1. Department of Electronic Systems, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway
2. Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
3. Department of Materials Science and Engineering, University of California, Davis, California 95616, USA
4. Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA