1. Materials Science and EngineeringPhysical Science and Engineering DivisionKing Abdullah University of Science and Technology (KAUST) Thuwal 23955‐6900 Saudi Arabia
2. Physics DepartmentFaculty of ScienceKing Abdulaziz University Jeddah 21589 Saudi Arabia
3. Center of NanotechnologyKing Abdulaziz University Jeddah 21589 Saudi Arabia