Interplay of strain relaxation and chemically induced diffusion barriers: Nanostructure formation in 2D alloys
详细信息 查看全文
- 作者：Volkmann ; T. ; Much ; F. ; Biehl ; M. ; Kotrla ; M.
- 关键词：Non-equilibrium thermodynamics and statistical mechanics ; Monte Carlo simulations ; Self-assembly ; Epitaxy ; Alloys
- 刊名：Surface Science
- 出版年：2005
- 出版时间：July 20, 2005
- 年：2005
- 卷：586
- 期：1-3
- 页码：157-173
- 全文大小：552 K
文摘
We study the formation of nanostructures with alternating stripes composed of bulk-immiscible adsorbates during submonolayer heteroepitaxy. We evaluate the influence of two mechanisms considered in the literature: (i) strain relaxation by alternating arrangement of the adsorbate species and (ii) kinetic segregation due to chemically induced diffusion barriers. A model ternary system of two adsorbates with opposite misfit relative to the substrate, and symmetric binding is investigated by off-lattice as well as lattice kinetic Monte Carlo simulations. We find that neither of the mechanisms (i) or (ii) alone can account for known experimental observations. Rather, a combination of both is needed. We present an off-lattice model which allows for a qualitative reproduction of stripe patterns as well as island ramification in agreement with recent experimental observations for CoAg/Ru(0 0 0 1) [R.Q. Hwang, Phys. Rev. Lett. 76 (1996) 4757]. The quantitative dependencies of stripe width and degree of island ramification on the misfit and interaction strength between the two adsorbate types are presented. Attempts to capture essential features in a simplified lattice gas model show that a detailed incorporation of non-local effects is required.