1. Department of Materials Science and Engineering and California Nano Systems Institute, University of California, Los Angeles, California 90095, United States
2. Department of Mechanical Engineering, School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan
3. Canatu, Ltd., Konalankuja 5, FI-00390 Helsinki, Finland
4. Department of Applied Physics, Aalto University School of Science, FI-00076 Aalto, Finland
5. Energy Nano Engineering Laboratory, National Institute of Advanced Industrial Science and Technology (AIST), Ibaraki 305-8564, Japan