First-principles Study of Ag Stripe Formation on the Ni(110) Surface

The stability of monolayer-thick Ag stripes formed on the Ni(110) surface was studied using first-principles calculations.The Ag stripes were found to be the aggregation of one-dimensional (1-D) silver (Ag) clusters along the ½1 " 10 direction between the Ni(110) rows, and the clusters extended in the [001] direction to form stripes. Due to the large lattice mismatch between the adsorbed Ag and the Ni substrate, 1-D Ag clusters were not stable with more than seven atoms, and the edge atoms at the 1-D clusters tended to dissociate.The diffusion barriers for the dissociation of the 1-D Ag cluster edges were evaluated using the nudged elastic band method and found to be 0.41 eV for a two-Ag atom cluster (n = 2) and 0.14 eV for a ten-Ag atom cluster (n = 10).Considering surface relaxation of the substrate Ni atoms in the 〈001〉 directions, the diffusion barrier further decreased by ~0.06 eV, which explains the experimental scanning tunneling microscopy images.It was also found that 1-D Ag clusters aggregated to form stripes extending in the [001] direction due to the effect of substrate strain and the one dimensional band formation of Ag 5s-derived states in the stripe direction.[001][110] 8 nm×8 nm Ag/Ni(110) 0.74 ML Ag/Ni(110) 0.74 ML -0.10 -0.05 0.00 0.05 0.10 0.15 0.20 0 1 2 3 4 5 6 7 8 9 10 11 12 n δE (eV) Ag Ni Dissociation