M. Rusanen

Morphology of ledge patterns during step flow growth of metal surfaces vicinal to fcc(001)

The morphological development of step edge patterns in the presence of meandering instability during step flow growth is studied by simulations and numerical integration of a continuum model. It is demonstrated that the kink Ehrlich-Schwoebel barrier responsible for the instability leads to an invariant shape of the step profiles. The step morphologies change with increasing coverage from a somewhat triangular shape to a more flat, invariant steady state form. The average pattern shape extracted from the simulations is shown to he in good agreement with that obtained from numerical integration of the continuum theory.

Kinetic Monte Carlo simulations of oscillatory shape evolution for electromigration-driven islands

The shape evolution of two-dimensional islands under electromigration-driven periphery diffusion is studied by kinetic Monte Carlo (KMC) simulations and continuum theory. The energetics of the KMC model is adapted to the Cu(100) surface, and the continuum model is matched to the KMC model by a suitably parametrized choice of the orientation-dependent step stiffness and step atom mobility. At 700 K shape oscillations predicted by continuum theory are quantitatively verified by the KMC simulations, while at 500 K qualitative differences between the two modeling approaches are found.

Evolution of Cu nanoclusters on Cu(100)

Usin gm olecular dynamics simulations combined with kinetic Monte Carlo methods we have studied the evolution of copper nanoclusters on a copper (100) surface. We have developed a method for relaxing the clusters into a suitable configuration for input into the kinetic Monte Carlo method using molecular dynamics. Using kinetic Monte Carlo methods we have simulated the evolution of clusters with sizes of 22–2045 atoms at temperatures of 220–1020 K. We found that the Cu clusters on the surface will be reduced to one monolayer if given enough time to relax, and that this process shows an Arrhenius behaviour. In this paper we present the relaxation method that we developed and our observations for the evolution of the clusters. (Some figures in this article are in colour only in the electronic version)

Instability and Wavelength Selection during Step Flow Growth of Metal Surfaces Vicinal to fcc(001)

We study the onset and development of ledge instabilities during growth of vicinal metal surfaces using kinetic Monte Carlo simulations. We observe the formation of periodic patterns at [110] close packed step edges on surfaces vicinal to fcc(001) under realistic molecular beam epitaxy conditions. The corresponding wavelength and its temperature dependence are studied in detail. Simulations suggest that the ledge instability on fcc(1,1,m) vicinal surfaces is controlled by the strong kink Ehrlich-Schwoebel barrier, with the wavelength determined by dimer nucleation at the step edge. Our results are in agreement with recent continuum theoretical predictions, and experiments on Cu(1,1,17) vicinal surfaces.

Meandering instability of curved step edges on growth of a crystalline cone

Abstract We study the meandering instability during growth of an isolated nanostructure, a crystalline cone, consisting of concentric circular steps. The onset of the instability is studied analytically within the framework of the standard Burton–Cabrera–Frank model, which is applied to describe step flow growth in circular geometry. We derive the correction to the most unstable wavelength and show that in general it depends on the curvature in a complicated way. Only in the asymptotic limit where the curvature approaches zero the results are shown to reduce to the rectangular case. The results obtained here are of importance in estimating growth regimes for stable nanostructures against step meandering.

Modelling Size-Selected Growth of Nanodots by Using Reaction Kinetic Approach

The size selection of nanodots during the growth is modelled by using the reaction kinetic model with reaction rates for dot size dependent attachment and detachment processes, related to the free energy of dots. Long-lived metastable state is found near the minimum of free energy, but the kinetics of the growth causes the peak to overshoot the location of minimum of the energy. The size distribution of dots is shown to be nearly Gaussian with minor skewness originated from kinetics. However, it is argued that this skewness is inherently related to the effect of overshooting, and thus to the formation of the long lived metastable state with size selected nanodots. Based on RKM, a simple continuum model is derived to describe the size selection and narrowing of the size distribution.