Atomic scale in-situ observation of gas-solid interaction regulating the pre-nucleation process of Pd atomic clusters

Advancements in nanotechnology have propelled the understanding of atomic-scale nucleation processes, essential for the evolution of atomic manufacturing. The process of amorphous precursors nucleation showcases a complex transition influenced by various factors. Utilizing aberration-corrected ETEM and theoretical calculation, we explore the nucleation of amorphous Pd atomic clusters. This study examines the nucleation dynamics and gas-solid interaction regulating of Pd clusters on ultrathin carbon films, prepared via electron beam evaporation. HRTEM observation and FFT analysis reveal that, in the early stage of nucleation, Pd cluster growth predominantly follows an Ostwald ripening-like mechanism. Atoms from smaller clusters migrate and attach to larger ones, facilitating their progression to critical nucleation size. Environmental conditions significantly influence this process; hydrogen atmospheres lower the surface energy of Pd clusters, reducing the critical nucleation size, while argon atmospheres impede growth of Pd clusters by occupying migration sites on the carbon surface. These insights into atomic cluster behavior and environmental interactions are crucial for understanding the early stages of nucleation from amorphous to crystalline and can help opens new avenues for the controlled fabrication of materials with optimized functionalities.