Evolution of Nanoscale Film Morphology

摘要本研究项目的目的是对金属和半导体表面薄膜形态的演变进行多尺度的计算和理论研究。本研究涉及几种纳米尺度的建模策略：(1)利用密度泛函理论和量子化学方法计算小尺度系统的电子结构，包括能量学、电子效应、扩散路径和选择的吸附质振动模式；(2)从初始计算和实验数据的参数化结果中开发鲁棒模型势；(3)应用最近开发的加速MD代码来检查在进行微毫秒模拟时可能出现的新型簇扩散过程；(4)依次测定了在提议的衬底上的小Ag团簇的振动动力学、热力学、扩散前因子和速率；(5)利用模型电位计算银团簇在基体上的能垒和扩散路径；(6)利用计算的扩散速率和动力学蒙特卡罗技术模拟实际系统尺寸（微米）的外延生长；(7)利用以上信息建立纳米结构松弛的连续体模型。另一个策略是与正在进行的实验一起工作，以提供持续的反馈。这是化学工程、物理、化学和数学研究人员的合作成果。与工业合作一起，该项目将允许他们确定系统的长度和时间尺度的特征，这些长度和时间尺度比最初收集信息的原子尺度大几个数量级。

ABSTRACTThe goal of this research project is to conduct a multi-scale computational and theoretical investigation of the evolution of thin film morphology on metal and semi-conductor surfaces. This research involves several nanoscale modeling strategies: (1) ab inito electronic structure calculations for small-scale systems using density functional theory and quantum chemistry approaches for energetics, electronic effects, diffusion paths, and selected adsorbate vibrational modes; (2) development of robust model potentials from parameterization of results from the proposed ab initio calculations and experimental data; (3) application of recently developed accelerated MD code to examine novel cluster diffusion process which may appear when simulations are performed for micro-mili seconds; (4) determination, successively, of the vibrational dynamics, thermodynamics, diffusion prefactors and rates for small Ag clusters on proposed substrates; (5) calculation of energy barriers and diffusion paths for Ag clusters on proposed substrates using the model potentials; (6) modeling of epitaxial growth for realistic system sizes (microns) using the calculated diffusion rates an energetics in kinetic Monte Carlo technique; (7) continuum modeling of nanostructure relaxation using information from all of the above. An added strategy is to work in tandem with on-going experiments to provide constant feedback.This is a collaborative effort by researchers in chemical engineering, physics, chemistry and mathematics. Together with industrial collaboration, the project will allow them to determine the characteristics of the systems for length and time scales that are several orders of magnitude larger than the atomic scales for which the information is initially collected.