Mechanism of non-catalytic chemical vapor deposition growth of all-inorganic CsPbX₃(X = Br, Cl) nanowires

The growth of high-quality nanostructures using chemical vapor deposition (CVD) normally requires metal catalysts, which when incorporated in the nanostructures may severely affect their properties. Here, we report on the non-catalytic CVD growth of all-inorganic CsPbX₃(X = Br, Cl) perovskite nanowires (NWs) with an emphasis on understanding the growth mechanismviadetailed electron microscopy and spectroscopic studies at different stages of the growth. We show that the chemical vapors initiate the nucleation and growth of halide nanoparticles, followed by structural transformations through axial elongation into nano-capsules and dumbbells, and eventually these dumbbells meet and form complete NWs. This growth mechanism is independent of the substrate crystallinity and detailed spectroscopic measurements demonstrate that nanoscale features at different growth stages have similar material properties as the final NWs. We believe that this self-assembly mechanism can be extended to understand the evolution of nanostructures in other semiconductor materials and to tune their characteristics to enhance their functionalities for novel optoelectronic devices.