[1] Univ Calif Berkeley, Lawrence Berkeley Natl Lab, Adv Light Source, Berkeley, CA 94720 USA
[2] Chinese Acad Sci, Shanghai Inst Microsyst & Informat Technol, State Key Lab Funct Mat Informat, Shanghai 200050, Peoples R China
[3] ShanghaiTech Univ, Sch Phys Sci & Technol, Shanghai 200031, Peoples R China
[4] Univ Calif Berkeley, Lawrence Berkeley Natl Lab, Div Chem Sci, Berkeley, CA 94720 USA