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。该奖项由工程部和材料研究部的化学、生物工程、环境和运输系统共同支持。研究调查材料如何在与共价半导体激光加工相关的条件下与激光相互作用。这项工作开发了预测加工条件如何影响所产生的材料结构的方法。这项工作包括开发和使用新的计算机模拟方法来阐明与激光加工共价半导体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用于远离平衡条件的热和质量传输的多尺度模型相关的基本技术挑战。电子热输运在连续介质水平上处理，而晶格动力学则用经典分子动力学处理。这项拟议工作的一个重要组成部分是原子间相互作用将取决于局域电子温度TE。相互作用中的参数将基于对流行的特尔索夫势的新修改，通过与有限温度从头计算的大型能量数据库的拟合来建立参数对TE的依赖。这种新的方法将捕捉到对亚皮秒熔化非常重要的非热效应。用激发液体的从头算模拟和Kubo-Greenwood方法研究了激发电荷载流子的热输运。电子和晶格的连续描述之间的耦合将用朗之万动力学来驱动，其阻尼参数与实验相吻合。建议的工作重点是开发一个硅模型作为测试用例。该模型将在处理晶体硅的激光烧蚀和非晶硅的激光退火的基本物理方面进行测试。通过与实验的比较，验证了模型的结果，并对键弱化和超快非热过程对熔化和烧蚀的作用提出了新的见解。实施这一项目需要研究人员解决与开发适用于远离平衡条件的多尺度热质传输模型相关的基本技术挑战。这一努力既包括科学因素，也包括教育因素。理论和计算机模拟方法将扩大研究人员模拟激光烧蚀基本物理的能力，并将应用于晶体硅的技术相关工艺和非晶硅的激光退火法。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研究生和本科生，有助于招收材料模拟研究生。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学会协调的。这项工作通过开发材料模拟课程将教育和研究结合在一起。非技术摘要：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。研究人员研究了在与半导体激光加工相关的条件下，材料如何与强激光光束相互作用。这项工作开发了预测加工条件如何影响所产生的材料结构的方法。这项工作包括开发和使用新的计算机模拟方法来阐明与激光加工共价半导体相关的基本物理过程。一般的方法适用于强超快激光脉冲与硅的相互作用。在开展这一项目时，研究人员将解决与开发适用于远离平衡条件的多尺度热和质量传输模型相关的基本技术挑战。这一努力既包括科学因素，也包括教育因素。理论和计算机模拟方法将扩大研究人员模拟激光烧蚀基本物理的能力，并将应用于激光刻蚀硅的技术相关工艺。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研究生和本科生，有助于招收材料模拟研究生。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，这是与佛罗里达州材料模拟学会协调的。通过材料模拟课程的开发，将教学与科研融为一体。

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.