Unveiling the Nucleation Dynamics and Growth Mechanism of Layered MoS2 from Crystalline K2MoS4 by in Situ Transmission Electron Microscopy

Understanding the chemical reaction kinetics and nucleation process in materials synthesis is significant for accurately regulating the size, morphology, and crystal structure of materials. In this article, we studied the chemical reaction and materials transformation from solid crystalline precursor K2MoS4 to polycrystalline MoS2 in a high-resolution transmission electron microscope at the atomic level. Through real time investigations, the nucleation dynamics and growth mechanism of layered MoS2 from precursor K2MoS4 were captured, identified, and revealed. It was found that MoS2 nanocrystals can nucleate and grow not only along the well-expected low-index planes, but also along the high-index planes of the original precursor K2MoS4. These MoS2 nanocrystals with different crystal orientations contact and coalesce to form a larger nanocrystal through the oriented attachment mode. Afterward, the growth and coalescence of these nanocrystals lead to the formation of a densely packed layered MoS2 polycrystalline film. This study provides new insights into the nucleation and growth dynamics of materials and provides a promising way to investigate reaction dynamics on an atomic scale.