Thermal evolution of Co islands on Ag/Si(111)- √3 × √3 and Ag/Ge(111)- √3 × √3 surfaces

Thermal evolution of Co islands on Ag/Ge(1111) √3 × 3 and Ag/Si(111)- √ 3 × √3 surfaces was studied by scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED). Ag-√3 × √3 buffer layer can avoid alloy formation of Co and Si or Ge below the annealing temperature 500 °C. The growth behavior of Co on Ag/Si(111)√3 × √3 surfaces is very different from that on Ag/Ge(111)-√3 × √3 surfaces, although both the √3 structures can be classified as honeycomb chain trimer (HCT) model. Submonolayer Co on Ag/Si(111)-√3 × √3 surfaces prefer to form clusters below 500 °C. However, Co clusters nucleate and construct two-dimensional islands (2D islands) on Ag/Ge(111)-√3 × √3 surfaces after annealing to 300 °C. The result of different growth behavior comes from two major factors. One is antiphase boundaries (APBs) with extra electron states, which trap Co clusters on Ag/Si(111)-√3 × √3 surfaces. The other is the strong binding force that exists between Ge and Co atoms to cause the formation of Co period islands on Ag/Ge(111)-√3 × √3 surfaces.