1. Physical Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal23955-6900, Saudi Arabia
2. Department of Physics, College of Sciences, Princess Nourah Bint Abdulrahman University (PNU), Riyadh11671, Saudi Arabia
3. Nanofabrication Core Lab, King Abdullah University of Science and Technology (KAUST), Thuwal23955-6900, Saudi Arabia