Morphology and Growth Habit of the New Flux-Grown Layered Semiconductor KBiS2 Revealed by Diffraction Contrast Tomography

Single crystals of rhombohedral KBiS2 were synthesized for the first time, and the structure, growth habit, and properties of this layered semiconductor are presented. The single crystals form from a reactive K2S5 salt flux and are still embedded in the residual flux, without removal from the reaction vessel throughout the whole study. Laboratory diffraction contrast tomography (LabDCT) was used to identify the crystalline phase, orientation, and microstructure of the crystals. Meanwhile, powder and single-crystal X-ray diffraction were used to determine detailed crystallographic information. The morphology of the crystalline assemblies observed by absorption contrast tomography reveals screw-dislocation-driven growth to be the dominant mechanism. First-principles electronic structure simulations predict rhombohe-dral KBiS2 to be a semiconductor with an indirect band gap, which was confirmed by experiment. This study demonstrates how non-destructive tomographic imaging and 3D crystallography methods can lead to advances in discovering new materials and studying crystal growth mechanisms.