2D island shape
(rus. островков (двумерных), форма)
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islands may have different shapes depending on their growth conditions. Morphologically, two broad classes of islands are distinguished: 1) ramified islands, i.e. islands with a dendritic fractal structure that have rough edges; 2) compact islands shaped as domed polygons with relatively straight and equiaxial edges.
Description
The compactness of an island depends largely on the capability of a trapped atom to migrate along the island’s edge and cross its corners. Ramified islands are formed when the diffusion of atoms along their edges occurs quite slowly. In an extreme case (so-called hit-and-stick mode), an atom will stick to an island and remain fixed in that position, creating an island with a thickness of branches in the order of one atom. When an atom can move along the edge of an island but cannot cross its corner, a ramified island is formed, but has thicker walls. When atoms can easily cross corners, compact islands develop. The change of island growth mode from fractal to compact occurs when the temperature grows. For example, this change occurs for Pt islands on the surface of Pt(111) [2] at temperatures ranging between 300 and 400 k (see fig.).
Illustrations
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Influence of temperature on the shape of islands during homoepitaxy growth of Pt on Pt(111): right microphotograph — compact triangular islands grow at 400 К; left microphotograph — growth process at 300 K results in development of dendritic islands. Authors: M. Bott, T. Michely, G. Comsa, Surface and Vacuum Physics Research Institute, Jülich, Germany [2]. |
Authors
- Zotov Andrey V.
- Saranin Alexander A.
Sources
- Oura K. et al. Surface Science: An Introduction // Springer, 2010 - 452 pp.
- Bott M., Michely T., Comsa G. The homoepitaxial growth of Pt on Pt(111) studied with STM // Surface Science. 1992. V. 272, №1. P. 161–166.