1. Department of Physics, University of Patras, Patras 26504, Greece
2. Institute of Chemical Engineering Sciences, Foundation for Research and Technology Hellas (FORTH − ICE/HT), Patras 26504, Greece
3. Department of Electrical Engineering, Stanford University, Stanford, California 94305, United States
4. School of Physics, Department of Solid State Physics, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece
5. Department of Microsystems Engineering, University of Freiburg, Freiburg 79110, Germany
6. Department of Materials Science, Stanford University, Stanford, California 94305, United States
7. Precourt Institute for Energy, Stanford University, Stanford, California 94305, United States