1. Department of Materials Science and Engineering, University of California, Berkeley, Berkeley, CA 94720, USA.
2. Materials Science and Engineering Program, Department of Mechanical Engineering, University of California, Riverside, Riverside, CA 92521, USA.
3. Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, Berkeley, CA 94720, USA.
4. Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA.