Abstract

 Electron microscopy investigation of aged Porous Silicon reveáis for the first time a surface with two different superimposed layers. These layers are not present in freshly prepared samples. The study was performed by means of a Field-Emission Scanning Electron Microscope. The photomicrographs show that the porous skeleton has a fractal-like self-standing arrangement. Skeleton columns with fluctuating diameters from 20 nm are detectable in the lowest layer. Porous growth direction is preferentially perpendicular to the surface. In addition, Energy Dispersive Spectroscopy reveáis that the porous layer is composed mainly of Silicon. The observed nanostructure is consistent with a model based on wires of fluctuating width. This model can also explain the recombination dynamics of Porous Silicon. The relation between the structure and this model [20] is discussed.