1. National Center
for Nanotechnology, King Abdulaziz City for Science and Technology, P.O. Box 6086, Riyadh 11442, Saudi Arabia
2. Laboratory of Photonics and Interfaces,
Institute of Chemical Sciences and Engineering, École Polytechnique Federale de Lausanne, Station 6, CH-1015 Lausanne, Switzerland
3. National Center for Petrochemical, King Abdulaziz City for Science and Technology, P.O. Box 6086, Riyadh 11442, Saudi Arabia
4. Physics Department, Science College, King Saud University,
P.O. Box 6086, Riyadh 11442, Saudi Arabia