2(001) films was analyzed by low-energy electron microscopy and diffraction as well as scanning probe microscopy. The formation of large terraces could be achieved under temperature-induced annealing, but also the occurrence of facets was observed and characterized. Further, we report on quasi-periodic arrangements of crack defects which evolve due to thermal stress under cooling. While these might impair some applicational endeavours, they may also present crystallographically well-oriented nano-templates of bulk-like properties for advanced approaches.}, language = {en} }