[1] Argonne Natl Lab, Div Mat Sci, Argonne, IL 60439 USA
[2] Argonne Natl Lab, Ctr Nanoscale Mat, Argonne, IL 60439 USA
[3] Univ Penn, Dept Mech Engn & Appl Mech, Philadelphia, PA 19104 USA
[4] Univ Penn, Dept Mat Sci & Engn, Philadelphia, PA 19104 USA
[5] Univ Wisconsin, Dept Elect & Comp Engn, Madison, WI 53706 USA
[6] Argonne Natl Lab, Ctr Electron Microscopy, Argonne, IL 60439 USA