Maskless Cu patterning on porous silicon (PS) assisted by a focused laser beam is demonstrated. Cu was selectively electroplated only at the illuminated part of PS by utilizing the rectifying properties of the Schottky barrier formed at a p-type semiconductor/solution interface. Applying this principle, Cu deposition was achieved in the presence of Cl- ions necessary for inhibition of the immersion plating reaction. (C) 2004 The Electrochemical Society.