1. Department of Electronics and Nanoengineering, Micronova, Aalto University, P.O. Box 13500, FI-00076 Aalto, Finland
2. Department of Applied Physics, Aalto University School of Science, P.O. Box 15100, FI-00076 Aalto, Finland
3. Fraunhofer Institute for Ceramic Technologies and Systems IKTS, Winterbergstr. 28, 01277 Dresden, Germany
4. Division of Solid State Physics and NanoLund, Lund University, P.O. Box 118, SE-22100 Lund, Sweden