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Temperature-dependent 2D-3D growth transition of ultra-thin Pt films deposited by PLD

During the growth of metal thin films on dielectric substrates at a given deposition temperature T, the film's morphology is conditioned by the magnitude and asymmetry of up- and downhill diffusion. Any severe change of this mechanism leads to a growth instability, which induces an alteration of the thin film morphology. In order to study this mechanism, ultra-thin Pt films were deposited via pulsed laser deposition (PLD) onto yttria-stabilized-zirconia single crystals at different deposition temperatures. The morphological evolution of Pt thin films has been investigated by means of scanning electron microscopy (SEM), atomic force microscopy (AFM) and standard image analysis techniques. The experimentally obtained morphologies are compared to simulated thin film structures resulting from a two-dimensional kinetic Monte Carlo (KMC) approach. Two main observations have been made: i) Thin Pt films deposited onto zirconia undergo a growth transition from two-dimensional to three-dimensional growth at T > 573 K. The growth transition and related morphological changes are a function of the deposition temperature. ii) A critical cluster size of i\ast = 4 in combination with an asymmetric Ehrlich-Schwoebel (ES) barrier favoring the uphill diffusion of atoms allows for a computational reproduction of the experimentally obtained film morphologies.