1. Department of Materials Science and Engineering, Michigan Technological University, Houghton, Michigan 49931
2. Department of Electronics and Nanoengineering, School of Electrical Engineering, Aalto University, Espoo FI-00076, Finland
3. Department of Chemistry and Materials Science, School of Chemical Engineering, Aalto University, Espoo FI-00076, Finland
4. Department of Electrical and Computer Engineering, Michigan Technological University, Houghton, Michigan 49931