1. Materials Science Division, Argonne National Laboratory, Lemont, IL 60439, USA.
2. School of Electronics and Information, Hangzhou Dianzi University, Hangzhou, Zhejiang 310018, China.
3. Department of Physics, Case Western Reserve University, Cleveland, OH 44106, USA.
4. Nanoscale Science and Technology Division, Argonne National Laboratory, Lemont, IL 60439, USA.
5. Advanced Photon Source, Argonne National Laboratory, Lemont, IL 60439, USA.
6. Department of Materials Science and Engineering and Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.