  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.
