1. Department of Materials Science and Engineering, University of California, Los Angeles, Los Angeles, California 90095-1595, United States
2. Department of Mechanical and Aerospace Engineering and the Andlinger Center for Energy and the Environment, Princeton University, Princeton, New Jersey 08544-5263, United States
3. Department of Materials Science and Engineering, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan, ROC
4. Department of Chemical and Biomolecular Engineering, University of California, Los Angeles, Los Angeles, California 90095-1592, United States
5. California NanoSystems Institute, University of California, Los Angeles, Los Angeles, California 90095, United States