Defect reaction paths of nickel in float zone silicon controlled by non-equilibrium vacancies
von Philipp Saring
Datum der mündl. Prüfung:2019-03-05
Betreuer:Prof. Dr. Michael Seibt
Gutachter:Prof. Dr. Michael Seibt
Gutachter:Prof. Dr. Hans Christian Hofsäss
EnglischThis thesis investigates how defect reaction paths of nickel in float zone silicon can be controlled by non-equilibrium vacancy concentrations. Three different aspects have been studied in detail. The temperature-dependent annealing kinetics of native vacancy nitrogen complexes in float zone silicon is approached under inert conditions and vacancy detection by nickel marker experiments. The study reveals large concentrations of weakly bound vacancies that irreversibly anneal at medium temperatures. These experiments open the route to establish non-equilibrium concentrations of substitutional nickel which result in a considerably density of smaller nickel disilicide precipitates in quenching experiments. This provides evidence for an enhanced precipitate nucleation rate catalyzed by substitutional nickel. Possible nucleation stages lowering the nucleation barrier are proposed. Along these experiments special cooling conditions have been developped which promote the formation of large platelet precipitates with extraordinary aspect ratio of less than 1:1000. They form highly coherent interfaces to the silicon host lattice, which originate from a self-aligned growth process. Individual platelets have been excavated from bulk samples by Focused Ion Beam and studied in detail by Electron Beam-Induced Current analysis finding evidence of charge transport properties.
Keywords: float zone silicon; nickel; vacancies; precipitates