1. Materials Laboratory, Department of Physics, COMSATS University Islamabad, Park Road, 45500 Islamabad, Pakistan
2. Micro and Nanotechnology Program, Middle East Technical University, 06800 Ankara, Turkey
3. Center for Solar Energy Research and Applications (GÜNAM), Middle East Technical University, 06800 Ankara, Turkey
4. Department of Physics, Middle East Technical University, 06800 Ankara, Turkey