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O: Fachverband Oberflächenphysik

O 18: Metallic Nanowires on Semiconductor Surfaces

O 18.8: Poster

Montag, 7. März 2016, 17:00–19:30, Poster A

Structural and electronic properties of rare-earth silicide thin films at Si(111) — •Christof Dues, Wolf Gero Schmidt, and Simone Sanna — Lehrstuhl für Theoretische Physik, Universität Paderborn, D-33095 Paderborn

Rare-earth (RE) silicides thin films on silicon surfaces are currently of high interest. They grow nearly defect-free because of the small lattice mismatch, and exhibit very low Schottky-barriers on n-type silicon. They even give rise to the self-organized formation of RE silicide nanowires on the Si(001) and vicinal surfaces.

Depending on the amount of deposited RE atoms, a plethora of reconstructions are observed for the RE silicide. While one monolayer leads to the formation of a 1× 1-reconstruction, several monolayer thick silicides crystallize in a √3 × √3 R30^∘ superstructure. Submonolayer RE deposition leads to different periodicities.

In this work we investigate the formation of RE silicides thin films on Si(111) within the density functional theory. The energetically favored adsorption site for RE adatoms is determined calculating the potential energy surface. As prototypical RE, Dysprosium is used. Additional calculations are performed for silicides formed by different RE elements. We calculate structural properties, electronic band structures and compare measured and simulated STM images. We consider different terminations for the 5 × 2 reconstruction occurring in the submonolayer regime and investigate their stability by means of ab initio thermodynamics. The same method is employed to predict the stable silicide structure as a function of the deposited RE atoms.