Physical mechanism behind mediation epitaxy

Several growth schemes have been successful in producing thin single crystal epitaxial CoSi₂ films on the Si(100) surface. However, the underlying physics of the film growth have not been quantified or understood. In this study we have chosen the oxide mediated epitaxy of CoSi₂ on Si(100) as a model system to examine mediated epitaxy methods. With the use of a modified in-situ ultra-high vacuum transmission electron microscope we have collected qualitative and quantitative data concerning the phase sequence, nucleation behavior and film growth rates during the reaction. Using this data we determined that the epitaxial formation of a CoSi ₂ film is due to a minimization of the surface free energy of the thin, platelet-like islands of CoSi₂ that form with oxide mediated epitaxy. The oxide layer promotes the growth of the thin CoSi₂ islands by limiting the Co concentration at the Si surface but also allowing the Co to reach the Si surface at relatively low reaction temperatures. We also discuss the unique nucleation and growth of the CoSi₂ islands in this system.