1. Department of Electronics, Universidad de Valladolid, Paseo de Belén 15, 47011 Valladolid, Spain
2. IHP-Leibniz-Institut für Innovative Mikroelektronik, 15236 Frankfurt (Oder), Germany
3. Faculty 1 MINT-Mathematics, Computer Science, Physics, Electrical Engineering, and Information Technology, BTU Cottbus-Senftenberg, 03046 Cottbus, Germany
4. Applied Physics Department and NANOLAB USAL, Universidad de Salamanca, Plaza de la Merced s/n, 37008 Salamanca, Spain