Formation and Characterization of Transversely Modulated Nanostructures in Metallic Thin Films using Epitaxial Control

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dc.contributor.advisorBruck, Hugh Aen_US
dc.contributor.authorBoyerinas, Brad Michaelen_US
dc.contributor.departmentMechanical Engineeringen_US
dc.contributor.publisherDigital Repository at the University of Marylanden_US
dc.contributor.publisherUniversity of Maryland (College Park, Md.)en_US
dc.date.accessioned2013-10-09T05:31:15Z
dc.date.available2013-10-09T05:31:15Z
dc.date.issued2013en_US
dc.description.abstractThis thesis describes a fundamental investigation into the formation, characterization, and modeling of epitaxially-controlled self-assembly at the nanoscale. The presence of coherent nanophases and the clamping effect from an epitaxial substrate enables the formation of transversely modulated nanostructures (TMNS) resulting in improved functionality, which was previously observed through increased piezoelectric response in BiFeO3. The ability to fabricate high quality epitaxial films presents opportunity to investigate coherent phase decomposition in other material systems with multifunctional response. The research herein aims to extend the concept of nanoscale self assembly in metallic systems, including Ag-Si and Pd-PdH. First, the effect of annealing a Ag-Si couple was examined, and ordered, nanoscale Ag crystallites were observed along the interface with the epitaxial Si wafer. It is demonstrated that Ag foil can be used in place of doped Ag paste (commonly used in solar cell metallization) to achieve TMNS at the interface. It was proved that annealing the Ag-Si couple in air is necessary for the self-assembly reaction to take place, as doing so prevents bulk diffusion and eutectic melting. Electron backscatter diffraction was used to verify the epitaxial relation between the Ag nanostructures and Si crystal. A method to fabricate ordered, nanoscale PdH precipitates in epitaxial Pd thin films via high temperate gas phase hydrogenation was established. Epitaxial Pd films were deposited via e-beam deposition and a V buffer layer was necessary to induce epitaxy. This novel self-assembled nanostructure may enable hysteresis-less absorption and desorption, thus improving functionality with regard to hydrogen sensing and storage. The epitaxial Pd film was characterized before and after hydrogenation with x-ray diffraction and atomic force microscopy to determine composition and nanostructure of the film. A thermodynamic model was developed to demonstrate the possibility to control or eliminate thermodynamic hysteresis via balance of elastic interaction between the coherent interfaces of metal and metal-hydride phases and the film-substrate interface. This model can be extended to other metal-hydride systems which demonstrate coherent phase decomposition.en_US
dc.identifier.urihttp://hdl.handle.net/1903/14564
dc.subject.pqcontrolledMechanical engineeringen_US
dc.subject.pqcontrolledMaterials Scienceen_US
dc.subject.pquncontrolledepitaxyen_US
dc.subject.pquncontrolledhysteresisen_US
dc.subject.pquncontrolledmetal hydrideen_US
dc.subject.pquncontrollednanostructureen_US
dc.subject.pquncontrolledphase decompositonen_US
dc.subject.pquncontrolledthin filmen_US
dc.titleFormation and Characterization of Transversely Modulated Nanostructures in Metallic Thin Films using Epitaxial Controlen_US
dc.typeDissertationen_US

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