1. Department of Electrical and Computer Engineering, University of Illinois Urbana-Champaign, Urbana, Illinois 61801, United States
2. Nick Holonyak, Jr., Micro and Nanotechnology Laboratory, University of Illinois Urbana-Champaign, Urbana, Illinois 61801, United States
3. Department of Materials Science and Engineering, University of Illinois Urbana-Champaign, Urbana, Illinois 61801, United States
4. Materials Research Laboratory, University of Illinois Urbana-Champaign, Urbana, Illinois 61801, United States
5. Beckman Institute for Advanced Science and Technology, University of Illinois Urbana-Champaign, Urbana, Illinois 61801, United States
6. Department of Physics, University of Illinois Urbana-Champaign, Urbana, Illinois 61801, United States
7. Department of Mechanical Science and Engineering, University of Illinois Urbana-Champaign, Urbana, Illinois 61801, United States