1. Physik-Institut, Universität Zürich, Winterthurerstrasse
190, CH-8057 Zürich, Switzerland
2. Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
3. Institute of Condensed Matter
Physics, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
4. Department of Electrochemistry
and Conducting Polymers, Leibniz Institute of Solid State and Materials Research, Dresden, D-01069 Dresden, Germany
5. Hefei National Laboratory for
Physical Sciences at Microscale, Department of Materials Science and
Engineering, University of Science and Technology of China, 96 Jinzhai Road, Hefei 230026, China