1. Research Center for Applied Sciences, Academia Sinica, Taipei 115, Taiwan
2. Department of Materials Science and Engineering, National Tsing Hua University, Hsin-Chu 300, Taiwan
3. Analysis Laboratory, ULVAC-PHI, Inc., Chigasaki 253-8522, Japan
4. Center for Nanotechnology, Materials Science, and Microsystems, National Tsing Hua University, Hsin-Chu 300, Taiwan
5. Department of Materials Science and Engineering, National Taiwan University, Taipei 106, Taiwan