title: Atomic Scale Imaging of Nucleation and Growth Trajectories of an Interfacial Bismuth Nanodroplet.
abstract: Because of the lack of experimental evidence, much confusion still exists on the nucleation and growth dynamics of a nanostructure, particularly of metal. The situation is even worse for nanodroplets because it is more difficult to induce the formation of a nanodroplet while imaging the dynamic process with atomic resolution. Here, taking advantage of an electron beam to induce the growth of Bi nanodroplets on a SrBi2Ta2O9 platelet under a high resolution transmission electron microscope (HRTEM), we directly observed the detailed growth pathways of Bi nanodroplets from the earliest stage of nucleation that were previously inaccessible. Atomic scale imaging reveals that the dynamics of nucleation involves a much more complex trajectory than previously predicted based on classical nucleation theory (CNT). The monatomic Bi layer was first formed in the nucleation process, which induced the formation of the prenucleated clusters. Following that, critical nuclei for the nanodroplets formed both directly from the addition of atoms to the prenucleated clusters by the classical growth process and indirectly through transformation of an intermediate liquid film based on the Stranski-Krastanov growth mode, in which the liquid film was induced by the self-assembly of the prenucleated clusters. Finally, the growth of the Bi nanodroplets advanced through the classical pathway and sudden droplet coalescence. This study allows us to visualize the critical steps in the nucleation process of an interfacial nanodroplet, which suggests a revision of the perspective of CNT.
authors.affiliation: Laboratory of Environmental Sciences and Technology, Xinjiang Technical Institute of Physics & Chemistry, Key Laboratory of Functional Materials and Devices for Special Environments, Chinese Academy of Sciences , Urumqi, 830011, China.
authors.forename: Yingxuan
authors.initials: Y
authors.lastname: Li
authors.affiliation: Nano Institute of Utah and Department of Materials Science and Engineering, University of Utah , Salt Lake City, Utah 84112, United States.
authors.forename: Benjamin R
authors.initials: BR
authors.lastname: Bunes
authors.affiliation: Nano Institute of Utah and Department of Materials Science and Engineering, University of Utah , Salt Lake City, Utah 84112, United States.
authors.forename: Ling
authors.initials: L
authors.lastname: Zang
authors.affiliation: Laboratory of Environmental Sciences and Technology, Xinjiang Technical Institute of Physics & Chemistry, Key Laboratory of Functional Materials and Devices for Special Environments, Chinese Academy of Sciences , Urumqi, 830011, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Zhao
authors.affiliation: Laboratory of Environmental Sciences and Technology, Xinjiang Technical Institute of Physics & Chemistry, Key Laboratory of Functional Materials and Devices for Special Environments, Chinese Academy of Sciences , Urumqi, 830011, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Li
authors.affiliation: Laboratory of Environmental Sciences and Technology, Xinjiang Technical Institute of Physics & Chemistry, Key Laboratory of Functional Materials and Devices for Special Environments, Chinese Academy of Sciences , Urumqi, 830011, China.
authors.forename: Yunqing
authors.initials: Y
authors.lastname: Zhu
authors.affiliation: Laboratory of Environmental Sciences and Technology, Xinjiang Technical Institute of Physics & Chemistry, Key Laboratory of Functional Materials and Devices for Special Environments, Chinese Academy of Sciences , Urumqi, 830011, China.
authors.forename: Chuanyi
authors.initials: C
authors.lastname: Wang
keywords: Bi nanodroplet; atomic resolution; growth; in situ imaging; nucleation