1. National Institute of Materials Physics, 405A Atomistilor Street, 077125 Magurele, Romania
2. University of Bucharest, Faculty of Physics, 405 Atomistilor Street, 077125 Magurele, Romania
3. Research Center for Instrumental Analysis SCIENT, Petre Ispirescu Street, no. 1, 077167 Tancabesti, Ilfov, Romania
4. Department of Materials Science and Engineering, Drexel University, Philadelphia, Pennsylvania 19104, United States