1. Department of Materials Science & 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