First-Principle Studies on Adsorption of Cu+ and Hydrated Cu+ Cations on Clean Si(111) Surface

To study the adsorption behavior of Cu+ in aqueous solution on semiconductor surface, the interactions of Cu+ and hydrated Cu+ cations with the clean Si(111) surface were investigated via hybrid density functional theory(B3LYP) and Moller-Plesset second-order perturbation(MP2) method. The clean Si(111) surface was described with cluster models(Si14H17, Si16H20 and Si22H21) and a four-silicon layer slab under periodic boundary conditions. Calculation results indicate that the bonding nature of adsorption of Cu+ on Si surface can be viewed as partial covalent as well as ionic bonding. The binding energies between hydrated Cu+ cations and Si(111) surface are large, suggesting a strong interaction between them. The coordination number of Cu+(H2O)(n) on Si(111) surface was found to be 4. As the number of water molecules is larger than 5, water molecules form a hydrogen bond network. In aqueous solution, Cu+ cations will safely attach to the clean Si(111) surface.