1. Key Laboratory of Brain-Like Neuromorphic Devices and Systems of Hebei Province College of Electron and Information Engineering Hebei University Baoding 071002 China
2. Jiangsu Province Special Equipment Safety Supervision and Inspection Institute Branch of Wuxi National Quality Supervision and Inspection Center of Graphene Products Wuxi Jiangsu 214174 China
3. Department of Materials Science and Engineering National University of Singapore Singapore 117576 Singapore