1. Electronic Technology Area, Universidad Rey Juan Carlos, Mostoles 28933, Spain
2. Gdańsk University of Technology, Faculty of Appl. Phys., Narutowicza 11/12, 80-233 Gdańsk, Poland
3. National Taiwan University, Dep. of Mat. Sci. and Eng, ., No. 1, Roosevelt Rd, Sect 4, Taipei, 106, Taiwan