1. An Giang University, VNU - HCM, 18 Ung Van Khiem Street, Long Xuyen, An Giang 880000, Vietnam
2. Department of Physics, Hanoi Pedagogical University 2, Phuc Yen, Vinh Phuc 280000, Vietnam
3. Institute for Research and Development, Duy Tan University, Da Nang 550000, Vietnam