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首页> 外文期刊>Physical review. B, Condensed Matter And Materials Physics >Nucleation and growth of Ag islands on fivefold Al-Pd-Mn quasicrystal surfaces: Dependence of island density on temperature and flux
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Nucleation and growth of Ag islands on fivefold Al-Pd-Mn quasicrystal surfaces: Dependence of island density on temperature and flux

机译：五重Al-Pd-Mn准晶体表面上银岛的成核和生长：岛密度与温度和通量的关系

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摘要

Scanning tunneling microscopy (STM) has been used to investigate the nucleation and growth of Ag islands on the fivefold surface of an icosahedral Al-Pd-Mn quasicrystal. Analysis of the data as a function of deposition temperature, from 127 K to 300 K, reveals that island density is constant, while at higher temperature it decreases. To model this behavior, we first show that the potential energy surface describing bonding of Ag at various locations on the surface is complex, with a few sites acting as traps for clusters of adatoms. We then develop a rate equation model which incorporates enhanced nucleation at trap sites relative to nucleation at regular sites on terraces. It recovers the temperature dependence of the island density, plus previous flux-scaling data. Our model suggests that the critical size for both types of nucleation sites is large—corresponding to stable clusters of at least 6 Ag atoms—and that binding between atoms at trap sites is significantly stronger than at free terrace sites. The data and the model, combined, provide guidance about the conditions of temperature and flux under which saturation of trap sites can be expected. This, in turn, provides a general indicator of the conditions that may favor localized pseudomorphic growth at low coverage, here and in other systems.
机译：扫描隧道显微镜（STM）已用于研究二十面体Al-Pd-Mn准晶体的五倍表面上Ag岛的形核和生长。分析数据作为沉积温度（从127 K到300 K）的函数，表明岛密度是恒定的，而在较高温度下，岛密度会减小。为了对这种行为进行建模，我们首先表明，描述表面上各个位置上的Ag结合的势能表面很复杂，其中一些位点充当吸附原子簇的陷阱。然后，我们开发一个速率方程模型，该模型结合了陷阱位置相对于梯田常规位置上的成核作用增强的成核作用。它恢复了岛密度对温度的依赖性，以及先前的磁通缩放数据。我们的模型表明，两种成核位点的临界尺寸都很大-对应于至少6个Ag原子的稳定簇-并且陷阱位点处的原子之间的结合明显强于自由平台位点处。数据和模型相结合，可提供有关温度和通量条件的指导，在这些条件下可以预期阱位的饱和。反过来，这提供了条件的一般指标，这些条件可能有利于此处和其他系统中低覆盖率下的局部拟晶生长。

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