勝野 喜以子

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.

成長中の固溶体の結晶組成を予測することは,結晶成長の研究における主要なテーマの1つである.結晶と母相の間の元素分配に影響を及ぼす界面カイネティックスは,多くの理論的,実験的な研究が行われたにもかかわらず,十分に理解されてはいない.本稿では,気相成長する二成分理想固溶体の成長層での原子の取り込みに必要なプロセスを明らかにすべく,モンテカルロ・シミュレーションで行った我々の最近の研究を紹介する.本シミュレーションにより,テラス(特にキンクの周辺のテラス)からの原子の離脱が成長している固溶体のバルクの組成を強くコントロールしていることが明らかになった.