katsuno kiiko

To explore the relaxation process of percolating labyrinthine submonolayer films, we observe in real-time the evolution of a submonolayer film with a coverage of ∼ 0.7 monolayer on SrTiO3(001) at 670 C using scanning tunneling microscopy. We find that the characteristic length begins to increase after an incubation time. During the incubation time, percolating grooves are segmented by local pinch-off events predominantly driven by thermal fluctuations. The occurrence frequency of the pinch-off events markedly decreases with an increase in the characteristic length. In the second stage, reshaping of the disconnected irregular vacancy islands occurs by edge diffusion. Finally, small vacancy islands disappear via Ostwald ripening by terrace diffusion. © 2012 Elsevier B.V. All rights reserved.

We study the dependence of the critical size of the nucleus on the density of impurity by carrying out a Monte Carlo simulation. We assume that the impurities are fixed on a crystal surface, and neglect restoration of bonds between an impurity atom and an adsorbed atom. We initially prepare one cluster in the system and investigate the change of the cluster size. When the cluster size is the critical value, the frequency of increasing the cluster size is equal to that of decreasing the size. With increasing the impurity density, the critical nucleus becomes large. When the impurity density is sufficiently high, regardless of the initial cluster size, the cluster vanishes after a long time interval, namely, the critical cluster size is diverged.

Predicting the composition of a solid solution during its growth has been one of the principal themes in the study of crystal growth. The interface kinetics, which influences the element partitioning between a crystal and mother phases, has been poorly understood in spite of many theoretical and experimental studies. In the present paper, we introduce our recent study of the Monte Carlo simulation which was applied to clarify the essential processes for the incorporation of atoms on growth layers of a binary ideal solid solution growing from its vapor. The simulation reveals that the detachment of atoms from terrace sites, especially around kink sites, strongly controls the bulk composition of a growing solid solution.