In Situ Atomic‐Scale Study of Particle‐Mediated Nucleation and Growth in Amorphous Bismuth to Nanocrystal Phase Transformation

Abstract

Understanding classical and nonclassical mechanisms of crystal nucleation and growth at the atomic scale is of great interest to scientists in many disciplines. However, fulfilling direct atomic‐scale observation still poses a significant challenge. Here, by taking a thin amorphous bismuth (Bi) metal nanosheet as a model system, direct atomic resolution of the crystal nucleation and growth initiated from an amorphous state of Bi metal under electron beam inside an aberration‐corrected transmission electron microscope is provided. It is shown that the crystal nucleation and growth in the phase transformation of Bi metal from amorphous to crystalline structure takes place via the particle‐mediated nonclassical mechanism instead of the classical atom‐mediated mechanism. The dimension of the smaller particles in two contacted nanoparticles and their mutual orientation relationship are critical to governing several coalescence pathways: total rearrangement pathway, grain boundary migration‐dominated pathway, and surface migration‐dominated pathway. Sequential strain analyses imply that migration of the grain boundary is driven by the strain difference in two Bi nanocrystals and the coalescence of nanocrystals is a defect reduction process. The findings may provide useful information to clarify the nanocrystal growth mechanisms of other materials on the atomic scale.

Hybrid Growth Modes of PbSe Nanocrystals with Oriented Attachment and Grain Boundary Migration

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Nanoscale Imaging and Stabilization of Silica Nanospheres in Liquid Phase Transmission Electron Microscopy

“…However, one of the main limitations of conventional TEM is that the sample can only be imaged in a vacuum. Although the electron beam can be utilized to drive nanoscale dynamic processes in this environment, the possibilities to study such processes taking place in gaseous or liquid environment, such as fabrication of microelectromechanical systems (MEMS) and microsupercapacitors (MSC), nanoparticle formation, and catalyst synthesis, are severely limited. Recently developed liquid phase TEM (LP‐TEM) offers a means to overcome this challenge, allowing samples to be imaged in a liquid with nanoscale spatial resolution and high temporal resolution .…”

Size‐Dependent Phase Transformation of Noble Metal Nanomaterials

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