1. Faculty of Microsystem Electronics and Photonics , Wroclaw University of Science and Technology , Janiszewskiego 11/17, Wroclaw , 50-372 , Poland
2. Department of Material Science and Diagnostics, Electrotechnical Institute , M. Sklodowskiej-Curie 55/61, Wroclaw , 50-369 , Poland
3. Applied Physics-Sensor Technology, Brandenburg University of Technology Cottbus-Senftenberg , Konrad-Wachsmann-Allee 17, 03046 , Cottbus , Germany