纳米晶柱热稳定性研究

以纳米晶柱作为表面量子点的模型,以不同截面尺寸的Al纳米晶柱为例,对其在不同温度下的弛豫过程进行了一系列分子动力学模拟,采用了Ercolessi等建立的原子镶嵌势计算原子间的相互作用力.结果表明:对于沿相互垂直的{110}和{211}面切割形成的近正方形截面晶柱.其截面厚度存在一热稳定性转变临界值.小于该值时纳米晶柱迅速失稳,发生熔融-重结晶的过程;大于该值时只发生缓慢的表面原子迁移重组.两种情况下形成的稳定结构均为由{111}和{100}面组成的正多面体纳米岛,只是两种面的相对面积比有所不同;该临界尺寸随温度升高而呈近线性增大.模拟结果还显示,纳米晶柱的高度对其稳定性没有明显影响.

A Study on Thermal Stability of Nanocrystalline Pillars

Using nanocrystalline pillars as models of surface quantum dots, and Al nanocrystalline pillar as example, the relaxation processes of the pillars with different sizes at different temperatures have been simulated by molecular dynamics. An EAM potential developed by Ercolessi was used to calculate the inter-atomic forces. The results show that, for nanocrystalline pillars with near-square cross section and with {110} and {211} planes as side surfaces, there exists a critical size for stability transition. The nano-pillars with thickness lower than the critical size melted quickly and then recrystallized, while those with thickness larger than the critical size will be slowly reconstructed by surface migration of atoms. The reconstructed stable structures, through either the melt-recrystallization or surface migration, are polyhedrons consisting of {111} and {100} surfaces with different ratios of the areas. The critical size increases linearly with raising temperature. The simulations also show that the stability of the nanocrystalline pillars is insensitive to their height.