1. National Institute for Research and Development in Microtechnology (IMT-Bucharest), 126A Erou Iancu Nicolae Street, Voluntari 077190, Romania
2. Faculty of Physics, University of Bucharest, 405 Atomistilor Street, Magurele 07712, Romania
3. Faculty of Chemistry, University of Bucharest, 90-92 Panduri Street, Bucharest 050663, Romania