Multiscale Simulation of Cluster Growth and Deposition Processes by Direct Simulation Monte Carlo Method

团簇沉积膜的特性受飞行过程中团簇制备方法的影响，相关的物理尺度可达厘米级。此外，由于衬底上的偏析过程的行为是不可忽略的，最小的物理尺度是10 nm的量级。虽然这个多尺度问题的完整分析是非常困难的，它提供了一个典型的研究课题，在一个复杂的系统的动力学组成的相互作用的子系统具有非常不同的尺度。本文介绍了一种新的基于直接模拟蒙特卡罗（DSMC）和蒙特卡罗（MC）方法相结合的团簇生长和沉积过程的模型，以研究实验条件对团簇生长和沉积过程的影响。从宏观角度出发，模拟了不同实验条件下团簇和惰性气体在飞行轨迹中的行为。利用该模型得到了不同条件下生成的团簇的几种尺寸分布。此外，这些团簇的沉积过程中，通过一个简单的模型来计算，以估计通过团簇沉积获得的这种纳米结构的形貌。在这个模型中，我们假设沉积团簇是由两个元素和偏析的沉积团簇发生的两个不混溶元素之间的能隙。模拟的结果表明，尺寸分布与实验条件密切相关，反过来又对薄膜性能产生重大影响。

Cluster deposited film's features are influenced by the production method of cluster during the flight path, the relevant physical scale to be studied is as large as centimeters. Moreover, since the behavior of segregation processes on the substrate is not negligible, the smallest physical scale is of the order of 10 nm. Although a complete analysis of this multiscale problem is extremely difficult, it provides a typical research subject in the dynamics of a complex system consisting of interacting subsystems with very different scales. In this paper a new model of cluster growth and deposition processes based on a combination of Direct Simulation Monte Carlo (DSMC) and Monte Carlo (MC) methods is introduced to examine the effects of experimental conditions on cluster growth and deposition processes. From the macroscopic viewpoint, we simulate the behavior of clusters and inert gas in the flight path under different experimental conditions. Several types of size distributions of generated clusters under various conditions are obtained by the present model. Moreover, the deposition process of these clusters is calculated by a simple model to estimate a morphologies of this nanostructures obtained by cluster deposition. In this model we assume that the deposited clusters are composed of two elements and segregation of deposited clusters occurred from energy gaps between two immiscible elements. The results of the simulations reveal that the size distribution is strongly related to the experimental conditions and in turn has a major effect on the film properties.