Cross sectional bright field images of sample S-30min with a PAA film on top. In panel (a) the morphology of the interface with the Si substrate is shown, depicting the presence of large nanograins between the PAA film and Si (attributed to Pt nanograins and illustrated in higher magnification in the inset of panel (a)). On top of these nanograins the alumina barrier layer usually observed at each pore bottom at the interface of PAA films with Si (in the absence of Pt in-between) is missing. Panel (b) shows another part of the sample cross section which illustrates that occasionally a continuous film of crystalline Pt exists between the PAA film and the Si substrate. The white area on the right depicts either amorphous parts of this film or Pt crystals with different orientation.