1. School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798
2. Temasek Laboratories@NTU, Nanyang Technological University, Research Techno Plaza, 50 Nanyang Drive, Singapore 637553
3. Center for Integrated Research of Future Electronics (CIRFE), Institute of Materials and Systems for Sustainability (IMaSS), Nagoya University, Nagoya 464-8603, Japan