1. State Key Laboratory of Solidification Processing; Center for Nano Energy Materials; School of Materials Science and Engineering; Northwestern Polytechnical University and Shaanxi Joint Laboratory of Graphene (NPU); Xi'an 710072 China
2. Department of Materials Science and Nano Engineering; Rice University; Houston TX 77050 USA
3. University Research Facility in Materials Characterization and Device Fabrication; The Hong Kong Polytechnic University; Hong Kong 999077 China
4. Department of Mechanical Engineering; University of Delaware; Newark NJ, DE 19716 USA