Effect of a surfactant in homoepitaxial growth of Ag (001): dendritic versus faceted island morphologies

The homoepitaxial growth of Ag(001) has been investigated in real time with X-ray diffraction by recording two-dimensional intensity distributions of the scattered intensity while the film was growing. a narrow range of growth parameters around T=320 K and rate=0.02 layers/s, the surface diffuse scattering, which provides information on the morphology of the surface islands, exhibits a peculiar cross-shaped pattern, which has been interpreted as being due to dendritic island morphology. The dendritic islands evolve to the faceted morphology characteristic of the equilibrium shape when the surface temperature is increased. If, prior to the growth, a small coverage of surfactant atoms is deposited on the surface, then the morphology of the growing islands at 320 K is not dendritic, as for the clean surface, but faceted. These findings provide new insights on the mechanisms underlying the effect of the surfactant.