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 -