1. Department of Applied Physics, University of Barcelona, C/Martí i Franquès, 1, Barcelona, Catalunya 08028, Spain
2. ENPHOCAMAT Group, Institute of Nanoscience and Nanotechnology (IN2UB), University of Barcelona, C/Martí i Franquès, 1, Barcelona, Catalunya 08028, Spain
3. Escuela de Física, Universidad Industrial de Santander, Carrera 27 calle 9 Ciudad Universitaria, Bucaramanga 68002, Colombia