@misc{GroenkeArroziBronkallaetal., author = {Gr{\"o}nke, Martin and Arrozi, Ubed S. F. and Bronkalla, Nadine and Schmidt, Peer and Valldor, Martin and Oswald, Steffen and Woodcock, Thomas G. and Eckert, Victoria and Hao, Qi and Pl{\"u}schke, Laura and Lederer, Albena and Nielsch, Kornelius and B{\"u}chner, Bernd and Kaskel, Stefan and Hampel, Silke}, title = {Layered α-TiCl₃: Microsheets on YSZ Substrates for Ethylene Polymerization with Enhanced Activity}, series = {Chemistry of Materials}, volume = {31}, journal = {Chemistry of Materials}, number = {14}, doi = {10.1021/acs.chemmater.9b01818}, pages = {5305 -- 5313}, abstract = {The transition metal halide α-titanium(III) chloride (α-TiCl₃) is a layered two-dimensional compound and a well-established Ziegler-Natta catalyst for the polymerization of ethylene. A new synthesis technique is used to obtain thin sheets of α-TiCl₃ that show exceptional physical properties in contrast to their bulk counterparts, due to an enlarged surface-to-volume ratio. Chemical vapor transport (CVT) of α-titanium(III) chloride directly on substrates results in microsheets that exhibit an improved catalytic effect. For rational planning of synthesis conditions, thermodynamic simulations of occurring gas-phase equilibria were performed. Based on these calculation results, crystal growth was achieved by adding GaCl₃via pure short term CVT in a temperature gradient of 700-600 K on yttrium-stabilized zirconia (YSZ) substrates. Phase pure, as-grown, single crystal sheets with high crystallinity and a thickness of around 4 μm were obtained. These thin sheets of α-TiCl₃ on YSZ substrates were implemented as catalysts for the ethylene polymerization reaction. A significant improvement of catalytic activity of 16\% was achieved, probably due to an increased surface-to-volume ratio. As a highlight, the as-grown microsheets were exfoliated subsequently to a thickness lower than 200 nm and an even higher catalytic activity of up to 24\% was confirmed experimentally due to delamination effects. This is the first time that an improved catalytic effect of α-TiCl₃ is observed as a result of downscaling from bulk to microsheets by CVT.}, language = {en} } @misc{GroenkeSchmidtValldoretal., author = {Gr{\"o}nke, Martin and Schmidt, Peer and Valldor, Martin and Oswald, Steffen and Wolf, Daniel and Lubk, Axel and B{\"u}chner, Bernd and Hampel, Silke}, title = {Chemical vapor growth and delamination of α-RuCl3 nanosheets down to the monolayer limit}, series = {Nanoscale}, volume = {10}, journal = {Nanoscale}, number = {40}, issn = {2040-3372}, doi = {10.1039/C8NR04667K}, pages = {19014 -- 19022}, abstract = {2D layered honeycomb magnet α-ruthenium(III) chloride (α-RuCl3) is a promising candidate to realize a Kitaev spin model. As alteration of physical properties on the nanoscale is additionally intended, new synthesis approaches to obtain phase pure α-RuCl3 nanocrystals have been audited. Thermodynamic simulations of occurring gas phase equilibria were performed and optimization of synthesis conditions was achieved based on calculation results. Crystal growth succeeded via chemical vapor transport (CVT) in a temperature gradient of 973 K to 773 K on YSZ substrates. Single crystal sheets of high crystallinity with heights ≤ 30 nm were obtained via pure CVT. The crystal properties were characterized by means of optical and electron microscopy, AFM, SAED, micro-Raman and XPS proving their composition, morphology, crystallinity and phase-purity. A highlight of our study is the successful individualization of nanocrystals and the delamination of nanosheets on YSZ substrates down to the monolayer limit (≤ 1 nm) which was realized by means of substrate exfoliation and ultrasonication in a very reproducible way.}, language = {en} } @misc{GroenkePohfleppSchmidtetal., author = {Gr{\"o}nke, Martin and Pohflepp, Danny and Schmidt, Peer and Valldor, Martin and Oswald, Steffen and Wolf, Daniel and Hao, Qi and Steiner, Udo and B{\"u}chner, Bernd and Hampel, Silke}, title = {Simulation and synthesis of alpha-MoCl₃ nanosheets on substrates by short time chemical vapor transport}, series = {Nano-Structures \& Nano-Objects}, journal = {Nano-Structures \& Nano-Objects}, number = {19}, issn = {2352-507X}, doi = {10.1016/j.nanoso.2019.100324}, pages = {1 -- 7}, abstract = {Alpha-molybdenum(III) chloride (MoCl₃) belongs to layered van-der-Waals materials, which are in focus to exhibit interesting properties due to their weak chemical and magnetic interactions. Especially the structure of alpha-MoCl₃ has been discussed in terms of symmetry breaking dimerization of Mo atoms at room temperature, which might led to exotic ground states. By exploiting the 2D materials characteristics, an investigation of physical properties on the nanoscale is intended. We herein demonstrate the probably first approach to synthesize phase pure, as-grown alpha-MoCl₃ few-layer nanosheets by means of a pure short time chemical vapor transport (CVT) process. Vapor growth benefits from a one-step deposition of high crystalline alpha-MoCl₃ nanosheets without stacking faults on a substrate. Thus, mostly applied subsequent delamination, associated with the introduction of structural defects, becomes redundant. According to the CVT process thermodynamic simulations of gas phase equilibria have been performed and the synthesis conditions could be optimized based on the calculation results. By CVT the as-grown nanolayers are deposited on sapphire (Al₂O₃) substrates by applying a temperature gradient of 70 K from 743 K to 673 K. Single crystalline sheets with thicknesses ≤75 nm down to five layer (3 nm) could be obtained by using a pure CVT process. According to the deposited nanostructures we approve the desired composition, morphology, phase purity and high crystallinity by using several microscopy and spectroscopy techniques. Furthermore, we show micro-RAMAN measurements which hint at a slight increase in phonon energies for nanosheets in comparison to the corresponding bulk phase.}, language = {en} } @misc{FroeschkeWolfHantuschetal., author = {Froeschke, Samuel and Wolf, Daniel and Hantusch, Martin and Giebeler, Lars and Wels, Martin and Gr{\"a}ßler, Nico and B{\"u}chner, Bernd and Schmidt, Peer and Hampel, Silke}, title = {Synthesis of micro- and nanosheets of CrCl3-RuCl3 solid solution by chemical vapour transport}, series = {Nanoscale}, volume = {29}, journal = {Nanoscale}, number = {14}, issn = {2040-3372}, doi = {10.1039/D2NR01366E}, pages = {10483 -- 10492}, abstract = {Solid solutions of 2D transition metal trihalides are rapidly growing in interest for the search for new 2D materials with novel properties at nanoscale dimensions. In this regard, we present a synthesis method for the Cr1-xRuxCl3 solid solution and describe the behaviour of the unit cell parameters over the whole composition range, which in general follows Vegard's law in the range of a = 5.958(6)CrCl3 … 5.9731(5)RuCl3 {\AA}, b = 10.3328(20)CrCl3 … 10.34606(21)RuCl3 {\AA}, c = 6.110(5)CrCl3 … 6.0385(5)RuCl3 {\AA} and β = 108.522(15)CrCl3 … 108.8314(14)RuCl3 °. The synthesized solid solution powder was subsequently used to deposit micro- and nanosheets directly on a substrate by applying chemical vapour transport in a temperature gradient of 575 °C → 525 °C for 2 h and 650 °C → 600 °C for 0.5 h as a bottom-up approach without the need for an external transport agent. The observed chromium chloride enrichment of the deposited crystals is predicted by thermodynamic simulation. The results allow for a nanostructure synthesis of this solid solution with a predictable composition down to about 30 nm in height and lateral size of several μm. When applying a quick consecutive delamination step, it is possible to obtain few- and monolayer structures, which could be used for further studies of downscaling effects for the CrCl3-RuCl3 solid solution. X-ray photoelectron spectroscopy, transmission electron microscopy and Raman spectroscopy were used to confirm the purity and quality of the synthesized crystals.}, language = {en} } @misc{GroenkeBuschbeckSchmidtetal., author = {Gr{\"o}nke, Martin and Buschbeck, Benjamin and Schmidt, Peer and Valldor, Martin and Oswald, Steffen and Hao, Qi and Lubk, Axel and Wolf, Daniel and Steiner, Udo and B{\"u}chner, Bernd and Hampel, Silke}, title = {Chromium Trihalides CrX₃(X = Cl, Br, I): Direct Deposition of Micro- and Nanosheets on Substrates by Chemical Vapor Transport}, series = {Advanced Materials Interfaces}, volume = {6}, journal = {Advanced Materials Interfaces}, number = {24}, issn = {2196-7350}, doi = {10.1002/admi.201901410}, pages = {11}, abstract = {The experimental observation of intrinsic ferromagnetism in single layered chromium trihalides CrX₃ (X = Cl, Br, I) has gained outstanding attention recently due to their possible implementation in spintronic devices. However, the reproducible preparation of highly crystalline chromium(III) halide nanolayers without stacking faults is still an experimental challenge. As chromium trihalides consist of adjacent layers with weak interlayer coupling, the preparation of ultrathin CrX₃ nanosheets directly on substrates via vapor transport proves as an advantageous synthesis technique. It is demonstrated that vapor growth of ultrathin highly crystalline CrX₃ micro- and nanosheets succeeds directly on yttrium stabilized zirconia substrates in a one-step process via chemical vapor transport (CVT) in temperature gradients of 100 K (600°C → 500°C for CrCl₃ and 650°C → 550°C for CrBr₃ or CrI₃) without a need for subsequent delamination. Due to simulation results, optimization of synthesis conditions is realized and phase pure CrX₃ nanosheets with thicknesses ≤25 nm are obtained via short term CVT. The nanosheets morphology, crystallinity, and phase purity are analyzed by several techniques, including microscopy, diffraction, and spectroscopy. Furthermore, a potential subsequent delamination technique is demonstrated to give fast access to CrX₃ monolayers using the example of CrCl₃ .}, language = {en} } @misc{MartinSuess, author = {Martin, Bernd and S{\"u}ß, Hendrik}, title = {Milnor algebras could be isomorphic to modular algebras}, language = {en} } @misc{MartinLavandoskyy, author = {Martin, Bernd and Lavandoskyy, Victor}, title = {A Symbolic Approach to Generation and Analysis of Finite Difference Schemes of Partial Differential Equations}, series = {arXiv.org : (math-ph)}, journal = {arXiv.org : (math-ph)}, pages = {24}, language = {en} } @misc{MartinHirsch, author = {Martin, Bernd and Hirsch, Tobias}, title = {Deformation with sections: Cotangent cohomology, flatnes conditions and modular germs}, series = {arXiv.org : (math.CV)}, journal = {arXiv.org : (math.CV)}, pages = {26}, language = {en} } @inproceedings{JantkeMemmelRostaninetal., author = {Jantke, Klaus-Peter and Memmel, Martin and Rostanin, Oleg and Thalheim, Bernhard and Tschiedel, Bernd}, title = {Decision Support by Learning-on-Demand}, series = {The 15th Conference on Advanced Information Systems Engineering (CAiSE '03), Klagenfurt/Velden, Austria, 16-20 June, 2003, workshops proceedings}, booktitle = {The 15th Conference on Advanced Information Systems Engineering (CAiSE '03), Klagenfurt/Velden, Austria, 16-20 June, 2003, workshops proceedings}, editor = {Eder, Johann}, publisher = {Techn. Univ.}, address = {Aachen}, isbn = {86-435-0552-8}, pages = {317 -- 328}, language = {en} } @misc{KuehhornBeirowSchrapeetal., author = {K{\"u}hhorn, Arnold and Beirow, Bernd and Schrape, Sven and Golze, Mark and Kn{\"o}pke, Martin}, title = {Simulation fluidged{\"a}mpfter Strukturschwingungen mittels partitionierter Fluid-Struktur-Kopplung}, series = {Forum der Forschung}, volume = {9}, journal = {Forum der Forschung}, number = {18}, issn = {0947-6989}, pages = {79 -- 86}, language = {de} } @incollection{MartinHirsch, author = {Martin, Bernd and Hirsch, Tobias}, title = {Modular Strata of Deformation Functors}, series = {Computational commutative and non-commutative algebraic geometry, proceedings of the Nato Advanced Research Workshop on Computational Commutative and Non-Commutative Algebraic Geometry, Chisinau, Moldova, 6 - 11 June 2004}, booktitle = {Computational commutative and non-commutative algebraic geometry, proceedings of the Nato Advanced Research Workshop on Computational Commutative and Non-Commutative Algebraic Geometry, Chisinau, Moldova, 6 - 11 June 2004}, publisher = {IOS Press}, address = {Amsterdam [u.a.]}, isbn = {1-586-03505-3}, pages = {156 -- 166}, language = {en} } @misc{MartinPochekutov, author = {Martin, Bernd and Pochekutov, Dimitry}, title = {Discriminant and Singularities of Logarithmic Gauss Map, Examples and Application}, series = {Journal of Siberian Federal University, Mathematik \& Physics}, volume = {6}, journal = {Journal of Siberian Federal University, Mathematik \& Physics}, number = {1}, issn = {1997-1397}, pages = {74 -- 85}, abstract = {The study of hypersurfaces in a torus leads to the beautiful zoo of amoebas and their contours, whose possible configurations are seen from combinatorial data. There is a deep connection to the logarithmic Gauss map and its critical points. The theory has a lot of applications in many directions. In this report we recall basic notions and results from the theory of amoebas, show some connection to algebraic singularity theory and discuss some consequences from the well known classification of singularities to this subject. Moreover, we have tried to compute some examples using the computer algebra system SINGULAR and discuss different possibilities and their effectivity to compute the critical points. Here we meet an essential obstacle: Relevant examples need real or even rational solutions, which are found only by chance. We have tried to unify different views to that subject.}, language = {en} } @misc{ViehwegerSchoelzkeSchierz, author = {Viehweger, Bernd and Sch{\"o}lzke, Thomas and Schierz, Martin}, title = {Dr{\"u}cken strukturierter Feinbleche}, series = {B{\"a}nder, Bleche, Rohre : bbr}, volume = {54}, journal = {B{\"a}nder, Bleche, Rohre : bbr}, number = {6}, pages = {122 -- 123}, language = {de} } @misc{SteffensBeckerAmkreutzetal., author = {Steffens, S. and Becker, C. and Amkreutz, Daniel and Klossek, Andr{\´e} and Kittler, Martin and Chen, Y.-Y. and Schnegg, Alexander and Klingsporn, Max and Abou-Ras, Daniel and Lips, Klaus and Rech, Bernd}, title = {Impact of Dislocations and Dangling Bond Defects on The Electrical Performance of Crystalline Silicon Thin Films}, series = {Applied Physics Letters}, volume = {105}, journal = {Applied Physics Letters}, number = {2}, issn = {1077-3118}, doi = {10.1063/1.4890625}, pages = {022108}, language = {en} } @misc{KlossekMankovicsArguirovetal., author = {Klossek, Andre and Mankovics, Daniel and Arguirov, Tzanimir V. and Ratzke, Markus and Kirner, Simon and Friedrich, Felice and Gabriel, Onno and Stannowski, Bernd and Schlatmann, Rutger and Kittler, Martin}, title = {Growth process of microcrystalline silicon studied by combined photoluminsescence and Raman investigations}, series = {Journal of applied physics}, volume = {114}, journal = {Journal of applied physics}, issn = {1520-8850}, doi = {10.1063/1.4838058}, pages = {223511}, language = {en} } @inproceedings{LipsSchulzeStarretal., author = {Lips, Klaus and Schulze, Tim F. and Starr, David E. and B{\"a}r, Marcus and Wilks, Regan G. and Fenske, F. and Ruske, Florian and Reiche, Martin and Krol, Roel van de and Reichardt, Gerd and Sch{\"a}fers, Franz and Hendel, Stefan and Follath, Rolf and Bahrdt, Johannes and Peredkov, Sergey and DeBeer, Serena and H{\"a}vecker, Michael and Knop-Gericke, Axel and Rau, Bj{\"o}rn and Kaufmann, Christian and Schlatmann, Rutger and Schl{\"o}gl, Robert and Rech, Bernd and Raoux, Simone}, title = {EMIL: The Energy Materials In-situ Laboratory Berlin - A novel characterization facility for photovoltaic and energy materials}, series = {31st European Photovoltaic Solar Energy Conference and Exhibition, proceedings of the international conference held in Hamburg, Germany, 14 -18 September 2015}, booktitle = {31st European Photovoltaic Solar Energy Conference and Exhibition, proceedings of the international conference held in Hamburg, Germany, 14 -18 September 2015}, publisher = {WIP}, address = {M{\"u}nchen}, isbn = {3-936338-39-6}, doi = {10.4229/EUPVSEC20152015-1AO.2.1}, pages = {25 -- 28}, language = {en} } @techreport{BoettgerFelgentreffHesseetal., author = {B{\"o}ttger, Stefan and Felgentreff, Bernd and Hesse, Gerold and Hloucal, Martin-Joseph and Leßmann, Dieter and Mix, Sebastian and Roselt, Kersten and Safarik, Mathias and Schmidt, J{\"o}rg and Steffan, Christoph and Uhlmann, Wilfried}, title = {Seethermie - Innovative W{\"a}rmeversorgung aus Tagebaurestseen - Schlussbericht}, address = {Leipzig}, pages = {146}, language = {de} } @techreport{SaleckiHeinbachHirschletal., author = {Salecki, Steven and Heinbach, Katharina and Hirschl, Bernd and Weidinger, Roman and Sch{\"a}fer-Stradowsky, Simon and Ott, Ralf and Lehnert, Wieland and Kliem, Christine and Altrock, Martin and Umlauf, Florian and Puffe, Matthias}, title = {Finanzielle Beteiligung von betroffenen Kommunen bei Planung, Bau und Betrieb von erneuerbaren Energieanlagen (FinBEE) Ergebnisse f{\"u}r die Windenergie}, publisher = {Studie im Auftrag des Bundesministeriums f{\"u}r Wirtschaft und Energie (BMWi)}, address = {Berlin}, pages = {182}, abstract = {Im vorliegenden Bericht wurden die in Wissenschaft und Praxis diskutierten Instrumente zur finanziellen Beteiligung von Kommunen an EE-Anlagen vertieft analysiert und insbesondere rechtlich gepr{\"u}ft. Dabei kann unterschieden werden zwischen Instrumenten, die an bestehende Abgabenzahlungen an Kommunen ankn{\"u}pfen (Grundsteuer, Gewerbesteuer, Konzessionsabgabe), und Instrumenten, mit denen eine neue Abgabe zugunsten der Kommune geschaffen wird (Sonderabgabe, Außenbereichsabgabe). Auf der Basis dieser Analyse wurde dann ein eigenes Instrument entwickelt (EEG-integrierter Mechanismus) sowie Ausgestaltungsempfehlungen zur Umsetzung. Neben den Instrumenten zur finanziellen Beteiligung von Kommunen wurde aufgrund der politischen Entwicklungen im Laufe des Forschungsvorhabens zus{\"a}tzlich das Angebot verg{\"u}nstigter (B{\"u}rger-)Stromtarife als ein Instrument zur B{\"u}rgerbeteiligung untersucht und ebenfalls mit Ausgestaltungsvorschl{\"a}gen empfohlen.}, language = {de} } @techreport{SaleckiHirschlLehnertetal., author = {Salecki, Steven and Hirschl, Bernd and Lehnert, Wieland and Altrock, Martin and Kliem, Christine and Weidinger, Roman and Sch{\"a}fer-Stradowsky, Simon and Ott, Ralf}, title = {Finanzielle Beteiligung von betroffenen Kommunen bei Planung, Bau und Betrieb von erneuerbaren Energieanlagen. Kurzpapier mit Empfehlungen zur kommunalen und B{\"u}rgerbeteiligung an Windenergieanlagen.}, address = {Berlin}, pages = {28}, abstract = {Das vorliegende Papier pr{\"a}sentiert die von den Gutachter/innen erarbeiteten Vorschl{\"a}ge zur finanziellen Beteiligung von Kommunen und B{\"u}rgerInnen an lokalen Onshore-Windenergieanlagen (WEA). Die beiden empfohlenen kommunalen und B{\"u}rgerbeteiligungsinstrumente wurden im Projektverlauf nach mehreren Kriterien ausgew{\"a}hlt. Ein kommunales Beteiligungsinstrument, das {\"u}ber das EEG finanziert wird, behebt die verfassungs- und finanzverfassungsrechtlichen Probleme, die andere vorgeschlagene Steuer- und Abgabeninstrumente mit sich bringen. Eine privatrechtliche Zahlungsvereinbarung wurde daher im Rahmen unserer umfangreichen Bewertung als vorzugsw{\"u}rdig erachtet und wird hier weiter hinsichtlich eines konkreten Umsetzungsvorschlags ausgearbeitet. Als direktes B{\"u}rgerbeteiligungsinstrument werden verg{\"u}nstigte B{\"u}rgerstromtarife vorgestellt. Auf Empfehlung des Vermittlungsausschusses des Bundestags und Bundesrats und vor dem Hintergrund der hohen Zustimmungswerte der Bev{\"o}lkerung zu diesem Instrument, werden verg{\"u}nstigte B{\"u}rgerstromtarife als B{\"u}rgerbeteiligungsinstrument zur Implementierung neben einem kommunalen Beteiligungsinstrument empfohlen - direkt verkn{\"u}pft mit der kommunalen Beteiligung. Beide Vorschl{\"a}ge f{\"u}hren insgesamt zu j{\"a}hrlichen Zahlungen an die betroffenen Kommunen und B{\"u}rger/innen im Bereich von 20.000 bis 30.000 Euro pro WEA. Dabei wird dem WEA-Betreiber erm{\"o}glicht, alternativ die Zahlungen ausschließlich an die Kommune zu entrichten.}, language = {de} } @misc{FroeschkeYasmenPopovetal., author = {Froeschke, Samuel and Yasmen, Nadia and Popov, Alexey and Schiemenz, Sandra and Wolf, Daniel and Giebeler, Lars and Hantusch, Martin and Gr{\"a}ßler, Nico and B{\"u}chner, Bernd and Schmidt, Peer and Hampel, Silke}, title = {Controlled Nanoplatelet Deposition of 2D Chromium Trihalide Solid Solutions}, series = {Chemistry of Materials}, volume = {35}, journal = {Chemistry of Materials}, number = {11}, issn = {1520-5002}, doi = {10.1021/acs.chemmater.2c03785}, pages = {4136 -- 4148}, abstract = {The two-dimensional (2D) chromium trihalides CrCl3, CrBr3, and CrI3 are most famous for their exotic magnetic properties when their crystals get downscaled to nanometer dimensions. One way to tune the properties of such materials and to further increase their potential utility, e.g., in spintronics, is the formation of solid solutions. Here, we present a detailed theoretical and experimental study on the synthesis and nanoplatelet growth of CrBrxCl3-x and CrBrxI3-x solid solutions. Phase pure powder was obtained by tempering the respective parent compounds at 600 and 550 °C, using additional iodine in the case of CrBrxI3-x. The dominant stacking order changes at x = 1.8 for CrBrxCl3-x while remaining similar to CrI3 for the whole CrBrxI3-x series. A consecutive chemical vapor transport from 575 → 525 °C for 2 h (CrBrxCl3-x) or 600 → 550 °C for 3 h with 0.1 mmol additional iodine (CrBrxI3-x) resulted in the deposition of high-quality nanoplatelets on a substrate with only several nanometers in height. The composition can be controlled by the choice of the starting material, since only small shifts in the anion ratio occur during the transport. The deposited CrBrxCl3-x nanoplatelets can then be easily delaminated by ultrasonication in ethanol to reduce the height even further to few-layer dimensions. These nanoplatelets could potentially be used to investigate the property changes (e.g., in terms of magnetic response) for the downscaling of these solid solutions. We further demonstrate the quality of the deposited material by transmission electron microscopy, selected area electron diffraction, and X-ray photoelectron spectroscopy. Raman spectroscopy of the solid solution series reveals a complex evolution of vibrational modes. Photoluminescence measurements on solid solution samples show emission peaks in the near-infrared energy range with the specific energy and intensity being composition and temperature dependent.}, language = {en} }