We examined the adsorption and subsequent migration of a silver monomer (Ag1), a dimer (Ag2), and a tetramer (Ag4) on the group IV(001) (IV = C, Si, and Ge) semiconductor surfaces, using density functional theory. For Ag1 on IV(001), the adsorption is favored to be covalently attached at the trench between the substrate rows, yielding the heats of adsorption of 1.91, 2.53, and 2.07 eV on C(001), Si(001), and Ge(001), respectively. The migration of Ag1 is, however, by way of the substrate rows regardless of the migration direction, giving isotropic barriers of 0.08, 0.51, and 0.38 eV on C(001), Si(001), and Ge(001), respectively. As the size of silver species increases, there emerge quasi-covalent adsorbate-adsorbate (Ag-Ag) interactions, in addition to the covalent adsorbate-substrate interactions, as showcased by the adsorption of Ag2 and Ag4 on Si(001). The heats of adsorption are 2.16 eV for Ag2 and 2.53 eV for Ag4. Consequently, the migration of Ag2 and Ag4 is enabled inside the trench between Si rows, leading to anisotropic barriers; that is, Ag2 favors migrating across (0.26 eV in the barrier) over along (0.63 eV in the barrier) Si rows, whereas Ag4 favors migrating along (0.24 eV in the barrier) over across (0.68 eV in the barrier) Si rows.
|Journal||Journal of Physical Chemistry C|
|State||Published - 28 Apr 2022|