Island shapes, island densities, and stacking-fault formation onIr(111): Kinetic Monte Carlo simulations and experiments

Abstract

Submonolayer homoepitaxy on Ir͑111͒ is studied by a refined kinetic lattice Monte Carlo ͑KLMC͒ model and compared to results obtained from scanning tunneling microscopy experiments. The KLMC model not only considers individual atomic jumps on regular and stacking-fault sites, but also describes the cooperative motion of small adatom clusters, which determines the temperature-dependent probability of stacking-fault island formation. A complete catalog of diffusion processes at island edges is included that allows one to model the variations of island shapes with temperature. By taking input parameters for cluster and edge diffusion from experiments, calculated island densities as well as the probability of stacking-fault formation agree very well with experimental results for different temperatures. The comparison of simulated and experimental island shapes, however, reveals obvious differences. After systematic modifications of the event database for edge diffusion processes, all features of island shape evolution are well reproduced.

Diffusion of small two-dimensional Cu islands on Cu(111) studied with a kinetic Monte Carlo method

“…Recent theoretical studies of the energetics and dynamics of 1-7 atom Cu islands on Cu͑111͒ have once again highlighted the role of the concerted motion of the island in controlling its diffusion characteristics. 28 In the very recent work of Mueller et al 16 good agreement with experimental data on submonolayer epitaxy on Ir͑111͒ is also obtained with the inclusion of concerted motion of islands ͑with the stacking fault sites͒. Issues about the relative importance of the proposed diffusion mechanisms, the relevance of the occupation of the hcp sites, and the observed anomalous diffusion for certain sizes, are striking aspects of the diffusion of small 2D islands on fcc͑111͒ surfaces and may control the subsequent growth patterns on these surfaces.…”

“…Motivated by experimental observations, initially using field ion microscopy ͑FIM͒, 1-6 and more recently with the use of the scanning tunneling microscope ͑STM͒, 7-15 the study of adatom and vacancy island diffusion as a function of size has been an important concern also for many theorists [16][17][18][19][20][21][22][23][24][25] Because of the inherent differences in the microscopic processes responsible for the diffusion and its scaling behavior with size, the discussion has naturally bifurcated into those for the larger islands, usually containing more than 20 atoms, and the smaller ones ͑N Ͻ 20͒. For the larger islands, the diffusion coefficients appear to scale as a function of the size and the scaling exponent is expected to reflect the intervening atomistic processes responsible for the diffusion.…”

Formation and morphological evolution of self-similar 3D nanostructures on weakly interacting substrates

“…The explicit inclusion of hcp adsorption sites in KMC simulations has previously been used to study stacking-fault nucleation [56,58] and grain-boundary propagation [59] in Ir(111), and is referred to as providing a refined lattice. Here, a refined lattice is used to describe the different atomistic geometries that adatoms encounter as they diffuse along, and across, the two sets of step edges that exist on fcc(111) island surfaces-commonly referred to as A [ (100) (Fig.…”

Self-learning kinetic Monte Carlo simulations of self-diffusion of small Ag islands on the Ag(111) surface

“…Therefore a great deal of effort has been devoted towards the Self-diffusion of single atom and clusters on metal surfaces 3 both theoretically and experimentally [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] . There has also been both experimental and theoretical efforts to find the activation barriers and prefactors for adatom diffusion process [19][20][21][22][23][24][25][26][27][28][29][30][31] on various surfaces.…”