A change in the morphology of multilayer porous silicon with a stepwise decrease in the etching current density

We present an experimental study of multilayer porous silicon formed by electrochemical etching. Special emphasis is placed on effects that arise from a stepwise decrease in the current density while maintaining the total etching time. In order to provide a fully understanding of the morphology of the surface, we used scanning electron and atomic force microscopy. X-ray reflectivity was used to assess the porosity of porous layers. It was found that a stepwise decrease in the current density leads to the formation of a two-layer structure without changing the porosity of the base bottom layer. However, the porosity of the top layer can be varied over a wide range, which directly affects the photoluminescence of the samples. Our results show how the sample production conditions affect the fine tuning of the surface layer morphology of multilayer porous silicon.