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

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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.***