1. AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, Al. Mickiewicza 30, 30-059 Krakow, Poland
2. S3, Istituto Nanoscienze-CNR, Via Campi 213/a, 41125 Modena, Italy
3. Department of Physics, Informatics and Mathematics, University of Modena and Reggio Emilia, Via Campi 213/a, 41125 Modena, Italy