1. Department of Electrical Engineering and Automation, School of Electrical Engineering, Aalto University, PO Box 13500, 00076 Aalto, Finland
2. Department of Applied Physics, School of Science, Aalto University, PO Box 15100, 00076 Aalto, Finland
3. Department of Physics, University of Jyväskylä, PO Box 35, FI-40014 Jyväskylä, Finland
4. Department of Chemistry and Materials Science, School of Chemical Engineering, Aalto University, PO
Box 16100, 00076 Aalto, Finland