Multiscale Simulation of Laser Processing and Ablation of Semiconductor Materials

技术概述：该奖项支持激光和半导体材料光学相互作用的研究和教育。该奖项由工程学部和材料研究部的化学、生物工程、环境和运输系统联合支持。研究在共价半导体激光加工相关条件下材料与激光的相互作用。这项工作发展了预测加工条件如何影响最终材料结构的方法。这项工作包括开发和使用新的计算机模拟方法来阐明与共价半导体激光加工相关的基本物理过程。一般的方法适用于与硅相互作用的强飞秒脉冲。研究人员解决了与开发适合于远离平衡条件的热量和质量传输的多尺度模型相关的基本技术挑战。电子热输运是在连续统水平上处理的，而晶格动力学是用经典分子动力学处理的。提出的工作的一个关键组成部分是原子间的相互作用将取决于局部电子温度TE。相互作用中的参数将基于流行的Tersoff势的新修正，参数与TE的依赖关系是通过拟合有限温度从头计算的大型能量数据库建立的。这种新颖的方法将捕获已知的对亚皮秒熔化很重要的非热效应。利用受激液体的从头算模拟和Kubo-Greenwood方法解决了受激载流子的热输运问题。电子的连续描述与晶格之间的耦合将用朗之万动力学来驱动，阻尼参数拟合实验。提出的工作重点是为硅开发一个模型作为测试用例。该模型将在晶体硅激光烧蚀和非晶硅激光退火的基本物理处理中进行检验。通过与实验的对比，验证了模型的正确性，并对键弱和超快非热过程对熔化和烧蚀的作用有了新的认识。开展该项目需要研究人员解决与开发适合于远离平衡条件的热量和质量传输的多尺度模型相关的基本技术挑战。这项工作包括科学和教育两个方面。理论和计算机模拟方法将扩大研究人员对激光烧蚀的基本物理建模的能力，并将应用于晶体硅和非晶硅激光退火的技术相关过程。这项工作在培养学生技能方面具有教育价值，特别是直接参与研究和活动的毕业生和本科生，有助于招收新的研究生学习材料模拟。研究人员和学生参加研讨会活动，向学生介绍材料模拟，包括分子动力学模拟和可视化，这是与佛罗里达材料模拟协会协调的。通过材料模拟课程的开发，将教学与研究相结合。非技术概述：该奖项支持激光和半导体材料的光学相互作用的研究和教育。研究在半导体激光加工的相关条件下，材料如何与强激光束相互作用。这项工作发展了预测加工条件如何影响最终材料结构的方法。这项工作包括开发和使用新的计算机模拟方法来阐明与共价半导体激光加工相关的基本物理过程。一般方法适用于与硅相互作用的强超快激光脉冲。在实施这个项目时，研究人员将解决与开发适合于远离平衡条件的热量和质量传输的多尺度模型相关的基本技术挑战。这项工作包括科学和教育两个方面。理论和计算机模拟方法将扩大研究人员对激光烧蚀的基本物理建模的能力，并将应用于激光蚀刻硅的技术相关过程。这项工作在培养学生技能方面具有教育价值，特别是直接参与研究和活动的毕业生和本科生，有助于招收新的研究生学习材料模拟。研究人员和学生参加研讨会活动，向学生介绍材料模拟，包括计算机模拟和可视化，这是与佛罗里达材料模拟协会协调的。通过材料模拟课程的开发，将教学与研究相结合。

TECHNICAL SUMMARY:This award support research and education in optical interactions of lasers and semiconductor materials. This award is jointly supported by Chemical, Bioengineering, Environmental, and Transport Systems in the Division of Engineering and the Division of Materials Research. Research investigates how materials interact with lasers under conditions relevant to laser processing of covalent semiconductors. The work develops methods for predicting how processing conditions affect the resulting material structure. The work includes the development and use of novel computer simulation methods to elucidate the fundamental physical processes relevant to laser processing of covalent semiconductors. The general approach applies to intense femto-second pulses interacting with silicon. The researchers address the fundamental technical challenges relevant to the development of a multiscale model of heat and mass transport appropriate for far-from-equilibrium conditions. Electronic heat transport is treated at the continuum level, while the lattice dynamics are treated using classical molecular-dynamics. A crucial component of the proposed work is that the interatomic interactions will depend on the local electronic temperature TE. Parameters in the interactions will be based on a new modification of the popular Tersoff potential, with the dependence of the parameters on TE established by fitting to a large database of energies from finite-temperature ab initio calculations. This novel approach will capture nonthermal effects known to be important for sub-picosecond melting. Heat transport by excited charge carriers is addressed using ab initio simulations of excited liquids and the Kubo-Greenwood method. The coupling between the continuum description of the electrons and the lattice will be driven using Langevin dynamics with the damping parameter fit to experiment. The focus of the proposed work develops a model for silicon as a test case. The model will be tested in its treatment of the fundamental physics of laser ablation of crystalline silicon and laser annealing of amorphous silicon. Comparison to experiment is used to validate the results of the model, and produce new insight into the role of bond-weakening and ultrafast non-thermal processes to melting and ablation.Carrying out this project requires researchers to address the fundamental technical challenges relevant to the development of a multiscale model of heat and mass transport appropriate for far-from-equilibrium conditions. The effort includes both scientific and educational elements. The theoretical and computer simulation methods will expand researchers' ability to model the fundamental physics of laser ablation and will be applied to the technologically relevant processes for crystalline silicon and laser annealing of amorphous silicon. The work as educational value in developing student skills, particularly the graduates and undergraduates who are directly involved in the research and the activities aid in recruiting new students for graduate study in materials simulation. The researchers and students engage in workshop activities that introduce students to materials simulation, including molecular-dynamics simulation and visualization which is coordinated with the Florida Society for Materials Simulation. The work integrates education and research through the development of course in materials simulation.NONTECHNICAL SUMMARY:This award support research and education in optical interactions of lasers and semiconductor materials. Research investigates how materials interact with intense lasers beams under conditions relevant to laser processing of semiconductors. The work develops methods for predicting how processing conditions affect the resulting material structure. The work includes the development and use of novel computer simulation methods to elucidate the fundamental physical processes relevant to laser processing of covalent semiconductors. The general approach applies to intense ultrafast laser pulses interacting with silicon. In carrying out this project, researchers will address the fundamental technical challenges relevant to the development of a multiscale model of heat and mass transport appropriate for far-from-equilibrium conditions. The effort includes both scientific and educational elements. The theoretical and computer simulation methods will expand researchers' ability to model the fundamental physics of laser ablation and will be applied to the technologically relevant processes for laser etching of silicon. The work as educational value in developing student skills, particularly the graduates and undergraduates who are directly involved in the research and the activities aid in recruiting new students for graduate study in materials simulation. The researchers and students engage in workshop activities that introduce students to materials simulation, including computer simulation and visualization which is coordinated with the Florida Society for Materials Simulation. The work integrates education and research through the development of course in materials simulation.