Evolution of Nanoscale Film Morphology

本研究项目的目标是对金属和半导体表面薄膜形貌的演变进行多尺度的计算和理论研究。这项研究涉及几种纳米尺度的模拟策略：(1)利用密度泛函理论和量子化学方法，对能量、电子效应、扩散路径和选定的吸附振动模式进行小规模体系的从头算电子结构计算；(2)根据所提出的从头计算结果和实验数据的参数化，建立稳健的模型势；(3)应用最近开发的加速MD程序来研究在微米秒内进行模拟时可能出现的新的团簇扩散过程；(4)依次确定所提议的衬底上小Ag团簇的振动动力学、热力学、扩散前置因子和速率；(5)用模型势计算了银团簇在所建议衬底上的势垒和扩散路径；(6)用计算的扩散速率和动力学蒙特卡罗技术中的能量学对实际系统尺寸(微米)的外延生长进行了模拟；(7)利用上述信息对纳米结构弛豫进行了连续模拟。一个额外的策略是与正在进行的实验相结合，提供持续的反馈。这是化学工程、物理、化学和数学研究人员共同努力的结果。与工业合作一起，该项目将使他们能够确定系统的长度和时间尺度的特征，这些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.