Regensburg 2013 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
O: Fachverband Oberflächenphysik
O 79: Oxide Surfaces III
O 79.6: Vortrag
Donnerstag, 14. März 2013, 17:15–17:30, H45
Characterization of thin cerium oxide films on Cl/Si(111) studied by GIXRD and XPS — •Jan Höcker1, Björn Kaemena1, Florian Bertram2, Jan Ingo Flege1, and Jens Falta1 — 1Institute of Solid State Physics, University of Bremen, 28359 Bremen — 2Hamburger Synchrotronstrahlungslabor am Deutschen Elektronensynchrotron, 22607 Hamburg
Cerium oxide is of strong interest in today’s research because of its catalytic properties as well as its potential application in microelectronics, e.g., as an epitaxial high-k gate oxide on Si. As known from previous studies of ultrathin cerium oxide films on Si(111) (cf. Flege et al., PRB 84, 2011), Cl-passivation facilitates epitaxial growth of the sesquioxide Ce2O3 phase and suppresses amorphous interface formation.
We have investigated the structural and chemical composition of 3 - 18 nm thin cerium oxide films grown by reactive MBE on either clean or Cl-passivated Si(111) by ex-situ grazing-incidence x-ray diffraction (GIXRD) and x-ray photoelectron spectroscopy (XPS). Only for Cl-passivated substrates reciprocal space mapping reveals well ordered oxide films. Capped samples show a dioxide fluorite (Ce4+) as well as a sesquioxide bixbyite (Ce3+) phase in contrast to uncapped samples, which only show a dioxide phase. XPS confirms a larger Ce4+ proportion for passivated substrates after exposure to ambient conditions whereas a mixture of Ce3+ and Ce4+ in the non-passivated case is observable. We conclude that only on passivated Si(111) a metastable Ce2O3 film crystallizes, which is converted into a well ordered dioxide phase under ambient conditions.