Dresden 2009 – scientific programme

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DS: Fachverband Dünne Schichten

DS 11: Layer Growth: Evolution of Structure and Simulation

DS 11.2: Talk

Tuesday, March 24, 2009, 14:15–14:30, GER 37

Stacking fault suppression in ion assisted growth of Ir on Ir(111) — •Sebastian Bleikamp and Thomas Michely — Institute of Physics 2, University of Cologne, Germany

Due to their low energy, stacking faults are among the most frequent defects in thin films.

In homoepitaxy of Ir on Ir(111) around room temperature, stacking faults are formed in large numbers, which propagate through the growing film, causing extended defect structures. Eventually thin Ir films become heavily twinned and grow rough due to the twin associated defects.

Here we present kinetic strategies for the avoidance of stacking fault propagation and defect structure formation based on ion assistance. Ir is evaporated with ion assistance of 100eV Ar⁺ ions at normal incidence with an ion to atom arrival ratio of R=1:2 or with ion assistance of 500eV Ar⁺ ions incident at an angle of 85^∘ with respect to the surface normal with R=1:10. Based on scanning tunneling microscopy investigations we find that this treatment transfers the growth mode to layer-by-layer growth and no twin crystallites are formed. The result is backed up by low energy electron diffraction measurements. Annealing shows that a significant amount of noble gas is incorporated in the films during growth. Gas incorporation could be avoided if the necessary energy could be supplied to the Ir atoms themselves.

Analysis of the atomic processes involved indicates that the key action of the ions is to destroy the defect structures stabilizing the faults, rather than to suppress fault nucleation.