1. Department of Materials Science and Engineering, University of North Texas, Denton, Texas 76203, United States
2. Department of Energy Science, Sungkyunkwan University, Suwon 16419, Republic of Korea
3. Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), Suwon 16419, Republic of Korea
4. Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, Texas 75080, United States
5. Department of Mechanical and Energy Engineering, University of North Texas, Denton, Texas 76203, United States