1. School of Materials Science Japan Advanced Institute of Science and Technology 1‐1 Asahidai, Nomi Ishikawa 923‐1292 Japan
2. Physics Department Faculty of Science Minia University 11432 Main Road—Shalaby Land Minia 61519 Egypt
3. Nanoelectronics Research Institute National Institute of Advanced Industrial Science and Technology (AIST) 16‐1 Onogawa Tsukuba 305‐8569 Japan
4. Hitachi Cambridge Laboratory Hitachi Europe Ltd. J. J. Thomson Avenue Cambridge CB3 0HE UK