1. Institute of High Performance Computing, A*STAR, Singapore 138632, Singapore
2. National Laboratory of Solid State Microstructures, College of Engineering and Applied Sciences, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
3. Department of Science, Borough of Manhattan Community College, The City University of New York, New York, New York 10007, United States
4. Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States
5. Texas Instruments, Dallas, Texas 75243, United States
6. Center for Multidimensional Carbon Materials, Institute for Basic Science, Ulsan National Institute of Science and Technology, Ulsan 689-798, Korea