Berlin 2008 – scientific programme

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DS: Fachverband Dünne Schichten

DS 22: High-k Dielectric Materials - Synthesis, Properties, Applications

DS 22.3: Talk

Wednesday, February 27, 2008, 17:45–18:00, H 2032

From hexagonal Pr2O3 films to lattice matched twin-free PrO2/Si(111) with cubic structure — Thomas Weisemoeller, Andreas Greuling, Sebastian Gevers, Carsten Deiter, and •Joachim Wollschläger — Fachbereich Physik, Universität Osnabrück, Barbarastr. 7, 49069 Osnabrück, Germany

Praseodymiumoxide is a well suited material for epitaxial high-k films on Si due to both its high dielectric constant (k=25-30). Oxide films deposited by molecular beam epitaxy (MBE) on Si(111) have Pr2O3 stoichiometry with metastable hexagonal structure[1]. It is well known that these films can be transformed into a (less lattice matched) cubic phase by annealing at low oxygen pressure [2]. Here we present experiments performed after annealing Pr2O3 films with hexagonal structure at high oxygen pressure. The crystal structure of these films has been investigated by synchrotron based x-ray diffraction (XRD) including grazing incidence (GIXRD). The oxide films have fluorite structure which points to the formation of PrO2 with cubic structure which matches the Si lattice in all directions. The PrO2 films are exclusively B-oriented so that no twins are formed. The structure of both the oxide films and the interface has been investigated by crystal truncation rod (CTR) analysis. Depending on the preparation the oxides films show some oxygen deficiency. In addition, silicate layers are formed at the interface as verified by both XRD and x-ray reflectometry (XRR).

[1] E.J. Tarsa et al., Appl. Phys. Lett. 63 (1993) 539.

[2] T. Schroeder et al., J. Appl. Phys. 99 (2006) 014101.