Scanning electron microscopy (SEM) images were obtained on a Philips XL30 FEG in secondary electron mode. Accelerating voltage, magnification, and working distance are given in the figures. Energy Dispersive X-ray (EDX) measurements were made in the same apparatus (SUTW, Sapphire, EDAX CDU TM LEAD TM detector). An amplification time of 100 µs has been used and an acquisition time of 60 s, leading to an energy resolution of around 135 eV.