1. Shenzhen Engineering Laboratory of Phosphorene and Optoelectronics; Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province; College of Optoelectronic Engineering; Shenzhen University; Shenzhen 518060 P. R. China
2. Department of Nanoscience and Technology; Bharathiar University; Coimbatore 641046 India