[1] Zhejiang Normal Univ, Dept Phys, Jinhua 321004, Zhejiang, Peoples R China
[2] Zhejiang Inst Photoelect, Jinhua 321004, Zhejiang, Peoples R China
[3] Abbottabad Univ Sci & Technol, Dept Phys, POB 22500, Havellian, Khyber Pakhtunk, Pakistan
[4] Univ Malakand, Dept Phys, Chakdara, Khyber Pakhtunk, Pakistan