1. Faculty of Science, Physics Department, South Tehran Branch, Islamic Azad University, Tehran, Iran
2. Nanotechnology Research Center, South Tehran Branch, Islamic Azad University, Tehran, Iran
3. School of Physics, Institute for Research in Fundamental Science (IPM), P.O. Box 19395-5531, Tehran, Iran
4. Research Center for Modeling and Optimization in Science and Engineering, South Tehran Branch-Islamic Azad University, Tehran, Iran