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-depended 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 bulk-WSe2 from 900 °C to 820 °C with a dwell time of 72 h, while right-handed spiral nanocrystals are obtained from 850 °C to 800 °C with a dwell time of 60 min. Left-handed spirals occur 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 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 exhibit step heights of around 10 nm. Electron backscatter diffraction pattern reveal a convex curvature for WSe2 with the curvature radii determined as Rx = (270 ± 32) µm and Ry = (141 ± 9) µm, respectively.
