[1] Drexel Univ, AJ Drexel Nanomat Inst, Philadelphia, PA 19104 USA
[2] Drexel Univ, Dept Mat Sci & Engn, Philadelphia, PA 19104 USA
[3] Lawrence Berkeley Natl Lab, Adv Light Source, Berkeley, CA 94720 USA
[4] Huazhong Univ Sci & Technol, Wuhan Natl Lab Optoelect, Wuhan 430074, Hubei, Peoples R China
[5] Oak Ridge Natl Lab, Mat Sci & Technol Div, Oak Ridge, TN 37831 USA
[6] Chinese Acad Sci, Beijing Natl Lab Condensed Matter Phys, Beijing 100190, Peoples R China
[7] Chinese Acad Sci, Inst Phys, Beijing 100190, Peoples R China
[8] Indiana Univ Purdue Univ, Mech & Energy Engn, Integrated Nanosyst Dev Inst, Purdue Sch Engn & Technol, Indianapolis, IN 46202 USA
[9] Johns Hopkins Univ, Dept Mat Sci & Engn, Baltimore, MD 21218 USA