Heteroepitaxial Growth and Morphology of Thin Metal Films

212 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1998.In the growth of Cu and Co bilayer nanostructures, a metastable fcc alloy was observed to form despite the well-established immiscibility of Cu and Co in the relevant temperature range ∼600°C. It is established in this study that the alloy forms during the epitaxial growth of Co on Cu by a surface pump mechanism that also creates remarkable microstructures in the form of volcano-like hills and caverns. In the deposition of Co at 500°C, even on smooth flat Cu, pinholes assemble at the intersections of ripened islands which form domains of the two alternative fcc stackings, ABC &cdots; or ACB &cdots; . A driving force for alloying exists because the surface energy is reduced by 0.8 J/m2 when Cu covers Co. This free energy reduction pumps Cu from the covered Cu film, through the pinholes by surface diffusion, onto the outer surface of the Co, where it is trapped as metastable alloy by the Co flux from the evaporation source. The limited surface diffusion localizes the alloyed material close to the pinhole in a volcano-like profile. The removal of Cu leaves compact voids in the form of hexagonally facetted cavities directly beneath the volcanoes.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD