1. Gangneung Center, Korea Basic Science Institute, Gangneung 210-702, South
Korea
2. Department of Materials
Science
and Engineering, Frederick Seitz Materials Research Laboratory, and
Beckman Institute, University of Illinois at Urbana−Champaign, Illinois 61801, United States
3. Sandia National Laboratories, Albuquerque,
New Mexico 87185, United States
4. Sandia National Laboratories, Livermore, California 94550, United States