Pinning disfavors nucleation in colloidal vapor deposition

Vapor deposition, known for precise structural control, is inevitably influenced by impurities. These impurities, often distinct from the depositing material, can significantly impact material properties, including local structure. Interestingly, the effect of immobilizing some of the depositing particles themselves, which would still preserve local structural symmetry, remains largely unexplored. By introducing a small fraction of pinned sites during colloidal vapor deposition and employing a combination of thermodynamic and kinematic measurements, we demonstrate that pinned sites, termed as "mobility impurities," are disfavored as nucleation centers. Moreover, tuning the mobility of mobile colloids can adjust nucleation likelihood. In later stages of growth, pinning induces mode localization, altering the thin film's vibrational spectrum. Our research thus underscores the potential of strategically incorporating mobility impurities to engineer material properties.