1. Department of Materials Science and Engineering, Drexel University, Philadelphia, Pennsylvania 19104, United States
2. A. J. Drexel Nanomaterials Institute, Drexel University, Philadelphia, Pennsylvania 19104, United States
3. Thin Film Physics Division, Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-581 83 Linköping, Sweden
4. Physics Department, Nuclear Research Centre − Negev, 84190 Beer-Sheva, Israel