1. Institute for Clean Energy and Advanced Materials, School of Materials and Energy, Southwest University, Chongqing Key Laboratory for Advanced Materials and Technologies of Clean Energy, Chongqing 400715, P. R. China
2. College of Physics and Electronics Engineering, Chongqing Normal University, Chongqing 401331, P. R. China
3. Electronic & Magnetic Materials Department, Advanced Materials Division, Central Metallurgical Research and Development Institute (CMRDI), P.O. Box 87, Helwan, Cairo 11421, Egypt
4. School of Physics and Electronic Science, Zunyi Normal College, Zunyi 563002, P. R. China