The geometric surface area of the Au POSCs were determined after the growth from SEM images of the entire POSC. Since the diameter of the wire is known, one can determine the diameter of the bead on a horizontal and vertical axis. Usually, the vertical diameter is larger than the horizontal diameter. Assuming that the POSC is a sphere, the surface area was calculated from the average diameter from the horizontal and vertical axis. Finally, the area of the Au wire in contact with the POSC was subtracted from the surface area of the bead (0.785 mm 2 ). The resulting surface areas for the POSCs ranged from 0.178 cm 2 to 0.322 cm 2 . All current densities given refer to the geometric surfaces of the POSCs. mogeneous in most cases, the NPG films show a strong dependence on the crystallographic orientation. Both very thin and thick NPG films tend to exfoliate.