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

Abstract

Single crystals of rhombohedral KBiS 2 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 K 2 S 5 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 rhombohedral KBiS 2 to be a semiconductor with an indirect band gap, which was confirmed by experiment. This study demonstrates how nondestructive tomographic imaging and 3D crystallography methods can lead to advances in discovering new materials and studying crystal growth mechanisms.

Informing quantum materials discovery and synthesis using X-ray micro-computed tomography

“…Where the hyperspectral detector allows for elemental analysis, Diffraction µ-Computed Tomography (DCT) allows for orientation analysis of 3D volumes of both polycrystalline and single crystalline samples 57 . This has already had some use in ceramics to track grain growth while sintering and has been shown to inform crystal morphology in materials discovery 58,59 . Being able to follow grain selection in floating zone growths using DCT could be used alongside current methods to allow for a better optimization of growth conditions 60 .…”