TY - GEN A1 - Putze, Philipp A1 - Ritschel, Tobias A1 - Chekhonin, Paul A1 - Geck, Jochen A1 - Wolf, Daniel A1 - Popov, Alexey A1 - Büchner, Bernd A1 - Schmidt, Peer A1 - Hampel, Silke T1 - Creating chirality in WSe₂ through screw dislocations by chemical vapor transport T2 - Nanoscale horizons N2 - Screw dislocation-driven nanostructures of two-dimensional transition metal dichalcogenides (2D TMDs) can feature chirality that enables prominent asymmetric optical properties. One of the outstanding representatives is WSe₂ as it can exhibit intriguing new size and shape-dependent chemical and physical properties compared to its bulk counterpart. Crystal growth control in nanostructures with screw dislocation-driven growth is central for exploiting their structure-related properties. However, bottom-up syntheses of 2D TMDs usually contain ‘trial and error’ approaches. Here we report on the rational synthesis planning and realizing for the binary system W:Se to achieve chirality in nano-scale crystals by chemical vapor transport (CVT). For that purpose, key parameters were modelled based on thermodynamic datasets. Thus, crystal growth by CVT under addition of SeCl4 succeeds for right-handed spiral nanocrystals from 850 °C to 800 °C with a dwell time of 60 min, while left-handed spirals are obtained from 915 °C to 860 °C. Surface-fused SiO₂ nanoparticles on an Si(100) substrate served as potential nucleation points. Chirality of screwed WSe₂ was unprecedentedly investigated by circular-polarized Raman Spectroscopy and showed an intensity increase of the E¹₂g mode of 29% and 15% for right and left-handed spirals, respectively. Pyramid-like WSe2 analyzed by atomic force microscopy exhibits step heights of around 10 nm. Electron backscatter diffraction patterns reveal a convex curvature for WSe₂ with the curvature radii determined as Rx = (270 ± 32) μm and Ry = (141 ± 9) μm, respectively. KW - Chrystal growth KW - Chemical vapor transport KW - Thermodynamic modeling KW - 2D layered compounds KW - Chalcogenides Y1 - 2025 UR - https://pubs.rsc.org/en/content/articlelanding/2025/nh/d4nh00567h U6 - https://doi.org/10.1039/D4NH00567H VL - 10 IS - 5 SP - 944 EP - 956 PB - Royal Society of Chemistry CY - Cambridge ER - TY - GEN A1 - Putze, Philipp A1 - Wolf, Daniel A1 - Chekhonin, Paul A1 - Popov, Alexey A1 - Ritschel, Tobias A1 - Lubk, Axel A1 - Geck, Jochen A1 - Büchner, Bernd A1 - Schmidt, Peer A1 - Hampel, Silke T1 - Twisted and screw dislocation-driven growth of MoSe₂ nanostructures by chemical vapor transport T2 - Nano research N2 - Twisted multilayers of two-dimensional materials attract widespread research interest due to their intriguing electronic and optical properties related to their chiral symmetry breaking and Moiré effects. The two-dimensional transition metal dichalcogenide MoSe₂ is a particular promising material for twisted multilayers, capable of sustaining Moiré excitons. Here, we report on a rational bottom-up synthesis approach for twisted MoSe₂ flakes by chemical vapor transport (CVT). Screw dislocation-driven growth was forced by surface-fused SiO₂ nanoparticles on the substrates that serve as potential nucleation points in low supersaturation condition. Thus, crystal growth by in-situ CVT under addition of MoCl₅ leads to bulk 2H-MoSe₂ in a temperature gradient from 900 °C to 820 °C with a dwell time of 96 h. Hexagonally shaped 2H-MoSe₂ flakes were grown from 710 °C to 685 °C with a dwell time of 30 min on SiO₂@Al₂O₃(0001) substrates. Electron backscatter diffraction as well as electron microscopy reveals the screw dislocation-driven growth of triangular 3R-MoSe₂ with individual step heights between 0.9 nm and 2.9 nm on SiO₂@Si(100) under the same conditions. Finally, twisted MoSe₂ flakes exhibiting a twist angle of 19° with respect to the [010] zone axis could be synthesized. KW - Chrystal growth KW - Chemical vapor transport KW - Thermodynamic modeling KW - 2D layered compounds KW - Chalcogenides Y1 - 2025 UR - https://www.sciopen.com/article/10.26599/NR.2025.94908020 U6 - https://doi.org/10.26599/NR.2025.94908020 SN - 1998-0000 IS - 18 SP - 1 EP - 23 PB - Tsinghua University Press ER - TY - VIDEO A1 - Michalk, Silke A1 - Bartholomäus, Heike A1 - Schmidt, Peer T1 - Von starren Grenzen zu freien Wegen : die Entfaltung von Bildungspotenzialen T2 - University:Future Festival (U:FF), 13. bis 15. Mai 2025 N2 - Wie kann Studium neu gedacht werden? Die BTU Cottbus-Senftenberg diskutiert ein zukunftsfähiges Hochschulmodell, das Profillinien, Microcredentials und Future Skills integriert. Im Rahmen der Neugestaltung der Rahmenstudienordnungen und im Kontext der Empfehlungen des Wissenschaftsrates zur Weiterentwicklung des Hochschulsystems Brandenburg entsteht ein zukunftsfähiges Hochschulmodell, das Durchlässigkeit, Flexibilität und Qualität vereint. Der Transformationsprozess setzt auf die Schaffung individueller Bildungswege entlang des gesamten, weiter gefassten Student Life Cycles, wodurch die Attraktivität des Studiums und der Studienerfolg gesteigert werden. KW - Flexibilisierung KW - Microcredentials KW - Future Skills Y1 - 2025 UR - https://www.youtube.com/watch?v=Vilb_MeAC-0&t=457s ER - TY - RPRT A1 - Schmidt, Peer A1 - Giese, Marie A1 - Heinemann, Robert A1 - Nawdiyal, Amruta A1 - Knorr, Monika A1 - Breitkopf, Cornelia A1 - Schneegans, Marcel Felix A1 - Pinnau, Sebastian A1 - Lorenz, Tommy A1 - Mickoleit, Erik A1 - to Baben, Moritz A1 - Keuter, Philipp A1 - Müller, Michael A1 - Sergeev, Dmitry A1 - Ewaznezhad Fard, Darya A1 - Morsa, Amedeo A1 - Rhys, Dominic Jacob A1 - Yazhenskikh, Elena T1 - PCM-Screening-2 : Evaluierung eutektischer Gemische für den Einsatz als PCM : thermodynamische Modellierung und experimentelle Methoden - 2 T2 - Deutsche Forschungsberichte N2 - Durch den Einsatz von Wärme- und Kältespeichern in Gebäuden, Industrieanlagen und Kraftwerken können Lastschwankungen reduziert und die Anlageneffizienz verbessert werden. Latentwärmespeicher (PCM) ermöglichen durch Ausnutzung einer fest-flüssig Phasenumwandlung hohe Speicherdichten bei geringen Temperaturdifferenzen. Die Verfügbarkeit geeigneter und kostengünstiger PCM’s ist derzeit noch eingeschränkt. Ein Screening geeigneter Stoffsysteme zur Bildung multinärer Eutektika durch thermodynamische Modellierung der Phasengleichgewichte erlaubt fundierte Vorhersagen zur Zusammensetzung eutektischer Gemische, ihren Schmelztemperaturen und -enthalpien. Auf Basis der Literatur, umfangreicher experimenteller Untersuchungen und Simulationen wurde im Projekt eine im Temperaturbereich nicht eingeschränkte thermochemische Datenbank für das komplexe Stoffsystem Na+, K+, Ca2+, Mg2+ // Cl−, NO3−, SO4_2−, CO3_2− // H2O geschaffen, die eine Auswahl neuer PCM mit optimalen thermodynamischen Eigenschaften für spezifische Prozessanforderungen auf Basis von in Deutschland in großen Mengen verfügbaren, preiswerten Rohstoffen ermöglicht. Weiterhin wurde ein CalPhaD-basiertes Viskositätsmodell, ein Screening-Verfahren inkl. Webserver und intuitive Visualisierungsmöglichkeiten hochkomponentiger Systeme entwickelt. Mittels eines Screenings erfolgte eine Vorauswahl von potentiell als PCM geeigneten Gemischen, die umfangreich charakterisiert wurden. Auf Basis der vielversprechenden Speicherdichten und der niedrigen Materialkosten wird erwartet, dass ein oder mehrere dieser identifizierten PCMs in die Anwendung als thermische Speicher gebracht werden können. N2 - The use of heat and cold storage systems in buildings, industrial plants, and power stations can reduce load fluctuations and improve plant efficiency. Latent heat storage systems (phase change materials - PCM) enable high storage densities with low temperature differences by exploiting a solid-liquid phase transition. The availability of suitable and cost-effective PCMs is currently still limited. Screening suitable material systems for the formation of multinary eutectics through thermodynamic modeling of phase equilibria allows well-founded predictions to be made about the composition of eutectic mixtures, their melting temperatures, and enthalpies. Based on the literature, extensive experimental investigations, and simulations, the project created a thermochemical database for the complex material system Na+, K+, Ca2+, Mg2+ // Cl−, NO3−, SO4_2−, CO3_2− // H2O was created, which enables the selection of new PCMs with optimal thermodynamic properties for specific process requirements based on inexpensive raw materials available in large quantities in Germany. Furthermore, a CalPhaD-based viscosity model, a screening procedure including a web server, and intuitive visualization options for highly component systems were developed. A screening process was used to preselect mixtures potentially suitable as PCMs, which were then extensively characterized. Based on the promising storage densities and low material costs, it is expected that one or more of these identified PCMs can be put into application as thermal storage. KW - PCM KW - Latenwärmespeicher KW - Eutektische Gemische KW - Thermodynamische Daten KW - Thermodynamische Modellierung KW - Anorganische Salzhydrate KW - Anorganische Salze Y1 - 2026 UR - https://oa.tib.eu/renate/handle/123456789/29435 U6 - https://doi.org/10.34657/28504 ER -