Regensburg 2010 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 47: Topical Session Growth Kinetics III
MM 47.2: Talk
Thursday, March 25, 2010, 10:45–11:00, H4
Growth, stability and decay of cluster superlattices on the Ir(111)/graphene moiré — •Timm Gerber1, Alpha T. N’Diaye1, Carsten Busse1, Josef Mysliveček2, and Thomas Michely1 — 1II. Physikalisches Institut, Universität zu Köln — 2Charles University, Praha
The moiré pattern of graphene on Ir(111) is a versatile template for the growth of two-dimensional cluster superlattices through vapour phase deposition. Using a simple growth model and kinetic Monte Carlo simulations we find that Ir cluster superlattice formation at 350 K involves the mobility of Ir momomers and Ir dimers between different moiré unit cells. Ir clusters are epitaxial, with the (111) cluster plane aligned to the (111) substrate plane and the [110] cluster direction aligned with the [110] substrate direction. In dependence of the cluster size, upon heating cluster superlattices decay through two processes: (i) complete cluster coalescence through the migration of a cluster to a neighbouring occupied moiré unit cell, where the two clusters involved reshape to a new cluster within a single moiré unit cell; (ii) incomplete cluster coalescence or cluster sintering through two clusters fluctuating in position coming into contact. Though also in cluster sintering the clusters reshape, the new sintered cluster occupies two moiré unit cells. The decay of cluster superlattices is quantitatively modelled and estimates for activation energies are obtained. Surprisingly, for all growth and decay processes modelled, we obtain extremely low prefactors. Upon heating the height distribution of clusters may improve and reshaping of single clusters without coalescence or intercell motion is observed.