1. Department of Physics, Yeungnam University, Gyeongsan 712-749, South Korea, 38541
2. Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210; Center for High Technology Materials University of New Mexico, Albuquerque, New Mexico 87106; and SK Infrared, 801 University Blvd. SE Suite 205, Albuquerque, New Mexico 87106