Ion induced self-organized patterning of crystalline semiconductor surfaces


Ion induced self-organized patterning of crystalline semiconductor surfaces

Facsko, S.; Ou, X.; Engler, M.; Erb, D.; Hübner, R.; Škeren, T.

Low energy ion irradiation drives surfaces out of equilibrium by continuous atomic displacements in the sub-surface. At room temperature the accumulation of the created defects leads to surface amorphization and self-organized ripple patterns perpendicular or parallel to the ion beam direction are formed for incidence angles higher than 50°. At temperatures higher than the recrystallization temperature, however, all defects in the sub-surface region are dynamically annealed and the surface remains crystalline. In this regime, ion irradiation creates vacancies and ad-atoms on the crystalline surface due to sputtering and dislocations. The surfaces morphology is now determined by the kinetics of the mobile surface species. Due to the Ehrlich-Schwoebel barrier, i.e. an additional barrier for crossing terrace steps, 3D structures are created in a “reverse epitaxy” process [1].
We will present different kinds of self-organized patterns on crystalline surfaces induced by ion irradiation at elevated temperatures. Depending on the crystalline structure and the surface orientation regular patterns of inverse pyramids with three-fold, four-fold, or six-fold symmetry are observed. Furthermore, on III-V semiconductors with zinc-blende structure extremely regular periodic groove patterns with crystalline facets are produced [2].
Such periodic patterns can be used as templates for the deposition of nanostructured thin films with effective medium properties determined by the morphology, e.g. exhibiting a strong anisotropy.
[1] X. Ou, A. Keller, M. Helm, J. Fassbender, and S. Facsko, Phys. Rev. Lett. 111, 016101 (2013).
[2] X. Ou, K.-H. Heinig, R. Hübner, J. Grenzer, X. Wang, M. Helm, J. Fassbender, and S. Facsko, Nanoscale 7, 18928 (2015).

Keywords: nanopatterning; ion beam irradiation; reverse epitaxy

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