Growth Dynamics of Gallium Nanodroplets Driven by Thermally Activated Surface Diffusion

The growth of catalytic liquid-metal nanodroplets on flat substrates is essential for many technological applications. However, the detailed nucleation and growth dynamics of these nanodroplets remain unclear. Here, using in situ transmission electron microscopy (TEM) imaging, we track in real time the growth of individual Ga nanodroplets from a beam of Ga vapor. We show that the nucleation and growth are driven by thermally activated surface diffusion of Ga adatoms, with the diffusion activation energy of E_D = 95 ± 10 meV on a SiN surface. More importantly, our analysis shows that Ga dimers serve as the critical nucleation clusters and that the nanodroplet growth follows a power-law of the form R(t) ∝ e^-(t - t₀)^1/2. These insights into the growth dynamics of metallic nanodroplets are essential for tailoring their size and density for their application in self-catalyzed growth of nanomaterials.