Fast simulation of phase-change processes in chalcogenide alloys using a Gillespie-type cellular automata approach
Fast simulation of phase-change processes in chalcogenide alloys using a Gillespie-type cellular automata approach
复制标题
DOI：
10.1063/1.2978334
复制
发表时间：
2008-10-15
影响因子：
3.2
通讯作者：
Wright, C. David
中科院分区：
文献类型：
--
作者：
Ashwin, Peter;Patnaik, B. S. V.;Wright, C. David
提出了一种随机元胞自动机模拟器，能够在光和电存储器应用中使用的复杂退火周期期间对相变材料的结晶和非晶化行为进行时空建模。这是基于对体积能和表面能的考虑，以产生由“单体”构建的微晶的生长和衰变速率，所述“单体”本身可能是相当复杂的分子。该方法使用一个随机Gillespie型时间步进算法来处理可能发生在一个非常广泛的时间尺度上的事件。在分子长度尺度上进行模拟，并使用仅依赖于直接邻居的局部自由能变化的近似。该方法有可能跨越从头计算原子建模方法（如密度泛函理论）和大规模方法（如Johnshon-Mehl-Avrami-Kolmogorov形式主义）之间的长度尺度。作为一个例子，该模型被用来预测在相变存储器件中常用的硫属化物Ge_2Sb_2Te_5合金的结晶行为。模拟包括退火周期与非平凡的空间和时间变化的温度，在低温下的实验孵化时间，同时在较高的温度下建模非平凡的晶体尺寸分布和熔化动力学具有良好的一致性。(C)2008年美国物理研究所。[DOI 10.1063/1.2978334]
A stochastic cellular automata simulator capable of spatiotemporal modeling of the crystallization and amorphization behavior of phase-change materials during the complex annealing cycles used in optical and electrical memory applications is presented. This is based on consideration of bulk and surface energies to generate rates of growth and decay of crystallites built up from "monomers" that may themselves be quite complex molecules. The approach uses a stochastic Gillespie-type time-stepping algorithm to deal with events that may occur on a very wide range of time scales. The simulations are performed at molecular length scale and using an approximation of local free energy changes that depend only on immediate neighbors. The approach is potentially capable of spanning the length scales between ab initio atomistic modeling methods, such as density functional theory, and bulk-scale methods, such the Johnshon-Mehl-Avrami-Kolmogorov formalism. As an example the model is used to predict the crystallization behavior in the chalcogenide Ge2Sb2Te5 alloy commonly used in phase-change memory devices. The simulations include annealing cycles with nontrivial spatial and temporal variations in temperature, with good agreement to experimental incubation times at low temperatures while modeling nontrivial crystal size distributions and melting dynamics at higher temperatures. (C) 2008 American Institute of Physics. [DOI:10.1063/1.2978334]