Ultrathin BiOCl crystals grown in highly disordered vapor micro-turbulence for deep ultraviolet photodetectors

Crystallization, while a common process in nature, remains one of the most mysterious phenomena. Understanding its physical mechanisms is essential for obtaining high-quality crystals. Typically, crystals grown by thermal evaporation or sublimation nucleate the substrate facing the evaporation source. Here, a novel vapor micro-turbulence mass transport mechanism in the growth process of ultrathin BiOCl single crystals has been revealed. In this mechanism, the precursor vapor bypasses the solid substrate, forming micro-turbulent vaporizing flows to nucleate on the surface of the substrate facing away from the evaporation source. Considering nucleation kinetics, fast shear flows are known to cause secondary nucleation, increasing nucleation quantity while decreasing the final size of the crystals. Thus, the nucleation and growth process of BiOCl crystals are controlled by adjusting the micro-turbulence intensity to reduce shear flow energy and dilate phase distribution, resulting in BiOCl crystals with uniform distribution and regular shape. Subsequent structural and morphological characterization confirms the high crystallization quality of the obtained crystals, and the performance of the constructed solar-blind photodetectors is comparable to that of similar devices. These findings contribute to a deeper understanding of vapor mass transport and crystal growth techniques and may be useful for applications related to metal oxide crystals.

Graphical abstract