The characteristics of heterogeneous nucleation on concave surfaces and implications for directed nucleation or surface activity by surface nanopatterning

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• 作者：M. Qian ; J. Ma
• 关键词：A1. Nucleation ; A1. Surfaces ; A1. Surface structure ; A1. Surface processes ; A1. Roughening
• 刊名：Journal of Crystal Growth
• 出版年：2012
• 出版时间：15 September, 2012
• 年：2012
• 卷：355
• 期：1
• 页码：73-77
• 全文大小：543 K

文摘

The characteristics of heterogeneous nucleation on concave spherical surfaces were analysed using a novel analytical approach and compared with nucleation on both convex and planar surfaces. The complex expressions of (: free energy change and r: embryo radius) for nucleation on concave spherical surfaces can be reduced to the simple form for nucleation on planar surfaces by introducing an appropriate pseudo-contact angle, providing a new fundamental link. The advantages of heterogeneous nucleation on a concave spherical surface of radius R over a planar surface occur primarily when 2R<10r? (r*: nucleus radius) and diminish rapidly when 2R>10r*. This is similar to nucleation on convex spherical surfaces, where the disadvantages of nucleation over a planar surface occur primarily when 2R<10r* and diminish rapidly when 2R>10r*. The substrate size 10r* thus provides an approximate borderline that distinguishes between curved and planar surfaces for nucleation. The advantages or disadvantages of nucleation over a planar surface are most outstanding when the concave (advantageous) or convex (disadvantageous) surface shows a specific contact angle with the nucleus. The nanoscale nature of the threshold size 10r* presents a clear fundamental support to surface nanopatterning for directed nucleation. A minimum depth is required for a nanoscale crater to be a favourable nucleation site.