Scanning electron microscopy (SEM) measurements were performed on a digital field emission SEM (Ultra 55, Zeiss) with an electron beam energy of 5 keV, an aperture of 30 μm, and secondary electron detector (InLens, Zeiss). Samples were prepared by sputter coating of a PdAu alloy. The spatial elemental composition along a line was measured by energy-dispersive X-ray (EDX) spectroscopy on the same machine with an electron beam energy of 10 keV and aperture of 120 μm.