MA Yan1,2, LIN Shuyu1*, XU Jie1, TANG Yifan1
(1 School of Physics and Information Technology, Shaanxi Normal University,Xi′an 710119, Shaanxi, China;2 School of Physics and Electronic Information Engineering, Engineering Research Center of Nanostructure and Functional Materials, Ningxia Normal University, Guyuan 756000, Ningxia, China)