Oxygen exchange and transport in thin zirconia films on Si(100)

The composition and atomic depth distributions of ultrathin zirconia films (∼30 Å) deposited on Si(100) have been investigated using medium-energy ion scattering (MEIS). Reoxidation in ¹⁸O₂ permits the oxygen incorporation, exchange, and mobility to be followed due to the isotope sensitivity of the MEIS technique. These quantitative studies showed that significant interfacial SiO₂ growth results when reoxidizing samples at temperatures as low as 500 °C, and that this growth saturates in time and pressure but increases with temperature. Substantial isotope exchange was also observed under various experimental conditions. The results are discussed taking into account published data on the bulk and grain boundary diffusion of O in monoclinic and tetragonal zirconia, the diffusivity of O in SiO₂, and the nanocrystallinity of the films.