| Nucleation and growth mechanisms of ion etching of Cu(100) and surfactant (Sb) mediated Ag growth on Ge(100) were studied in ultra-high vacuum (UHV) using scanning tunneling microscopy (STM), low energy electron diffraction (LEED), temperature programmed desorption (TPD), and low energy ion scattering spectroscopy (LEISS). The formation of vacancy clusters from ion etching was characterized and could be modeled and understood as the reverse of film growth. The results suggest that a barrier exists for vacancies to ascend steps. This additional barrier also contributes to pit ordering. The interaction of the Sb with Ge was investigated. Antimony was found to form intermixed surface with Ge. The intermixing, however, could be controlled by deposition and annealing temperatures and Sb coverage. The growth of Ag with and without Sb on Ge(100) was studied and compared. Without Sb, Ag formed elongated 2D islands and 3D clusters. A new metastable Ag-Ge surface alloy phase was found when Ag was deposited at 470 K. This alloy phase can only be obtained by deposition at 470 K. Annealing to 470 K gave a surface with 3D clusters only. When Sb was used as a surfactant for Ag growth, no surface alloy was observed and the cluster shape was isotropic instead of rectangular. On the Sb covered surface, nucleation appeared to be dominated by defects at low temperatures. At higher temperatures, Sb increased the diffusion barrier for Ag. Other effects of using Sb on Ag growth included increase in cluster density and decrease in cluster size. Antimony did not work as a conventional surfactant since it did not segregate to the top of the film at elevated temperatures. |
