Raman scattering study of microstructure of n-type porous silicon

We report a detailed Raman scattering study of porous silicon film prepared on n-type silicon substrate. We observe large enhancement of Raman scattered signal and also that with increase in laser power the Raman line shape shows low frequency asymmetry, decrease in frequency of the peak position and reduction in signal enhancement. Our results could be explained consistently only by considering a two layered model of the microstructure of these films. We argue that this is a simple and non-destructive technique to look at the layered nature of the microstructure of these materials-so far seen only by high resolution electron microscopy