Heterointerface Effect on Two-Step Nucleation Mechanism of Bi Particles.

The nucleation and crystallization of Bi particles on two matrices, crystalline bismuth sulfide ( c -Bi 2 S 3 ) and amorphized bismuth titanium oxide ( a -Bi 12 TiO 20 ), 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 -Bi 2 S 3 and a -Bi 12 TiO 20 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 -Bi 2 S 3 but free from matrix effects on a -Bi 12 TiO 20 . The matrix effect on the two-step nucleation mechanism was demonstrated from a thermodynamic point of view.