JARA-Fundamentals of Future Information Technology(JARA-FIT)and RWTH Aachen University,52074 Aachen,Germany;
Peter Grünberg Institute(PGI-9),Forschungszentrum Jülich,52425 Jülich,Germany;
Key Laboratory of Semiconductor Materials Science,Institute of Semiconductors,Chinese Academy of Sciences and Beijing Key Laboratory of Low Dimensional Semiconductor Materials and Devices,Beijing 100083,China;
College of Materials Science and Opto-Electronic Technology,University of Chinese Academy of Sciences,Beijing 101804,China;