1. Photo-Electronic Hybrids Research Center; Korea Institute of Science and Technology (KIST); Seoul 136-791 Korea
2. Department of Polymer Science and Engineering; Inha University; Incheon 402-751 Korea
3. Department of Mechanical Engineering; Sogang University; Seoul 121-742 Korea
4. Department of Materials Science and Engineering; Massachusetts Institute of Technology; Cambridge MA 02139 USA