Department of Physics, National Taiwan Normal University, 88, Sec, 4 Ting-Chou Rd,, Taipei 116, Taiwan.
Nanoscale Res Lett. 2013 Oct 8;8(1):416. doi: 10.1186/1556-276X-8-416.
The formation of nano-islands on both a Ge(111)-c(2 × 8) surface and an Ag/Ge(111)-(√3 × √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√7 × 2√7 or a 3 × 3 reconstruction on the Ni/Ge(111)-c(2 × 8) surface vs. islands with a 7 × 7 reconstruction on the Ni/Ag/Ge(111)-(√3 × √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)-(√3 × √3) surface are identical with those formed on the Ni/Ge(111)-c(2 × 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)-(√3 × √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 × 8) and Ag/Ge(111)-(√3 × √3) surfaces.
采用扫描隧道显微镜（STM）研究了在 Ge(111)-c(2 × 8)表面和 Ag/Ge(111)-(√3 × √3)表面上蒸发 0.1 ML Ni 形成的纳米岛。我们注意到，在温度低于 670 K 时，Ni 与各个基底表面之间的反应会形成不同的结构：在 Ni/Ge(111)-c(2 × 8)表面上形成具有 2√7 × 2√7 或 3 × 3 重构的平顶岛，而在 Ni/Ag/Ge(111)-(√3 × √3)表面上形成具有 7 × 7 重构的岛。由此我们推断，在室温到 670 K 的温度范围内，中间的 Ag 层阻碍了 Ni 和 Ge 原子之间的混合。因此，生长的岛由纯 Ni 原子组成。在 670 到 770 K 的温度范围内，在 Ag/Ge(111)-(√3 × √3)表面上生成的大多数岛与在 Ni/Ge(111)-c(2 × 8)表面上形成的岛相同，表明在 670 K 以上，Ni 原子可能与 Ge 原子结合。然而，在研究的表面的 STM 图像之间存在一个明显的区别，即在 Ni/Ag/Ge(111)-(√3 × √3)表面上出现了大的拉长岛。后者的形成可以用 Ni 在 Ge(111)-c(2 × 8)和 Ag/Ge(111)-(√3 × √3)表面上扩散的能量差异来解释。
