Article

Nickel-containing nano-sized islands grown on Ge(111)-c(2 × 8) and Ag/Ge(111)-(√3 × √3) surfaces

Nanoscale Research Letters (Impact Factor: 2.78). 10/2013; 8(1):416. DOI: 10.1186/1556-276X-8-416
Source: PubMed

ABSTRACT

The formation of nano-islands on both a Ge(111)-c(2 x 8) surface and an Ag/Ge(111)-([square root]3 x [square root]3) surface evaporated with 0.1 ML Ni was investigated by scanning tunneling microscopy (STM). We have noticed that at temperatures lower than 670 K, the reaction between Ni and the individual substrate surfaces proceeds to form different structures: flat-topped islands with a 2[square root]7 x 2[square root]7 or a 3 x 3 reconstruction on the Ni/Ge(111)-c(2 x 8) surface vs. islands with a 7 x 7 reconstruction on the Ni/Ag/Ge(111)-([square root]3 x [square root]3) surface. From this we have inferred that within a temperature range between room temperature and 670 K, the intermediate Ag layer retards mixing between Ni and Ge atoms. As a result, the grown islands are composed of pure Ni atoms. Within a temperature range from 670 to 770 K, most islands produced on the Ag/Ge(111)-([square root]3 x [square root]3) surface are identical with those formed on the Ni/Ge(111)-c(2 x 8) surface, suggesting that above 670 K, Ni atoms are likely to bind with Ge atoms. However, an essential difference between STM images of the surfaces under study exists in the appearance of large elongated islands on the Ni/Ag/Ge(111)-([square root]3 x [square root]3) surface. The formation of the latter is explained in terms of a difference in energy for Ni diffusion on the Ge(111)-c(2 x 8) and Ag/Ge(111)-([square root]3 x [square root]3) surfaces.

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