1. Key Laboratory of Brain‐like Neuromorphic Devices and Systems of Hebei Province College of Electronic and Information Engineering Hebei University Baoding 071002 P. R. China
2. Centre for Micro‐ and Nano‐Electronics (CMNE) School of Electrical and Electronic Engineering Nanyang Technological University Singapore 639798 Singapore
3. UMI 3288 CINTRA (CNRS‐NTU‐THALES Research Alliances) Nanyang Technological University Singapore 637553 Singapore