@misc{KersteinSchmidtNedelecetal., author = {Kerstein, Alan R. and Schmidt, Heiko and N{\´e}d{\´e}lec, Renaud and Wunsch, Scott and Sayler, Ben J.}, title = {Analysis and numerical simulation of a laboratory analog of radiatively induced cloud-top entrainment}, series = {Bulletin of the American Physical Society Dynamics}, volume = {55}, journal = {Bulletin of the American Physical Society Dynamics}, number = {16}, language = {en} } @misc{MuellerSchwarzSchmidtetal., author = {M{\"u}ller, Carola J. and Schwarz, Ulrich and Schmidt, Peer and Schnelle, Walter and Doert, Thomas}, title = {High-Pressure Synthesis, Crystal Structure, and Properties of GdS2 with Thermodynamic Investigations in the Phase Diagram Gd-S,}, series = {Zeitschrift f{\"u}r anorganische und allgemeine Chemie}, volume = {636}, journal = {Zeitschrift f{\"u}r anorganische und allgemeine Chemie}, number = {6}, issn = {1521-3749}, doi = {10.1002/zaac.201000015}, pages = {947 -- 953}, abstract = {Gadolinium disulfide was prepared by high-pressure synthesis at 8 GPa and 1173 K. It crystallizes in the monoclinic space group P121/a1 (No. 14) with lattice parameters a = 7.879(1) {\AA}; b = 3.936(1) {\AA}, c = 7.926(1) {\AA} and β = 90.08(1)°. The crystal structure is a twofold superstructure of the aristotype ZrSSi and consists of puckered cationic [GdS]+ double slabs that are sandwiched by planar sulfur sheets containing S22- dumbbells. The thermal decomposition of GdS2 proceeds via the sulfur-deficient polysulfides GdS1.9, GdS1.85 and GdS1.77 and eventually results in the sesquisulfide Gd2S3. GdS2 is a paramagnetic semiconductor which orders antiferromagnetically at TN = 7.7(1) K. A metamagnetic transition is observed in the magnetically ordered state.}, language = {en} } @inproceedings{BlehOstendorfMertenetal., author = {Bleh, D. and Ostendorf, Ralf and Merten, A. and Grahmann, Jan and Schenk, Harald and Kunzer, M. and Schmidt, R. and Wagner, J.}, title = {Miniaturization of a fast tunable external cavity QCL with customized gratings and MOEMS components}, series = {International Quantum Cascade Lasers School \& Workshop (IQCLSW), Policoro, Italy}, booktitle = {International Quantum Cascade Lasers School \& Workshop (IQCLSW), Policoro, Italy}, pages = {1 -- 2}, language = {en} } @misc{GrzelaCapelliniKoczorowskietal., author = {Grzela, Tomasz and Capellini, Giovanni and Koczorowski, Wojciech and Schubert, Markus Andreas and Czajka, Ryszard and Curson, Neil J. and Heidmann, Inga and Schmidt, Thomas and Falta, Jens and Schr{\"o}der, Thomas}, title = {Growth and evolution of nickel - germanide nanonstructures on Ge(001)}, series = {Nanotechnology}, volume = {26}, journal = {Nanotechnology}, number = {38}, issn = {1361-6528}, pages = {385701}, 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} } @misc{PozarowskaPleinesPrietoetal., author = {Pozarowska, Emilia and Pleines, Linus and Prieto, Mauricio J. and Tănase, Liviu Christian and Souza Caldas, Lucas de and Tiwari, Aarti and Schmidt, Thomas and Falta, Jens and Morales, Carlos and Flege, Jan Ingo}, title = {The relation between structure sensitivity and doping of ceria(111) vs. ceria(100)}, series = {Verhandlungen der DPG}, journal = {Verhandlungen der DPG}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, abstract = {CeOx-Cu inverse catalysts have been shown to convert CO2 into valuable chemicals through catalytic hydrogenation. The catalytic activity may further be enhanced by alloying ceria with trivalent, catalytically active metals, such as Sm, promoting the formation of Ce3+ active sites. In this work, the structural and chemical properties of (111)- and (100)- oriented CeOx islands alloyed with samarium were explored by low-energy electron microscopy and X-ray photoemission electron microscopy. After Sm deposition on the as-grown CeOx islands, the near-surface region of (100)-oriented CeOx is reduced after exposure to H2 at 470 ∘C, whereas the deeper layers as well as the whole (111)-oriented islands retain the Ce4+ state. Subsequent reoxidation with O2 leads to the complete Ce4+ state recovery, suggesting the healing of oxygen vacancies. Additional annealing at 470 ∘C induces samarium diffusion into the ceria matrix. Yet, subsequent exposure to H2 reduces neither the (111)- nor the (100)-oriented CeSmOx islands, suggesting a quite unexpected stability of this system.}, language = {en} } @misc{PożarowskaPleinesEwertetal., author = {Pożarowska, Emilia and Pleines, Linus and Ewert, Moritz and Prieto, Mauricio J. and Tănase, Liviu Christian and Souza Caldas, Lucas de and Tiwari, Aarti and Schmidt, Thomas and Falta, Jens and Krasovskii, Eugene and Morales, Carlos and Flege, Jan Ingo}, title = {Preparation and stability of the hexagonal phase of samarium oxide on Ru(0001)}, series = {Ultramicroscopy}, volume = {250}, journal = {Ultramicroscopy}, issn = {0304-3991}, doi = {10.1016/j.ultramic.2023.113755}, abstract = {We have used low-energy electron microscopy (LEEM), micro-illumination low-energy electron diffraction (µLEED) supported by ab initio calculations, and X-ray absorption spectroscopy (XAS) to investigate in-situ and in real-time the structural properties of Sm2O3 deposits grown on Ru(0001), a rare-earth metal oxide model catalyst. Our results show that samarium oxide grows in a hexagonal A-Sm2O3 phase on Ru(0001), exhibiting a (0001) oriented-top facet and (113) side facets. Upon annealing, a structural transition from the hexagonal to cubic phase occurs, in which the Sm cations exhibit the +3 oxidation state. The unexpected initial growth in the A-Sm2O3 hexagonal phase and its gradual transition to a mixture with cubic C-Sm2O3 showcases the complexity of the system and the critical role of the substrate in the stabilization of the hexagonal phase, which was previously reported only at high pressures and temperatures for bulk samaria. Besides, these results highlight the potential interactions that Sm could have with other catalytic compounds with respect to the here gathered insights on the preparation conditions and the specific compounds with which it interacts.}, language = {en} } @misc{TschammerBussPożarowskaetal., author = {Tschammer, Rudi and Buß, Lars and Pożarowska, Emilia and Morales, Carlos and Senanayake, Sanjaya D. and Prieto, Mauricio J. and Tănase, Liviu C. and de Souza Caldas, Lucas and Tiwari, Aarti and Schmidt, Thomas and Ni{\~n}o, Miguel A. and Foerster, Michael and Falta, Jens and Flege, Jan Ingo}, title = {High-temperature growth of CeOx on Au(111) and behavior under reducing and oxidizing conditions}, series = {The journal of physical chemistry C}, volume = {129}, journal = {The journal of physical chemistry C}, number = {7}, publisher = {American Chemical Society (ACS)}, address = {Washington, DC}, issn = {1932-7447}, doi = {10.1021/acs.jpcc.4c08072}, pages = {3583 -- 3594}, abstract = {Inverse oxide-metal model catalysts can show superior activity and selectivity compared with the traditional supported metal-oxide architecture, commonly attributed to the synergistic overlayer-support interaction. We have investigated the growth and redox properties of ceria nanoislands grown on Au(111) between 700 and 890 °C, which yields the CeO2-Au(111) model catalyst system. We have observed a distinct correlation between deposition temperature, structural order, and oxide composition through low-energy electron microscopy, low-energy electron diffraction, intensity-voltage curves, and X-ray absorption spectroscopy. Improved structural order and thermal stability of the oxide have been achieved by increasing the oxygen chemical potential at the substrate surface using reactive oxygen (O/O2) instead of molecular O2 during growth. In situ characterization under reducing (H2) and oxidizing atmospheres (O2, CO2) indicates an irreversible loss of structural order and redox activity at high reduction temperatures, while moderate temperatures result in partial decomposition of the ceria nanoislands (Ce3+/Ce4+) to metallic cerium (Ce0). The weak interaction between Au(111) and CeOx would facilitate its reduction to the Ce0 metallic state, especially considering the comparatively strong interaction between Ce0 and Au0. Besides, the higher reactivity of atomic oxygen promotes a stronger interaction between the gold and oxide islands during the nucleation process, explaining the improved stability. Thus, we propose that by driving the nucleation and growth of the ceria/Au system in a highly oxidizing regime, novel chemical properties can be obtained.}, language = {en} } @misc{SchmidtSkerencakFrechPanaketal., author = {Schmidt, Moritz and Skerencak-Frech, Andrej and Panak, Petra J. and Huittinen, Nina}, title = {Curium(III) luminescence spectroscopy as a tool for species determination}, series = {Chemical Society reviews}, journal = {Chemical Society reviews}, publisher = {Royal Society of Chemistry}, address = {London}, doi = {10.1039/d5cs00764j}, pages = {60}, abstract = {Curium is an artificial transuranic element with atomic number 96. It is typically found in its +III oxidation state, which is stabilized by a 5f7 electron configuration. CmIII exhibits intense lumi-nescence from its first excited 6D'7/2 to its 8S'7/2 ground state in the red part of the visual spec-trum. Due to the nature of the 5f electron shell, this luminescence is sensitive to changes in the chemical environment of the CmIII probe, while being detectable in the trace concentration range. This unique combination has established CmIII luminescence spectroscopy as an ideal tool for speciation studies in complex systems, particularly those relevant to the nuclear fuel cycle. In this review, we present an overview of the developments and applications of CmIII lumines-cence spectroscopy in the last 20 years since the last comprehensive review was published. The discussed studies have been categorized according to their chemical environment into reactions at the water/mineral interface, studies of solids containing CmIII, aqueous complexation studies, spectroscopy in non-aqueous systems, and interaction of CmIII with biomolecules and biota. These systems correlate in large parts with areas of application in nuclear waste disposal sci-ence, separation processes within current and proposed nuclear fuel cycles, and radioecological research. We summarize the most important findings in the studies, identify emerging trends and persistent challenges in the field of CmIII luminescence spectroscopy. Finally, we offer an outlook on potential future developments and research directions in this area.}, language = {en} } @misc{PożarowskaPleinesPrietoetal., author = {Pożarowska, Emilia and Pleines, Linus and Prieto, Mauricio J. and Tănase, Liviu C. and de Souza Caldas, Lucas and Tiwari, Aarti and Schmidt, Thomas and Falta, Jens and Morales, Carlos and Flege, Jan Ingo}, title = {The relationship between Sm alloying and structure sensitivity of ceria(111)- and (100)-oriented nanoislands on Cu(111)}, series = {Physical chemistry, chemical physics}, volume = {27}, journal = {Physical chemistry, chemical physics}, number = {29}, publisher = {Royal Society of Chemistry (RSC)}, address = {Cambridge}, issn = {1463-9076}, doi = {10.1039/D5CP01171J}, pages = {15691 -- 15703}, abstract = {We have investigated the complex dynamics of samarium deposition on ceria islands of different orientations, namely (111) and (100), grown side by side on a Cu(111) single-crystal substrate, followed by post-oxidation and annealing under ultra-high vacuum conditions. Only the (100)-oriented ceria islands undergo substantial initial reduction upon samarium deposition at 740 K via a pathway similar to the strong Ce-ceria interfacial interaction, while the (111)-oriented islands remain in the Ce4+ oxidation state. This remarkable structure sensitivity is explained by the different energies required for oxygen vacancy formation for both oxide orientations. Subsequent mild re-oxidation with O2 results in the complete recovery of the Ce4+ oxidation state in the (100)-oriented islands, indicating the complete healing of oxygen vacancies. In contrast, extended annealing at moderate temperatures likely induces persistent samarium incorporation into the cerium oxide matrix. Our results provide new insights into the complex structure-activity relationships in mixed rare-earth metal oxide systems and have promising implications for optimizing catalytic reactions over such compounds in reducing environments.}, language = {en} }