Abstract: Structured surface, having a support layer and, connected electrically to it, peak-shaped elements each peak-shaped element exhibiting a cylindrical or conical shaped stem region adjacent to the support layer and at least two, preferably 2 to 4 peaks at the free end of the stem region. The structured surface is suitable in particular as electron emission source for ultra-flat image screens, for electron lithography or for scanning or transmission microscopy.

Abstract: A process for producing an oxide layer with a pore structure on the surface of a strip or wire of aluminum or an aluminum alloy is such that the strip or wire is passed continuously through an electrolyte and simultaneously anodized under conditions that create pores and at an anodizing voltage creating the desired thickness of oxide layer. In a first stage of the process, in order to form a fine pore structure, the anodizing voltage is set at an initial level (U.sub.1) and subsequently, in a second stage to form a coarser pore structure, raised to a final level (U.sub.2) required to reach the desired thickness of oxide layer.