1. Department of Materials Science and Engineering, University of North Texas, Denton, Texas 76203, United States
2. Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Sungkyunkwan University, Suwon 16419, Republic of Korea
3. Department of Energy Science, Sungkyunkwan University, Suwon 16419, Republic of Korea
4. Department of Mechanical and Energy Engineering, University of North Texas, Denton, Texas 76203, United States