1. Department of Nano Systems Engineering, Center for Nano Manufacturing, Inje University, Gimhae 621-749, Korea
2. ATTO Co., Ltd., Shiheung 429-849, Korea
3. Department of Physics, Kyung Hee University, Seoul 130-701, Korea
4. Department of Information Materials Science and Engineering, Chonbuk University, Jeonju 664-14, Korea
5. Department of Physics, Yeungnam University, Gyeongsan 712-749, Korea