1. Graduate School of EEWS; Korea Advanced Institute of Science and Technology (KAIST); Daejeon 34141 Korea
2. Korea Institute of Materials Science; Changwon 51508 Korea
3. IBM T. J. Watson Research Center; Yorktown Heights NY 10598 USA
4. Department of Materials Science and Engineering; Korea Advanced Institute of Science and Technology (KAIST); Daejeon 34141 Korea