1. Department of Materials Science and Engineering and A. J. Drexel Nanomaterials Institute Drexel University Philadelphia Pennsylvania 19104
2. College of Materials Science and Engineering Nanjing Tech University Nanjing 210009 China
3. Materials Science and Technology Division Oak Ridge National Laboratory Oak Ridge Tennessee 37381
4. Thin Film Physics Division Department of Physics, Chemistry and Biology (IFM) Linköping University SE‐583 31 Linköping Sweden