STM'06/Nano9 - Int'l Conference on Nanoscience and Technology, Basel, Switzerland, 7/30 - 8/4/2006 (poster)

Growth of 2D Ordered Nanocluster Arrays via Threading Dislocation Pair Annihilation

Bogdan Diaconescu, Georgi Nenchev, and Karsten Pohl

Strained metallic interfaces can lead to highly ordered misfit dislocation networks that can be used as patterned substrates for growth of clusters with specific size and densities. The great potential of this natural templating method is that the characteristic feature sizes and densities are predicted to depend on the interfacial stress in these strained layers.1,2 The bottom-up approach of growing nanostructured ordered arrays of clusters on the misfit dislocation networks of strained metallic thin films requires a detailed understanding of the nucleation and film-adsorbate interaction processes. In the case of sulfur adsorption on submonolayer silver films on the 0001 surface of ruthenium, the Ag’s short herring bone rectangular misfit dislocation unit cell of 54Å x 40Å (19 x 16 Ag atoms) reconstructs into a well-ordered triangular array of S filled vacancy islands 50Å apart.

Atomically resolved measurements from our new home-built variable-temperature scanning tunneling microscope reveal that the S cluster growth mechanism involves a local restructuring of the misfit dislocation network of Ag with the final structure free of threading dislocations. Adsorbed S atoms will preferably bind on the Ru substrate thus displacing Ag atoms and creating two-dimensional S filled Ag vacancy islands. The new symmetry and morphology of the composed S/Ag/Ru(0001) films is obtained via a threading dislocation annihilation mechanism where adjacent and opposite pairs of threading dislocations are replaced by the S filled Ag vacancy islands. The local character of the annihilation process is shown by the conservation of the unit cell size area of 21.5nm2.
Supported by NSF-CAREER-DMR-0134933 and ACS-PRF-37999-G5.

1 K. Pohl et al., Nature 397, 238 (1999)
2 K. Thürmer et al., Science 311, 1272 (2006)