Heterointerface Effect on Two-Step Nucleation Mechanism of Bi Particles

The nucleation and crystallization of Bi particles on two matrices, crystalline bismuth sulfide (c-Bi2S3) and amorphized bismuth titanium oxide (a-Bi12TiO20), were studied by using in situ transmission electron microscopy (TEM) analysis. The atomic structures of the Bi particles were monitored by acquiring high-resolution TEM images in real time. The Bi particles were grown on c-Bi2S3 and a-Bi12TiO20 via a two-step nucleation mechanism; dense liquid clusters were clearly observed at the initial stage of nucleation, and the coalescence of clusters was frequently observed during the growth. However, the nucleation and crystallization behaviors of Bi particles were governed by the matrix; in particular, the evolution of their morphology and atomic structure was confined on c-Bi2S3 but free from matrix effects on a-Bi12TiO20. The matrix effect on the two-step nucleation mechanism was demonstrated from a thermodynamic point of view.