1. Department of Physics Abbottabad University of Science and Technology Havelian Khyber Pakhtunkhwa Pakistan
2. Department of Physics Beijing Normal University Beijing China
3. Department of Physics University of Azad Jammu and Kashmir 13100 Muzaffarabad Pakistan
4. National Centre for Physics Islamabad Pakistan
5. School of Chemistry and Chemical Engineering Beijing Institute of Technology Beijing 100081 China
6. Key Laboratory of Optoelectronic Devices and Systems of Guangdong Province & Ministry of Education College of Physics and Optoelectronic Engineering Shenzhen University Shenzhen 518060 China