1. Department of Materials Science, Institute for Surface Science and Corrosion (LKO), University of Erlangen‐Nuremberg, Martensstrasse 7, 91058 Germany, Fax: +49‐9131‐852‐7582
2. Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2‐1 Yamada‐oka, Suita, Osaka 565‐0871 Japan