作者机构:Key Laboratory for Wide Band Gap Semiconductor Materialand Devices of Education, School of Microelectronics,Xidian University, Xi'an 710071, China
相关基金:This work is supported by the Project of National Natural Science Foundation of China (Grant Nos. 61376099, 11235008, 61434007) and the Specialized Research Fund for the Doctoral Program of High Education (Grant No. 20130203130002).Acknowledgments The authors are grateful to Dr.YaoZhi-Binand Dr.HeBao-Ping at the Northwest Institute of Nuclear Technology,who provided help in setting up 60^Co Source Facility.