How Sensitive is Epitaxial Growth to Adsorbates?

CO coverages as low as ${10}^{-3\mathrm{}}$ monolayers—which may result from background partial pressures in the low ${10}^{-11\mathrm{}}$ mbar range—are found to affect island shapes, island densities, step-edge barriers for adatoms and film roughness during homoepitaxial growth on Pt(111). The effects are traced to preferential adsorption of CO molecules on low coordinated Pt atoms.