Growth of Pb islands on Ge(111) - evaluating temperature dependence from experiments and data analytics*

The growth of single crystal metal islands on semiconductor surfaces is an important technological process that also raises fundamental questions about interactions at the metal-semiconductor interface. In our joint experimental and theoretical examination of the growth of Pb on Ge(111), Low Energy Electron Microscopy (LEEM) measurements at -20^oC, -30^oC, -40^oC, and -50^oC in real time reveal initially the formation of a Pb wetting layer until a critical coverage q_c when nanocrystalline Pb islands abruptly formed. Using data analytic techniques, we analyzed the LEEM images to determine the island area and density as a function of deposited amount. The growth rates are high indicating that the collection area is beyond from what expected by random walk diffusion. We found that the growth rates of island area increase by a factor of 4 within the range  -20^oC to -50^oC. We also found that the average size of each island strongly depends on the depositing temperature, i.e., the lower the temperature the smaller is the island size. Our results suggest that by controlling the deposition temperature the size of the grown Pb island can be selectively controlled.