[1] Allama Iqbal Open Univ, Dept Phys, Islamabad, Pakistan
[2] Nanjing Forestry Univ, Coll Environm Sci, Nanjing, Peoples R China
[3] Shenzhen Univ, Shenzhen Key Lab Flexible Memory Mat & Devices, Coll Chem & Environm Engn,SZU NUS Collaborat Inno, Minist Educ,Int Collaborat Lab 2D Mat Optoelect S, Shenzhen 518060, Peoples R China