科研之友
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摘要
The initial growth of a Ag three-dimensional island on an atomically resolved Si(001) substrate was investigated in situ by scanning tunneling microscopy (STM) at room temperature. It took similar to 20 min for the island to grow from nucleation to a final dimension of 25 nm x 35 nm x 22 monolayers (ML). Uniquely, the island growth occurred under no Ag deposition. The Ag atoms required for the growth were provided from the two-dimensional Ag layer and diffusing Ag atoms on the layer that was deposited before the observation. Thanks to this unique growth mechanism, it was allowed to observe the island growth under an isotropic supply of Ag atoms without the shadowing effect of metal deposition by a scanning probe. On the other hand, the STM measurement itself affected finite effects on the growth; attractive interaction between the probe and Ag atoms promoted nucleation of the island, and tunnel current injection may have increased the effective temperature of the system. Despite such a measurement effect, some growth processes that are characteristic of typical metal thin-film growth on silicon substrates were clearly visualized, such as anisotropic and nonmonotonic growth rates that were affected by atomic surface defects, and the growth mode transition from area oriented to height oriented due to an accumulation of stress arising from the lattice mismatch.
- 出版日期2011-5-31
