The latter are also observed to form on the Ni/Ge(111)-c(2 × 8) surface but at a higher temperature. After annealing at 670 K, the hexagonal and the long selleck inhibitor islands form in coexistence with all above-mentioned structures. It is likely that the clusters which were initially trapped in the triple-holes develop into regular islands upon annealing. The islands grow
in size with the increase in temperature at the cost of 7 × 7 islands. Finally, at 770 K, the hexagonal and long islands coexist with the triple-holes. Figure 6 Phase diagram for Ni/Ge(111)-c(2 × 8) and Ni/Ag/Ge(111)-√3 × √3 along with corresponding STM images. The notations for the structural phases are indicated in Figures 3,4,5. The formation of defects, differing in appearance (i.e., the ring-like defects on the Ge(111)-c(2 × 8) surface vs. the triple-hole defects on the Ag/Ge(111)-√3 × √3 surface), indicates that the mixing
between Ni and Ge proceeds on both surfaces through different mechanisms. Generally, however, the presence of 1 ML Ag on the Ge(111) surface retards the inter-3-deazaneplanocin A diffusion between Ni adatoms and Ge substrates, at least at temperatures below 670 K. Bafilomycin A1 molecular weight This is why the formation of the Ni-containing 2√7 × 2√7 and the 3 × 3 islands is prevented on the Ag/Ge(111)-√3 × √3 surface. By analyzing a number of images taken after annealing at the final temperature, we have found that the total volume of islands is several times greater than the volume which should be expected from the amount of deposited Ni. This means that Ni reacts with Ge atoms to form Ni-containing islands, perhaps the long islands and/or the hexagonal islands. The formation of the long islands indicates that the Ag/Ge (111)-√3 × √3 surfaces provide Ni, Ge, and Ni x Ge y clusters with a lower surface diffusion energy. As a result,
the formation of the long islands takes place only on the Ge(111) surface with an Ag buffer layer. Conclusions We have presented the STM results about Ni-containing nano-sized islands, as obtained on the Ge(111)-c(2 × 8) and Ag/Ge(111)-√3 × √3 surfaces after Ni deposition and annealing within the range from 470 to 770 K. On both surfaces, the appearance of defects which are typical of the whole range of annealing temperature has been observed. Apart from some types of islands, which appear on the individual surfaces, the formation Phosphoprotein phosphatase of some structures common for both studied surfaces has been recorded. We argue that the Ag layer prevents deposited Ni atoms from reacting with the Ge surfaces, at least at temperatures below 670 K. At a higher temperature, however, the formation of Ni-containing islands must be assumed in order to account for the formation of islands with a large total volume as well as the appearance of structures that are also observed on the Ni/Ge(111)-c(2 × 8) surface. Acknowledgements The financial support of the National Science Council of the Republic of China (grant no.