1. Helmholtz-Zentrum Berlin für Materialien und Energie Institute, Functional Oxides for Energy Efficient Information Technology, Hahn-Meitner Platz 1, 14109 Berlin, Germany
2. Oak Ridge National Laboratory, Center for Nanophase Materials Sciences, 1 Bethel Valley Rd., Oak Ridge, Tennessee 37831-6487, United States
3. Freie Universität Berlin, Physical Chemistry, Arnimallee 22, Berlin 14195, Germany