State Key Laboratory of Functional Materials for Informatics;
Shanghai Institute of Microsystem and Information Technology;
Chinese Academy of Sciences;
Shanghai 200050;
School of Electronic Science and Engineering;
Nanjing University;
Nanjing 210093;
Department of Information Science and Electronic Engineering;
Zhejiang University;
Hangzhou 310027;
Peter Grunberg Institute 9;
Forschungszentrum Julich and 3ARA Fundamentals of Future Intormation Technology;
Julich 52425;
Germany;
