1. Department of Physics, College of Science, UAE University, P. O. Box 15551, Al-Ain, United Arab Emirates
2. National Water and Energy Center, UAE University, P. O. Box 15551, Al-Ain, United Arab Emirates
3. Department of Physics, Konkuk University, Seoul 05029, Republic of Korea
4. School of Science and Technology, University of New England, Armidale, New South Wales 2351, Australia
5. Department of Materials Science and Engineering, University of Toronto, Toronto, Ontario M5S 3E4, Canada