1. National Institute of Materials Physics, 077125 Magurele, Ilfov, Romania
2. University of Bucharest, Faculty of Physics, Materials
and Devices for Electronics and Optoelectronics Research Center, 077125 Magurele,
Ilfov, Romania
3. OPTOELECTRONICA − 2001 S.A., 077125 Magurele, Ilfov, Romania
4. School
of Science and Engineering, Reykjavik University, Menntavegur 1, IS-101 Reykjavik, Iceland