We have performed a systematic study on the influence of deposition energy on the morphology of submonolayer Co films grown on Ag(001) at ambient temperature. Co was deposited by low-energy ion deposition with a deposition energy between 5 and 30 eV. The island density, height, size distribution, and composition were studied using scanning tunneling microscopy. For increasing deposition energy, there is an increasing fraction of Co incorporated in the first monolayer of the surface. These Co atoms form surface-confined clusters, which can act as pinning centers for Co adatoms on top of the surface. These pinning centers promote an increase in island density compared to deposition with thermal particles (similar to0.1 eV). In addition, our experimental results indicate that both ion impact induced island fragmentation and dissociation play an important role during nucleation and growth. Island fragmentation is a mechanism that promotes an increase in island density compared to thermal deposition, whereas island dissociation promotes a decrease in island density.