1. Department
of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544, United States
2. State
Key Laboratory of Superlattices and Microstructures, Institute of
Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, China
3. Material
Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
4. Program
in Applied and Computational Mathematics and the Andlinger Center
for Energy and the Environment, Princeton University, Princeton, New Jersey 08544, United States