[1] Brookhaven Natl Lab, Ctr Funct Nanomat, Upton, NY 11973 USA
[2] Arizona State Univ, Dept Phys, Tempe, AZ 85287 USA
[3] So Connecticut State Univ, Dept Phys, New Haven, CT 06515 USA
[4] McMaster Univ, Dept Mat Sci & Engn, Hamilton, ON L8S 4L7, Canada
[5] McMaster Univ, Canadian Ctr Electron Microscopy, Hamilton, ON L8S 4L7, Canada
[6] Yale Univ, Dept Appl Phys, New Haven, CT 06520 USA
[7] Yale Univ, Ctr Res Interface Struct & Phenomena, New Haven, CT 06520 USA