1. International Laboratory of Environmental Electronic Devices (LAIDEA UNAM) ENES Morelia National Autonomous University of Mexico 58190 Morelia Mexico
2. Institute of Solid-State Physics Faculty of Physics and Electrical Engineering University of Bremen 28359 Bremen Germany
3. Micro- and Nanotechnology Research Centre MICRONA Veracruz University 94294 Veracruz Mexico
4. Institute of Environmental Physics Faculty of Physics and Electrical Engineering University of Bremen 28359 Bremen Germany
5. MAPEX Center of Materials and Processes University of Bremen 28359 Bremen Germany