Stress and Structure Evolution During Formation of Polycrystalline Metallic Films: From Adatoms to Coalescence

这笔拨款探索了对薄膜形成过程中涉及的原子过程的清楚理解。新的应力测量能力允许研究吸附原子与衬底的相互作用，以及亚单分子层区域中的吸附原子与吸附原子的相互作用。这项研究的目的是将生长过程中和生长中断期间的应力演变的原位测量与非原位扫描隧道显微镜、非原位透射电子显微镜以及结构演变的原位透射电子显微镜观察相关联。将进行外延生长和多晶薄膜生长的实验。将使用分子动力学和从头计算方法来模拟吸附原子群体的详细影响。模拟结果将与外延系统中的实测力进行比较。通过这些研究，将确定改变吸附原子浓度和团簇形成的单独影响。对生长后期的实验研究将允许对团簇粗化、生长和合并的影响进行单独表征。应力演化的测量与结构演化的研究相结合，将为原位实时动力学分析薄膜形成的早期阶段所涉及的各种原子过程提供强大的工具。该研究将在包括微电子、纳米磁性以及微和纳米机电系统在内的广泛的微和纳米器件和系统中得到应用，其中纳米晶金属结构的性能、性能和可靠性受到其应力状态和缺陷结构的强烈影响。这项研究和相关研究的成果将通过母机构内的各种研究生和本科课程以及通过与其他大学的伙伴关系和专业工程师暑期课程传播。这项研究将与麻省理工学院和新加坡的合作者一起进行，并将间接支持相关教职员工研究小组的研究活动。研究成果将通过出版物和演示文稿以及互联网传播，并将纳入工程师直接使用的软件工具。*

The grant explores a clear understanding of the atomic processes involved in film formation. New stress measurement capabilities allow studies of adatom-substrate interactions, as well as adatom-adatom interactions in the sub-monolayer regime. An objective of the proposed study is to correlate in-situ measurements of stress evolution during growth and during growth interruptions with ex-situ STM, ex-situ TEM, and in-situ TEM observations of structure evolution. Experiments involving both epitaxial and polycrystalline film growth will be conducted. Detailed effects of populations of adatoms will be simulated using molecular dynamics and ab-initio approaches. Simulation results will be compared with measured forces in epitaxial systems. Through these studies, the separate effects of changing adatom concentrations and cluster formation will be determined. Experimental studies of later stages of growth will allow separate characterization of the effects of cluster coarsening, growth, and coalescence. Measurements of stress evolution, when correlated with studies of structure evolution, will provide a powerful tool for in-situ real-time kinetic analyses of the various atomistic processes involved in the earliest stages of film formation.%%%The study will have applications in a wide array of micro and nano-devices and systems including microelectronic, nanomagnetic, and micro- and nanoelectromechanical systems where the properties, performance, and reliability of nanocrystalline metallic structures are strongly affected by their stress state and defect structures. Results from this and related studies will be disseminated through a variety of graduate and undergraduate courses within the parent institution, as well as through partnerships with other universities and through summer courses for professional engineers. The research will be carried out with collaborators at MIT and in Singapore, and will indirectly support the research activities of the research groups of the faculty involved. Research results will be disseminated through publications and presentations, as well as via the Internet, and will be incorporated in software tools that are used directly by engineers.***