1. Center for Energy Harvesting Materials and Systems (CEHMS), Virginia Tech, Blacksburg, Virginia 24061, United States
2. Department of Materials Science and Engineering, Virginia Tech, Blacksburg, Virginia 24061, United States
3. Intel Corporation, Chandler, Arizona 85248, United States
4. Department of Physics and Center for Soft Matter and Biological Physics, Virginia Tech, Blacksburg, Virginia 24061, United States
5. Department of Mechanical Engineering, Virginia Tech, Blacksburg, Virginia 24061, United States
6. Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, United States
7. Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom
8. Department of Geosciences, Virginia Tech, Blacksburg, Virginia 24061, United States