1. National Institute for Research and Development in Microtechnologies, Erou Iancu Nicolae Street 126A, 077190 Voluntari, Ilfov, Romania
2. Physics Faculty, University of Bucharest, 077125 Bucharest, Ilfov, Romania
3. Academy of Romanian Scientists, Str. Ilfov, Nr. 3, 050044 Bucharest, Ilfov, Romania